0001193125-26-304966 | S-4 | XBRL Viewer

LEASES - Schedule of Future Minimum Annual Lease Payments (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Leases [Abstract]
2026	$ 106
2027	84
Thereafter	0
Total lease payments	190
Less: imputed discount rate	(14)
Carrying value of operating lease liabilities	$ 176	$ 154

Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) $ in Thousands	12 Months Ended
	Dec. 31, 2024 USD ($)
Statement of Stockholders' Equity [Abstract]
Offering costs	$ 268

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	COMMON	ADDITIONAL PAID-IN CAPITAL	ACCUMULATED DEFICIT	ACCUMULATED OTHER COMPREHENSIVE GAIN (LOSS)
Beginning Balance (in shares) at Dec. 31, 2023		4,728,674
Beginning Balance at Dec. 31, 2023	$ 106,184	$ 4	$ 341,410	$ (235,245)	$ 15
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from a securities purchase agreement, net of offering costs (in shares)		454,545
Issuance of common stock from a securities purchase agreement, net of offering costs of $268	5,137		5,137
Issuance of common stock under the stock purchase plan (in shares)		7,603
Issuance of common stock under the stock purchase plan	62		62
Issuance of common stock under the stock award plan		241
Forfeiture of restricted common stock (in shares)		(2,320)
Forfeiture of restricted common stock	0
Share-based compensation	7,993		7,993
Net loss	(57,775)			(57,775)
Other comprehensive gain	53				53
Ending Balance (in shares) at Dec. 31, 2024		5,188,743
Ending Balance at Dec. 31, 2024	61,654	$ 4	354,602	(293,020)	68
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from a securities purchase agreement, net of offering costs (in shares)		12,736
Share-based compensation	1,879		1,879
Net loss	(9,439)			(9,439)
Other comprehensive gain	(21)				(21)
Ending Balance (in shares) at Mar. 31, 2025		5,201,479
Ending Balance at Mar. 31, 2025	54,073	$ 4	356,481	(302,459)	47
Beginning Balance (in shares) at Dec. 31, 2024		5,188,743
Beginning Balance at Dec. 31, 2024	61,654	$ 4	354,602	(293,020)	68
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under the stock purchase plan (in shares)		7,258
Issuance of common stock under the stock purchase plan	$ 16		16
Issuance of common stock under the stock award plan	0	87,320
Share-based compensation	$ 5,314		5,314
Net loss	(8,978)			(8,978)
Other comprehensive gain	(50)				(50)
Ending Balance (in shares) at Dec. 31, 2025		5,283,321
Ending Balance at Dec. 31, 2025	$ 57,956	$ 4	359,932	(301,998)	18
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock under the stock purchase plan (in shares)		6,354
Issuance of common stock under the stock award plan	561	561
Issuance of common stock under the stock award plan	$ 3		3
Share-based compensation	613		613
Net loss	(8,278)			(8,278)
Other comprehensive gain	(17)				(17)
Ending Balance (in shares) at Mar. 31, 2026		5,290,236
Ending Balance at Mar. 31, 2026	$ 50,277	$ 4	$ 360,548	$ (310,276)	$ 1

RESTRUCTURING AND SEVERANCE - Narrative (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended
	May 02, 2025	Feb. 29, 2024	Mar. 31, 2026	Jun. 30, 2025	Mar. 31, 2024
Restructuring Cost and Reserve [Line Items]
Positions eliminated (as a percent)	40.00%	45.00%
Restructuring costs incurred			$ 2.3	$ 1.7	$ 3.3
Research and development
Restructuring Cost and Reserve [Line Items]
Restructuring costs incurred			1.6	1.2	2.0
General and administrative
Restructuring Cost and Reserve [Line Items]
Restructuring costs incurred			$ 0.7	$ 0.5	$ 1.3

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References + Details

LEASES - Additional Information (Details) $ in Millions	12 Months Ended
LEASES - Additional Information (Details) $ in Millions	Dec. 31, 2025 USD ($) ft²	Dec. 31, 2024 USD ($)
Operating Leased Assets [Line Items]
Operating lease, weighted average remaining lease term	1 year 9 months
Office
Operating Leased Assets [Line Items]
Area of real estate property \| ft²	4,500
Operating lease, weighted average discount percent	9.00%
Operating lease, expense	$ 0.2	$ 0.2
Lease payments	$ 0.2	$ 0.3

BALANCE SHEET COMPONENTS

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Balance Sheet Related Disclosures [Abstract]

BALANCE SHEET COMPONENTS

BALANCE

SHEET COMPONENTS

Prepaid expenses and other current assets —

Prepaid expenses and other current assets consisted of the following as of March 31, 2026 and December 31, 2025:


(in thousands)	MARCH 31, 2026		DECEMBER 31, 2025
Research and development	$	595	$	3,372
Insurance		231		409
Other prepaids		135		219
Other current assets		5,734		2,517

	$	6,695	$	6,517

Other current assets consists of approximately $3.4 million of accounts receivable related to clinical development costs expected to be returned to the Company in the second quarter of 2026, approximately $2.2 million related to a contingent payment receivable tied to a Phase 1 clinical study milestone in connection with the JV Sale, approximately $0.1 million of interest income and other current assets.

Accrued Expenses —

Accrued expenses consisted of the following as of March 31, 2026 and December 31, 2025:


(in thousands)	MARCH 31, 2026		DECEMBER 31, 2025
Compensation and related expenses	$	1,407	$	2,334
Professional fees		1,396		1,039
Research and development		94		394
Other accrued expenses		204		24

	$	3,101	$	3,791

6. BALANCE SHEET COMPONENTS

Property and Equipment—

Property and equipment consisted of the following as of December 31, 2025 and 2024:


(in thousands)	DECEMBER 31, 2025			DECEMBER 31, 2024
Computer and other equipment	$	191		$	191
Capitalized software		89			89
Furniture and fixtures		76			151
Leasehold improvements		147			338

Total property and equipment		503			769
Less: accumulated depreciation		(480	)		(654	)

Total property and equipment—net	$	23		$	115

Depreciation expense totaled $0.1 million for both years ended December 31, 2025 and 2024.

Prepaid Expenses and Other Assets—

Prepaid expenses and other assets consisted of the following as of December 31, 2025 and 2024:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Research and development	$	3,372	$	697
Insurance		409		424
Other prepaids		219		214
Other current assets		2,517		995

	$	6,517	$	2,330

Accrued Expenses—

Accrued expenses consisted of the following as of December 31, 2025 and 2024:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Research and development	$	394	$	1,197
Compensation and related expenses		2,334		3,095
Professional fees		1,039		510
Other		24		160

	$	3,791	$	4,962

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION (Policies)

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Accounting Policies [Abstract]

Unaudited Financial Information

Unaudited Financial Information—

The unaudited condensed consolidated financial statements of the Company have been prepared in conformity with accounting principles generally accepted in the United States of America (“GAAP”), and pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) promulgated by the Financial Accounting Standards Board.

In the opinion of the Company, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the financial position and results of operations for the reported interim periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure. The results of operations for interim periods are not necessarily indicative of results to be expected for the full year or any other interim period.

The accompanying unaudited condensed consolidated financial statements include the accounts of Rallybio Corporation and its subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

These accompanying unaudited condensed consolidated financial statements and notes should be read in conjunction with Rallybio’s Annual Report on Form

10-K

for the year ended December 31, 2025 (our “Annual Report”). The Company’s significant accounting policies are described in Note 2 of the Notes to the consolidated financial statements included in our Annual Report. There have been no new accounting policies, including the adoption of new accounting standards during the three months ended March 31, 2026, unless otherwise noted below, which could be expected to materially impact the Company’s unaudited condensed consolidated financial statements.

Future Milestone and Royalty Assets

As part of the JV Sale, the Company received consideration including an estimated $3.0 million in future contingent milestones and royalty payments, which are recognized as a contingent consideration asset on the condensed consolidated balance sheets. The fair value of this contingent consideration was determined using a model that incorporates significant unobservable inputs based on Company estimates, external data, and management’s judgment and forecasts. Key assumptions in the model include the discount rate, the timing of expected cash flows, the probability of achieving the milestone and royalty payments, and projected future net revenues.

The Company periodically reviews the carrying value of the contingent consideration when impairment indicators arise and records an impairment loss if the carrying amount materially exceeds the reassessed fair value. Increases in the carrying value are recognized only when contingent gains are realized. Since the contingent payments are tied to Phase 1 clinical study milestones and future royalty payments, the Company believes the likelihood of timely payment by Recursion is uncertain.

Future Milestone and Royalty Assets

As part of the JV Sale, the Company received consideration including an estimated $3.0 million in future contingent milestones and royalty payments, which are recognized as a contingent consideration asset within prepaid expenses and other current assets on the consolidated balance sheets. The fair value of this contingent consideration was determined using a model that incorporates significant unobservable inputs based on Company estimates, external data, and management’s judgment and forecasts. Key assumptions in the model include the discount rate, the timing of expected cash flows, the probability of achieving the milestone and royalty payments, and projected future net revenues.

The Company periodically reviews the carrying value of the Contingent Consideration when impairment indicators arise and records an impairment loss if the carrying amount materially exceeds the reassessed fair value. Increases in the carrying value are recognized only when contingent gains are realized. Since the contingent payments are tied to Phase 1 clinical study milestones and future royalty payments, the Company believes the likelihood of timely payment by Recursion is remote. See Note 9, “Investment in Joint Venture” for additional details.

Recently Issued Accounting Pronouncements

—In November 2024, the FASB issued ASU

2024-03,

Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic

220-40):

Disaggregation of Income Statement Expenses (

“ASU

2024-03”).

This ASU requires public entities to disclose additional transparency on certain costs and expenses. ASU

2024-03

is effective for annual periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. Early adoption is permitted. The Company has chosen not to early adopt this standard and is currently evaluating the potential impact of adopting this standard on its financial statements.

Recently Adopted Accounting Pronouncements

—In December 2023, the FASB issued, ASU

2023-09,

Income Taxes (Topic 740):

Improvements to Income Tax Disclosures

(“ASU

2023-09”)

which establishes new income tax disclosure requirements in addition to modifying and eliminating certain existing requirements. The ASU is effective for public business entities for fiscal years beginning on or after December 15, 2024 with early adoption permitted. The amendments in ASU

2023-09

were early adopted by the Company on a prospective basis. There was no material impact to the Company’s financial statements as a result of adopting ASU

2023-09.

See Note 8, “Income Taxes” for additional detail.

In May 2025, the FASB issued ASU

2025-03,

Business Combinations (Topic 805) and Consolidation (Topic 810):

Determining the Accounting Acquirer in the Acquisition of a Variable Interest Entity

(“ASU

2025-03”),

which revises current guidance for determining the accounting acquirer for a transaction effected primarily by exchanging equity interests in which the legal acquiree is a variable interest entity that meets the definition of a business. The amendments require that an entity consider the same factors that are currently required for determining which entity is the accounting acquirer in other acquisition transactions. The Company early adopted this ASU on a prospective basis as of October 1, 2025. There was no material impact to the Company’s financial statements as a result of adopting ASU

2025-03.

Recently Issued Accounting Pronouncements

—In November 2024, the FASB issued ASU

2024-03,

Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic

220-40):

Disaggregation of Income Statement Expenses (

“ASU

2024-03”).

This ASU requires public entities to disclose additional transparency on certain costs and expenses. ASU

2024-03

Basis of Presentation

Basis of Presentation—

The accompanying consolidated financial statements of the Company have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”), and pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Any reference in these notes to applicable guidance is meant to refer to GAAP as found in the Accounting Standards Codification (“ASC”) and Accounting Standards Updates (“ASU”) promulgated by the Financial Accounting Standards Board (“FASB”).

In the opinion of the Company, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the financial position and results of operations for the reported periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.

On February 6, 2026, the Company executed a reverse stock split of its issued and outstanding common stock, par value $0.0001, at a ratio of

1-for-8

with a record date of December 30, 2025 (the “Reverse Stock Split”). All common share, per share and related information included in the accompanying financial statements and footnote disclosures have been adjusted retroactively, where applicable, to reflect the Reverse Stock Split. See Note 14, “Subsequent Events” for additional details.

Principles of Consolidation

—The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

—The preparation of the Company’s consolidated financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts and disclosures

in the consolidated financial statements. While management believes that estimates and assumptions used in the preparation of the consolidated financial statements are appropriate, actual results could differ from those estimates. The most significant estimates are those used in the determination of the fair value of its common units and incentive units awarded to employees prior to the Company’s initial public offering (“IPO”), for purposes of recording share-based incentive compensation, the fair value of stock options, as well as contracted research and development expenses incurred.

Liquidity and Ability to Continue as a Going Concern

—The accompanying consolidated financial statements have been prepared assuming that the Company will continue as a going concern. Management has evaluated whether there are conditions and events that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the financial statements are issued. Since its inception, the Company has incurred net losses and negative cash flows from operations.

During the years ended December 31, 2025 and 2024, the Company incurred a net loss of $9.0 million and $57.8 million, respectively. The loss for the year ended December 31, 2025 included a $23.0 million gain in connection with the JV Sale in 2025. In addition, as of December 31, 2025, the Company had an accumulated deficit of $302.0 million. The Company expects to continue to generate operating losses and negative cash flows in the foreseeable future.

The Company had cash, cash equivalents and marketable securities of $54.7 million as of December 31, 2025. The Company currently expects that its cash, cash equivalents and marketable securities will be sufficient to fund its operating expenses and capital requirements for more than 12 months from the date these consolidated financial statements are issued. However, the Company does not anticipate that its current cash, cash equivalents and marketable securities as of December 31, 2025 will be sufficient to fund any of its product candidates through regulatory approval, and it will need to raise substantial additional capital to complete the development and commercialization of its product candidates, if approved. Rallybio may satisfy its future cash needs through the sale of equity securities, debt financings, corporate collaborations or license agreements, working capital lines of credit, grant funding, interest income earned on invested cash balances or a combination of one or more of these sources.

Collaboration Arrangements

—The Company considers the nature and contractual terms of an arrangement to assess whether an arrangement involves a joint operating activity that expose two or more parties to significant risks and rewards dependent on the commercial success of the activity. If the Company is an active participant and is exposed to significant risks and rewards dependent on the commercial success of the activity, the Company accounts for such arrangement as a collaborative arrangement under ASC 808,

Collaborative Arrangements

(“ASC 808”). ASC 808 describes arrangements within its scope and considerations surrounding presentation and disclosure, with recognition matters subjected to other authoritative guidance, in certain cases by analogy.

For arrangements determined to be within the scope of ASC 808 for certain research and development activities where a collaborative partner is not a customer following the guidance of ASC 606,

Revenue Recognition

(“ASC 606”), the Company accounts for payments due to a collaboration partner as research and development expense and for payments owed to us from our collaboration partner for the reimbursement of research and development costs as a contra-expense in the period such expenses are incurred. The Company classifies payments owed or receivables recorded as other current liabilities and other current assets, respectively, in the Company’s consolidated balance sheets. See Note 3, “Collaboration and License Agreements” for additional details.

Asset Acquisitions

—The Company evaluates acquisitions of assets and other similar transactions to assess whether or not the transaction should be accounted for as a business combination or asset acquisition by first applying a screen test to determine whether substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable asset or group of similar identifiable assets. If this screen criteria is met, the transaction is accounted for as an asset acquisition. If not, further determination is required as to whether or not the Company has acquired inputs and processes that have the ability to create outputs, which would meet the definition of a business.

The Company measures and recognizes asset acquisitions that are not deemed to be business combinations based on the cost to acquire the assets, which includes transaction costs. In an asset acquisition, the cost allocated to acquire

in-process

research and development (“IPR&D”) with no alternative future use is charged to research and development expense at the acquisition date. See Note 3, “Collaboration and License Agreements” for additional details.

Variable Interest Entity

—The Company evaluates its ownership, contractual, and other interests in entities to determine if it has any variable interest in a variable interest entity (“VIE”). These evaluations are complex, involve judgment, and the use of estimates and assumptions based on available historical information, among other factors. If the Company determines that an entity in which it holds a contractual, or ownership, interest is a VIE and that the Company is the primary beneficiary, the Company consolidates such entity in its consolidated financial statements. The primary beneficiary of a VIE is the party that meets both of the following criteria: (i) has the power to make decisions that most significantly affect the economic performance of the VIE; and (ii) has the obligation to absorb losses or the right to receive benefits that in either case could potentially be significant to the VIE. Management performs ongoing reassessments of whether changes in the facts and circumstances regarding the Company’s involvement with a VIE will cause the consolidation conclusion to change. Changes in consolidation status are applied prospectively. The Company evaluated its investment in RE Ventures I, LLC, a limited liability company

(“REV-I”),

defined in Note 9, and concluded that it represented a VIE and the Company was not deemed the primary beneficiary. If the Company is not deemed to be the primary beneficiary in a VIE, the Company accounts for the investment or other variable interests in a VIE in accordance with the applicable GAAP. See Note 9, “Investment in Joint Venture” for additional details.

Equity Method Investments

—The Company accounts for investments for which it does not have a controlling interest in accordance with ASC 323,

Investments—Equity Method and Joint Ventures

(“ASC 323”). The Company recognizes its

pro-rata

share of income and losses in “loss on investment in joint venture” on the consolidated statements of operations and comprehensive loss, with a corresponding change to the investment in joint venture asset on the consolidated balance sheets.

Financial Instruments

—The Company’s principal financial instruments are comprised of cash, cash equivalents, available for sale marketable securities, accounts payable and accrued liabilities. The carrying value of all financial instruments approximates fair value.

Concentrations of Credit Risk

—Financial instruments that potentially subject the Company to significant concentration of credit risk consist primarily of cash, cash equivalents and marketable securities. The Company invests its excess cash in money market funds and marketable securities in government insured financial institutions that are subject to minimal credit and market risk. Management believes that the Company is not exposed to significant credit risk as the Company’s deposits are held at financial institutions that management believes to be of high credit quality, and the Company has not experienced any losses on these deposits.

Cash and Cash Equivalents

—The Company classifies amounts on deposit in banks and cash invested temporarily in various instruments, primarily money market funds, with original maturities of three months or less at the time of purchase as cash and cash equivalents. The carrying amounts reported on the consolidated balance sheets represent the fair values of cash and cash equivalents.

Marketable Securities

—We invest our excess cash balances in highly rated United States (“U.S.”) government-backed debt securities and treasuries. We classify our marketable securities as

available-for-sale

and accordingly, record such securities at fair value. Debt securities with original maturities of greater than 90 days are classified as

available-for-sale

marketable securities and debt securities with original maturities of less than 90 days from the date of purchase are classified as cash equivalents.

Unrealized gains and losses on our marketable debt securities that are deemed temporary are included in accumulated other comprehensive gain (loss) as a separate component of stockholders’ equity. If any adjustment to

fair value reflects a significant decline in the value of the security, we evaluate the extent to which the decline is determined to be other-than-temporary and would mark the security to market through a charge to our consolidated statements of operations and comprehensive loss. Credit losses are identified when we do not expect to receive cash flows sufficient to recover the amortized cost basis of a security. In the event of a credit loss, only the amount associated with the credit loss is recognized in operating results, with the amount of loss relating to other factors recorded in accumulated other comprehensive gain (loss).

Property and Equipment

—Property and equipment are recorded at cost and consist of computer and other equipment, capitalized software, furniture and fixtures and leasehold improvements. Depreciation is calculated using the straight-line method over the estimated useful lives of the assets, or for leasehold improvements, over the remaining term of the lease, if shorter. The estimated useful life for each major asset classification are as follows:


Asset Classification		Estimated Useful Life
Computer and other equipment		3 years
Capitalized software		3 years
Furniture and fixtures		6 years
Leasehold improvements		lesser of lease life or useful life

Maintenance and repairs which do not extend the lives of the assets are charged directly to expense as incurred. Upon retirement or disposal, cost and related accumulated depreciation are removed from the related accounts, and any resulting gain or loss is recognized as a component of income or loss in the consolidated statements of operations and comprehensive loss.

Impairment of Long-Lived Assets

—When indications of potential impairments are present, the Company evaluates the carrying value of long-lived assets. The Company adjusts the carrying value of the long-lived assets if the sum of undiscounted expected future cash flows is less than the carrying value. No such impairments were recorded during the years ended December 31, 2025 or 2024.

Leases

—At the inception of an arrangement, we determine if an arrangement is, or contains, a lease based on the facts and circumstances present in that arrangement. Lease classification, recognition, and measurement are then determined at the lease commencement date. For arrangements that contain a lease we (i) identify lease and

non-lease

components, (ii) determine the consideration in the contract, (iii) determine whether the lease is an operating or financing lease; and iv) recognize lease

right-of-use

(“ROU”) assets and liabilities. Lease liabilities and their corresponding ROU assets are recorded based on the present value of fixed, or in substance fixed, lease payments over the expected lease term. When the interest rate implicit in lease contracts is not readily determinable we use our incremental borrowing rate based on the information available at the lease commencement date, which represents an internally developed rate that would be incurred to borrow, on a collateralized basis, over a similar term, an amount equal to the lease payments in a similar economic environment.

We have elected to combine lease components with

non-lease

components on our office real estate asset class. Fixed, or in substance fixed, lease payments on operating leases are recognized over the expected term of the lease on a straight-line basis. Variable lease expenses that are not considered fixed, or in substance fixed, are recognized as incurred. Fixed and variable lease expense on operating leases is recognized within operating expenses within our consolidated statements of operations and comprehensive loss. Some leases include options to extend or terminate the lease and the Company includes these options in the recognition of the Company’s ROU assets and lease liabilities when it is reasonably certain that the Company will exercise such options. We have elected the short-term lease exemption and, therefore, do not recognize a ROU asset or corresponding liability for lease arrangements with an original term of 12 months or less.

Income Taxes

—The Company uses the asset and liability method of accounting for income taxes, as set forth in ASC 740,

Accounting for Income Taxes

(“ASC 740”). Under this method, deferred tax assets and liabilities are recognized for the expected future tax consequence of temporary differences between the carrying amounts and the

tax basis of assets and liabilities and net operating loss carry forwards, all calculated using presently enacted tax rates for the years and jurisdictions in which the temporary differences are expected to be recovered. Changes in deferred tax assets and liabilities are recorded in the provision for income taxes.

The Company evaluates whether deferred tax assets are more likely than not of being realized in determining whether a valuation allowance is necessary. In making such a determination, the Company considers all available positive and negative evidence, including the future reversals of existing taxable temporary differences, projected future taxable income exclusive of reversing temporary differences and carryforwards,

tax-planning

strategies, taxable income in prior carryback years if permitted under tax law, and the results from prior years. If the Company determines it is more likely than not, that all or a portion of a deferred tax asset will not be realized a valuation allowance is recorded with a charge to income tax expense. Alternatively, if the Company determines that all or a portion of a deferred tax asset previously not meeting the more likely than not threshold will be realized, the Company reduces its valuation allowance and recognizes a benefit in income tax expense. As of December 31, 2025 and 2024, the Company determined that it is more likely than not that deferred taxes will not be realized and as a result recorded a full valuation allowance against its deferred tax assets.

The Company files a consolidated U.S. federal income tax return and has elected to include all subsidiaries owned more than 80%.

The Company recognizes and measure uncertain tax benefits in accordance with ASC 740 based on a

two-step

process in which (1) the Company determines whether it is more likely than not that the tax position will be sustained based on the technical merits of the position, and (2) for those tax positions that meet the

more-likely-than-not

recognition threshold, the Company recognizes the largest amount of tax benefit that is more than fifty percent likely to be realized upon ultimate settlement with the related tax authority. The Company’s policy is to recognize interest and penalties related to uncertain tax positions, if any, in income tax expense.

Research and Development Expenses

—Research and development expenses are comprised of costs incurred in performing research and development activities including personnel salaries, benefits, and share-based compensation; external research and development expenses incurred under arrangements with third parties, such as contract research organization agreements, investigational sites, and consultants; the cost of developing and manufacturing clinical study materials, program regulatory costs, expenses associated with obligations under asset acquisitions, license agreements and other direct and indirect costs. Costs incurred in connection with research and development activities are expensed as incurred. Costs are considered incurred based on an evaluation of the progress to completion of each contract using information and data provided by the respective vendors, including the Company’s clinical sites. Depending upon the timing of invoicing by the service providers, the Company recognizes prepaid expenses or accrued expenses related to these costs. These prepaid expenses or accrued expenses are based on management’s estimates of the work performed under service agreements, milestones achieved, and experience with similar contracts. The Company monitors each of these factors and adjusts estimates accordingly.

Stock Warrants

—The Company accounts for stock warrants as either equity-classified or liability-classified instruments based on an assessment of the warrant’s specific terms and applicable authoritative guidance included in ASC 480,

Distinguishing Liabilities from Equity

(“ASC 480”) and ASC 815,

Derivatives and Hedging

(“ASC 815”). The assessment considers whether the warrants are freestanding financial instruments pursuant to ASC 480, whether the warrants meet the definition of a liability pursuant to ASC 480, and whether the warrants meet all of the requirements for equity classification under ASC 815. This assessment, which requires the use of professional judgment, is conducted at the time of warrant issuance and as of each subsequent quarterly period end date while the warrants are outstanding. Warrants that meet all of the criteria for equity classification are required to be recorded as a component of additional

paid-in

capital at the time of issuance. For issued or modified warrants that do not meet all the criteria for equity classification, the warrants are required to be recorded at their initial fair value on the date of issuance and remeasured each balance sheet date thereafter.

Share-Based Compensation

—The Company accounts for share-based compensation in accordance with ASC 718,

Compensation—Stock Compensation

(“ASC 718”). Generally, share-based compensation is measured at the grant date for all equity-based awards made to employees based on the fair value of the awards and is recognized over the requisite service period, which is generally the vesting period. Share-based compensation for awards with performance conditions are recognized over the service period when achievement of the performance condition is probable. The Company has elected to recognize the actual forfeitures by reducing the share-based compensation in the same period as the forfeitures occur. The Company classifies share-based compensation in its consolidated statements of operations and comprehensive loss in the same manner in which the award recipients’ payroll costs are classified.

The Company estimates the fair value of options granted using the Black-Scholes option pricing model (“Black-Scholes”) for stock option grants. The fair value of the Company’s common stock is used to determine the fair value of restricted stock awards. Black-Scholes requires inputs based on certain subjective assumptions, including the expected stock price volatility, the expected term of the award, the risk-free interest rate and expected dividends. Due to the lack of a public market for the Company’s common stock and lack of company-specific historical and implied volatility data, the Company has based its computation of expected volatility on the historical volatility of a representative group of public companies with similar characteristics to the Company and in 2024, the Company began to include its historical volatility rate in the computation. The historical volatility is calculated based on a period of time corresponding with expected term assumption. The Company uses the simplified method to calculate the expected term for options granted where the expected term equals the arithmetic average of the vesting term and the original contractual term of the options due to its lack of sufficient historical data. The risk-free interest rate is based on U.S. Treasury securities with a maturity date corresponding with the expected term of the associated award. The expected dividend yield is assumed to be zero as the Company has never paid dividends and has no current plans to pay any dividends on its common stock.

Fair Value Measurements

—ASC Topic 820,

Fair Value Measurement

(“ASC 820”), establishes a fair value hierarchy for instruments measured at fair value that distinguishes between assumptions based on market data (observable inputs) and the Company’s own assumptions (unobservable inputs). Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the assets or liabilities and are developed based on the best information available in the circumstances. ASC 820 identifies fair value as the price that would be received to sell an asset or paid to transfer a liability, in an orderly transaction between market participants at the measurement date. As a basis for considering market participant assumptions in fair value measurements, ASC 820 establishes a three-tiered value hierarchy that distinguishes between the following:

Level 1—Quoted market prices in active markets for identical assets or liabilities.

Level 2—Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves.

Level 3—Unobservable inputs for the asset or liability (i.e., supported by little or no market activity). Level 3 inputs include management’s own assumptions about the assumptions that market participants would use in pricing the asset or liability (including assumptions about risk).

To the extent the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair values requires more judgement. Accordingly, the degree of judgement exercised by the Company in determining fair value is greatest for instruments categorized as Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement.

In determining fair value, the Company utilizes valuation techniques that maximize the use of observable inputs and minimize the use of unobservable inputs to the extent possible, as well as considers counterparty credit risk in its assessment of fair value.

Segment Information

—Operating segments are defined as components of an enterprise for which discrete financial information is regularly reviewed by the chief operating decision maker (“CODM”) in deciding how to allocate resources and in assessing operating performance. The Company manages its operations as a single segment for the purposes of allocating resources, assessing performance, and making operating decisions. All tangible assets of the Company are held in the U.S. See Note 12, “Segments” for additional details.

Basic and Diluted Net Loss Per Share

—The Company calculates basic net loss per share by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration of potential dilutive securities. Basic shares outstanding includes the weighted-average effect of the Company’s

pre-funded

warrants to purchase shares of our common stock requiring little consideration upon exercise. Unvested restricted common shares as of December 31, 2025 and 2024 are not considered participating securities and as such are excluded from the weighted-average number of shares used for calculating basic and diluted net loss per share. Diluted net loss per share is computed by dividing the net loss by the sum of the weighted-average number of common shares outstanding during the period plus the dilutive effects of potentially dilutive securities outstanding during the period. Potentially dilutive securities include restricted common shares and stock options. The Company has generated a net loss for all periods presented, therefore diluted net loss per share is the same as basic net loss per share since the inclusion of potentially dilutive securities would be anti-dilutive.

Revenue Recognition

—The Company recognizes revenue in accordance with the provisions of ASC Topic 606,

Revenue from Contracts with Customers

(“ASC 606”). The Company recognizes revenue when the Company’s customer obtains control of promised goods or services, in an amount that reflects the consideration which the Company expects to receive in exchange for those goods and services. To determine revenue recognition for arrangements within the scope of ASC 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when or as the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration to which it is entitled in exchange for the goods or services it transfers to the customer.

The Company evaluates the promised goods or services in these agreements to determine which ones represent distinct performance obligations. These agreements may include the following types of promised goods or services: (i) grants of licenses and related transfer of

know-how,

(ii) performance of research and development services, and (iii) participation on joint research and/or development committees. They also may include options to obtain further research and development services and licenses to the Company’s intellectual property. The payment terms of these agreements may include nonrefundable upfront fees, payments based upon the achievement of certain milestones, and additional payments based on product sales derived from the collaboration.

The Company exercises judgment in assessing those promised goods and services that are distinct and thus representative of performance obligations. To the extent the Company identifies multiple performance obligations in a contract or group of contracts signed together, the Company must develop assumptions that require judgment to determine the estimated standalone selling price for each performance obligation in order to allocate the transaction price among the identified performance obligations. The transaction is allocated on a relative standalone selling price basis.

Prior to recognizing revenue, the Company makes estimates of the transaction price, including variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved. These estimates are reassessed at each reporting period as required.

The Company then recognizes revenue in the amount of the transaction price that is allocated to the respective performance obligations when or as the performance obligations are satisfied. For performance obligations satisfied over time, the Company estimates the efforts needed to complete the performance obligations and recognizes revenue over the satisfaction of the performance obligations.

Restructuring

—The Company accounts for restructuring charges in accordance with ASC Subtopic

420-10,

Exit or Disposal Cost Obligations

. The charges related to the workforce reductions are cash-based expenditures related primarily to severance and benefit payments, with such amounts reflected in the Company’s consolidated statements of operations and other comprehensive loss. See Note 13, “Restructuring” for additional details.

STOCKHOLDERS' EQUITY (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Equity [Abstract]

Summary of Share-based Compensation

Share-based Compensation

Share-based compensation is comprised of the Company’s stock options, restricted stock awards, restricted stock units and shares issued pursuant to the employee stock purchase plan, and is classified in the condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2026 and 2025 was as follows:


	FOR THE THREE MONTHS ENDED MARCH 31,
(in thousands)	2026		2025
Research and development	$	184	$	810
General and administrative		429		1,069

	$	613	$	1,879

Share-based compensation is comprised of the Company’s stock options, restricted stock awards, restricted stock units and shares issued pursuant to the employee stock purchase plan, and is classified in the consolidated statements of operations and comprehensive loss for the years ended December 31, 2025 and 2024 and was as follows:


	FOR THE YEAR ENDED DECEMBER 31,
(in thousands)	2025		2024
Research and development	$	2,250	$	3,269
General and administrative		3,064		4,724

	$	5,314	$	7,993

Summary of Stock Option Activity

The following table summarizes stock option activity for the three months ended March 31, 2026:


Stock Options	Number of Option Shares			Weighted- Average Exercise Price		Weighted- Average Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding stock options at December 31, 2025		628,280		$	43.42		7.6	$	89
Granted		32,360		$	4.45
Forfeited		(11,404	)	$	15.70
Expired		(1,281	)	$	88.75
Exercised		(561	)	$	6.08

Outstanding stock options at March 31, 2026		647,394		$	41.90		6.2	$	749

Exercisable stock options at March 31, 2026		427,642		$	56.52		5.6	$	180

The following table summarizes stock option activity for the year ended December 31, 2025:


Stock Options	Number of Option Shares			Weighted- Average Exercise Price		Weighted- Average Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding stock options at December 31, 2024		529,342		$	62.83		7.8	$	—
Granted		224,179		$	5.87
Forfeited		(51,758	)	$	32.54
Expired		(73,483	)	$	76.34
Exercised		—		$	—

Outstanding at December 31, 2025		628,280		$	43.42		7.6	$	89

Exercisable stock options at December 31, 2025		399,047		$	58.72		7.1	$	—

Summary of Assumptions of Fair Value of Option Pricing Granted

The fair value of the stock options granted during the three months ended March 31, 2026 and 2025 was determined using the Black-Scholes option pricing model with the following assumptions:


	FOR THE THREE MONTHS ENDED MARCH 31,
	2026		2025
Expected volatility		109.21%		91.88%–119.61%
Expected term (years)		5.25		5.27–6.02
Risk free interest rate		3.68%		4.36%–4.39%
Expected dividend yield		—		—
Exercise price	$	4.45	$	6.08–$7.60

The fair value of the stock options granted during the years ended December 31, 2025 and 2024 was determined using the Black-Scholes option pricing model with the following assumptions:


	FOR THE YEAR ENDED DECEMBER 31,
	2025		2024
Expected volatility		91.88% - 119.61%		89.41% - 94.48%
Expected term (years)		5.27 - 6.02		5.50 - 6.02
Risk free interest rate		4.03 % - 4.39%		3.93% - 4.35%
Expected dividend yield		—		—
Exercise price	$	2.38 - $7.60	$	14.88 - $19.20

Summary of Unvested Restricted Common Stock Awards

A summary of the status of the Company’s nonvested restricted common stock awards at December 31, 2025 and changes during the year ended December 31, 2025 was as follows:


Restricted Stock Awards	Shares			Weighted- Average Grant Date Fair Value Per Share
Nonvested restricted common stock awards at December 31, 2024		2,687		$	31.76
Granted		—		$	—
Vested		(2,687	)	$	31.76
Forfeited		—		$	—

Nonvested restricted common stock awards at December 31, 2025		—		$	—

Summary of Unvested Restricted Common Stock Units

A summary of the status of the Company’s nonvested restricted common stock units at March 31, 2026 and changes during the three months ended March 31, 2026 was as follows:


Restricted Stock Units	Shares			Weighted- Average Grant Date Fair Value Per Share
Nonvested restricted stock units at December 31, 2025		38,603		$	9.60
Granted		5,000		$	4.45
Forfeited		(4,150	)	$	2.40
Vested		(6,354	)	$	7.79

Nonvested restricted stock units at March 31, 2026		33,099		$	10.07

A summary of the status of the Company’s nonvested restricted common stock units at December 31, 2025 and changes during the year ended December 31, 2025 was as follows:


Restricted Stock Units	Shares			Weighted- Average Grant Date Fair Value Per Share
Nonvested restricted common stock units at December 31, 2024		133,069		$	18.89
Granted		59,500		$	5.96
Forfeited		(66,646	)	$	12.34
Vested		(87,320	)	$	19.18

Nonvested restricted common stock units at December 31, 2025		38,603		$	9.60

BALANCE SHEET COMPONENTS - Schedule Of Accrued Expenses (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Balance Sheet Related Disclosures [Abstract]
Compensation and related expenses	$ 1,407	$ 2,334	$ 3,095
Professional fees	1,396	1,039	510
Research and development	94	394	1,197
Other	204	24	160
Accrued expenses	$ 3,101	$ 3,791	$ 4,962

BUSINESS AND LIQUIDITY - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	May 04, 2026	Mar. 01, 2026	Mar. 31, 2026	Feb. 06, 2026	Jan. 26, 2026	Dec. 31, 2025	Dec. 31, 2024	Apr. 30, 2024
Business Disclosure [Line Items]
Cash, cash equivalents and marketable securities			$ 46.8			$ 54.7
Common stock, par value (in dollars per share)			$ 0.0001			$ 0.0001	$ 0.0001	$ 0.0001
Subsequent Event [Member]
Business Disclosure [Line Items]
Common stock, par value (in dollars per share)		$ 0.0001		$ 0.0001	$ 0.0001
Merger And Reorganization Concurrent Financing		$ 505.5
Merger And Reorganization Cash And Cash Equivalents At Carrying Value		37.5
Subsequent Event [Member] \| Purchase Commitment [Member]
Business Disclosure [Line Items]
Concurrent financing		$ 505.5
Subsequent Event [Member] \| Pre-Merger Equityholders of Candid [Member]
Business Disclosure [Line Items]
Merger And Reorganization Combined Ownership Percentage		57.55%
Merger And Reorganization Consideration Transferred Expected Value		$ 750.0
Subsequent Event [Member] \| Pre-Merger Equityholders of Candid [Member] \| Concurrent Financing [Member]
Business Disclosure [Line Items]
Merger And Reorganization Combined Ownership Percentage		38.80%
Subsequent Event [Member] \| Pre-Merger Equityholders of Rallybio [Member]
Business Disclosure [Line Items]
Merger And Reorganization Consideration Transferred Expected Value		$ 47.5
Subsequent Event [Member] \| Pre-Merger Equityholders of Rallybio [Member] \| Candid [Member]
Business Disclosure [Line Items]
Merger And Reorganization Combined Ownership Percentage		3.65%	3.65%
Subsequent Event [Member] \| Merger Agreement [Member]
Business Disclosure [Line Items]
Business Combination, Pro Forma Information, Description		pre-Merger equityholders of Candid (other than investors in the Concurrent Financing) are expected to own approximately 57.55% of the combined company, pre-Merger equityholders of Rallybio are expected to own approximately 3.65% of the combined company and the Investors in the Concurrent Financing are expected to own approximately 38.80% of the combined company (assuming proceeds from the Concurrent Financing of $505.5 million), in each case, calculated on a fully diluted basis, using the treasury stock method, and subject to certain assumptions, including (i) a valuation for Rallybio of $47.5 million (assuming Rallybio has net cash (“Rallybio Net Cash”) of $37.5 million as of the closing of the Merger (the “Closing” and such date, the “Closing Date”)), (ii) a fixed valuation for Candid of $750.0 million, and (iii) the relative capitalization of Rallybio and Candid.
Subsequent Event [Member] \| Rally bio [Member]
Business Disclosure [Line Items]
Business combination termination fee received	$ 50.0
Reimbursement of transaction costs	$ 0.4

MARKETABLE SECURITIES - Schedule of Fair Values of Available-For-Sale Debt Securities By Contractual Maturity (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Investments, Debt and Equity Securities [Abstract]
Due in one year or less	$ 21,879	$ 30,555	$ 51,357
Due after one year through two years	0	0	8,956
Total available-for-sale debt securities by contractual maturity	$ 21,879	$ 30,555	$ 60,313

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION - Additional Information (Details) $ / shares in Units, $ in Thousands		3 Months Ended		12 Months Ended
	Feb. 06, 2026 $ / shares	Mar. 31, 2026 USD ($) $ / shares	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($) $ / shares	Dec. 31, 2024 USD ($) $ / shares	Mar. 01, 2026 $ / shares	Jan. 26, 2026 $ / shares	Apr. 30, 2024 $ / shares
Disclosure Significant Accounting Policies [Line Items]
Net loss		$ 8,278	$ 9,439	$ 8,978	$ 57,775
Retained earnings (accumulated deficit)		310,276		301,998	293,020
Cash, cash equivalents and marketable securities		$ 46,800		54,700
Impairments				$ 0	$ 0
Subsidiaries, ownership percentage				80.00%
Common stock, par value (in dollars per share) \| $ / shares		$ 0.0001		$ 0.0001	$ 0.0001			$ 0.0001
Gain on sale of joint venture				$ 23,000
Future contingent milestone and royalty assets		$ 3,000		$ 3,000
Subsequent Event [Member]
Disclosure Significant Accounting Policies [Line Items]
Common stock, par value (in dollars per share) \| $ / shares	$ 0.0001					$ 0.0001	$ 0.0001
Ratio of record date	1.08

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION - Summary of Property and Equipment Estimated Useful Lives (Details)	Dec. 31, 2025
Computer and other equipment
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives	3 years
Capitalized software
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives	3 years
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Property and equipment, estimated useful lives	6 years

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Cash Flows Used in Operating Activities:
Net loss	$ (8,278)	$ (9,439)	$ (8,978)	$ (57,775)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3	28	92	131
Net accretion of discounts/premiums on debt securities	(51)	(210)	(573)	(1,612)
Share-based compensation	613	1,879	5,314	7,993
Gain on sale of joint venture			(22,350)	0
Loss on investment in joint venture	0	587	874	2,239
Changes in operating assets and liabilities:
Prepaid expenses, operating right-of-use assets and other current assets	(155)	(506)	(2,043)	2,724
Accounts payable	814	122	(152)	(698)
Accrued expenses and operating lease liabilities	(712)	(2,454)	(1,149)	(3,344)
Deferred revenue	(212)	(212)	(848)	1,060
Net cash used in operating activities	(7,978)	(10,205)	(29,813)	(49,282)
Cash Flows Provided by Investing Activities:
Purchases of marketable securities	0	(5,919)	(17,697)	(48,933)
Proceeds from maturities of marketable securities	17,900	18,000	46,465	84,425
Proceeds from sale of common stock received from sale of joint venture			20,000	0
Investment in joint venture	0	(1,000)	(1,500)	(2,000)
Net cash provided by investing activities	17,900	11,081	47,268	33,492
Cash Flows Provided by Financing Activities:
Proceeds from the issuance of common stock from a securities purchase agreement	3	0	0	5,405
Proceeds from the issuance of common stock under the stock purchase plan			16	62
Payments of offering costs			0	(268)
Net cash provided by financing activities	3	0	16	5,199
Net increase (decrease) in cash and cash equivalents	9,925	876	17,471	(10,591)
Cash and cash equivalents—beginning of year	31,374	13,903	13,903	24,494
Cash and cash equivalents—end of year	$ 41,299	$ 14,779	$ 31,374	$ 13,903

NET LOSS PER COMMON SHARE (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Earnings Per Share [Abstract]

Summary of Basic and Diluted Loss Per Common Share

Basic and diluted net loss per common share for the three months ended March 31, 2026 and 2025 was calculated as follows:


	FOR THE THREE MONTHS ENDED MARCH 31,
(in thousands except share and per share amounts)	2026			2025
Net loss	$	(8,278	)	$	(9,439	)
Weighted-average number of common shares outstanding, basic and diluted		5,688,584			5,597,528
Net loss per common share, basic and diluted	$	(1.46	)	$	(1.69	)

Basic and diluted loss per common share were calculated as follows:


	FOR THE YEAR ENDED DECEMBER 31,
(in thousands except share and per share amounts)	2025			2024
Net loss	$	(8,978	)	$	(57,775	)
Weighted-average number of common shares outstanding, basic and diluted		5,629,370			5,443,332

Net loss per common share, basic and diluted	$	(1.59	)	$	(10.61	)

MARKETABLE SECURITIES - Additional Information (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Aggregate fair value of available-for-sale debt securities in an unrealized loss position	$ 0.0	$ 0.7	$ 10.4
Continuous unrealized loss position for more than twelve months	0.0	0.0	0.0
Allowance for credit losses	$ 0.0	$ 0.0	$ 0.0

- Definition

Amount of allowance for credit loss on financing receivable. Excludes allowance for financing receivable covered under loss sharing agreement.

+ References + Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

LEASES - Schedule of Assets And Liabilities, Lessee (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Assets:
Operating lease right-of-use assets	$ 152	$ 175	$ 152
Liabilities:
Operating lease liabilities	99	94	154
Operating lease liabilities, noncurrent	$ 55	82	0
Total operating lease liabilities		$ 176	$ 154

LEASES (Tables)

12 Months Ended

Dec. 31, 2025

Leases [Abstract]

Schedule of Assets And Liabilities, Lessee

The following table summarizes the presentation of the Company’s operating lease as presented on the consolidated balance sheets:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Assets:
Operating lease right-of-use assets	$	175	$	152

Liabilities:
Operating lease liabilities	$	94	$	154
Operating lease liabilities, noncurrent		82		—

Total operating lease liabilities	$	176	$	154

Schedule of Future Minimum Annual Lease Payments

Future minimum lease payments from December 31, 2025 until the expiration of the operating lease are as follows:


(in thousands)
2026	$	106
2027		84
Thereafter		—

Total lease payments		190
Less: imputed discount rate		(14	)

Carrying value of operating lease liabilities	$	176

SEGMENTS (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
SEGMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Segment Reporting Information [Line Items]
Revenue	$ 212	$ 212	$ 858	$ 636
Research and development	2,871	5,725	19,597	41,507
Segment net loss	(8,278)	(9,439)	$ (8,978)	(57,775)
Number Of Reportable Segments Not Disclosed Flag			true
Reporting Segment
Segment Reporting Information [Line Items]
Revenue	212	212	$ 858	636
General and administrative, excluding personnel expenses	4,223	1,525	6,078	6,654
General and administrative, personnel expenses (including share-based compensation)	1,851	2,632	8,247	12,971
Other segment items	(455)	(231)	(24,086)	(2,721)
Segment net loss	(8,278)	(9,439)	(8,978)	(57,775)
RLYB212 \| Reporting Segment
Segment Reporting Information [Line Items]
Research and development	56	2,438	6,291	21,287
RLYB116 \| Reporting Segment
Segment Reporting Information [Line Items]
Research and development	396	619	3,786	4,841
Other program candidates \| Reporting Segment
Segment Reporting Information [Line Items]
Research and development	2	(163)	(29)	1,901
Personnel (including share-based compensation) \| Reporting Segment
Segment Reporting Information [Line Items]
Research and development	2,280	2,589	8,798	12,488
Other \| Reporting Segment
Segment Reporting Information [Line Items]
Research and development	$ 137	$ 242	$ 751	$ 990

SUBSEQUENT EVENTS - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	May 04, 2026	Aug. 26, 2025	Feb. 24, 2025	Mar. 31, 2026	Mar. 01, 2026	Feb. 06, 2026	Jan. 26, 2026	Dec. 31, 2025	Dec. 31, 2024	Apr. 30, 2024
Subsequent Event [Line Items]
Minimum bid price per share threshold			$ 1
Common stock, par value (in dollars per share)				$ 0.0001				$ 0.0001	$ 0.0001	$ 0.0001
Thres hold number of consecutive business days			30 days
Stock listing exchange minimum bid price compliance extension period		180 days
Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock, par value (in dollars per share)					$ 0.0001	$ 0.0001	$ 0.0001
Merger and reorganization concurrent financing					$ 505.5
Merger and reorganization cash and cash equivalents at carrying value					$ 37.5
Subsequent Event [Member] \| PreMerger Equityholders of Candid [Member]
Subsequent Event [Line Items]
Merger and reorganization combined ownership percentage					57.55%
Merger and reorganization consideration transferred expected value					$ 750.0
Subsequent Event [Member] \| PreMerger Equityholders of Rallybio [Member]
Subsequent Event [Line Items]
Merger and reorganization consideration transferred expected value					$ 47.5
Subsequent Event [Member] \| Candid [Member] \| PreMerger Equityholders of Rallybio [Member]
Subsequent Event [Line Items]
Merger and reorganization combined ownership percentage				3.65%	3.65%
Subsequent Event [Member] \| Concurrent Financing [Member] \| PreMerger Equityholders of Candid [Member]
Subsequent Event [Line Items]
Merger and reorganization combined ownership percentage					38.80%
Subsequent Event [Member] \| Rally bio [Member]
Subsequent Event [Line Items]
Business combination termination fee received	$ 50.0
Reimbursement of transaction costs	$ 0.4

INCOME TAXES

12 Months Ended

Dec. 31, 2025

Income Tax Disclosure [Abstract]

INCOME TAXES

8. INCOME TAXES

The following table summarizes income (loss) before income taxes:


(in thousands)	2025
Domestic	$	(8,978	)
Foreign		—

Total	$	(8,978	)

The Company had no income tax expense (benefit) as of December 31, 2025 and 2024.

The Company’s effective tax rate for the period ended December 31, 2025 was 0.0%. For the period ended December 31, 2025, the primary drivers of the variance from the statutory rate were state taxes, research & development tax credits, stock based compensation, and valuation allowance.

The following is a reconciliation from the Company’s statutory rate to the effective tax rate reported in the financial statements:


	2025
(in thousands)	Amount			Rate
Statutory federal income tax rate	$	(1,885	)		21.0	%
Tax credits (federal):
Orphan drug credit		(1,331	)		14.8	%
Other		(231	)		2.6	%
Valuation allowance		2,203			(24.5	%)
Non-deductible or non-taxable items:
Share-based compensation		1,227			(13.7	)%
Other adjustments		17			(0.2	%)

Effective income tax rate	$	—			0.0	%

The Company’s effective income tax rates are different from the federal statutory tax rates in 2024 predominantly due to the valuation allowance, tax credits, and state taxes. A reconciliation of the effect of applying the federal statutory rate to the net loss and effective income tax rate are as follows:


	2024
U.S. federal statutory income tax rate		21.0	%
State income taxes, net of federal income tax benefit		5.4	%
Tax credits		10.7	%
Other		(2.9	)%
Valuation allowance		(34.2	)%

Effective income tax rate		—	%

The tax effect of temporary differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases that give rise to deferred tax assets and liabilities are as follows at December 31, 2025 and 2024:


(in thousands)	2025			2024
Net operating loss carryforwards	$	50,322		$	45,973
Amortization		1,775			1,341
Section 174 capitalization		19,947			22,479
Research and development tax credits		25,701			24,047
Share-based compensation		2,405			2,654
Other		301			1,476

Total deferred tax assets		100,451			97,970
Valuation allowance		(100,451	)		(97,970	)

Net deferred tax assets	$	—		$	—

As of December 31, 2025, the Company’s federal and state post-apportioned carryforwards are approximately $183.3 million and $181.6 million, respectively. Of the federal amount, $183.3 million will have an indefinite carryforward period. Of the state post-apportioned amount, $181.6 million have a limited carryforward period and will begin to expire in 2038.

As of December 31, 2025, the Company’s federal and state carryforwards are approximately $25.0 million and $0.9 million, respectively. All tax credits have a limited carryforward period and will begin to expire in 2038.

After weighing all available positive and negative evidence, the Company has recorded a valuation allowance of approximately $100.5 million and $98.0 million as of December 31, 2025 and 2024, respectively. The Company increased the valuation allowance by $2.5 million and $19.7 million for the years ended December 31, 2025 and 2024, respectively.

The Company is subject to income tax in multiple jurisdictions, including federal, states, and city jurisdictions. The Company has federal, state, and city income tax returns that are open to examination from 2022, 2023, and 2024 forward, respectively. In addition, the utilization of tax carryforwards, from periods prior to those previously mentioned may also be audited by the taxing authorities once utilized.

As a result, the Company continuously monitors its current and prior filing positions in order to determine if any unrecognized tax positions need to be recorded. The analysis involves considerable judgement and is based on the best information available. As of December 31, 2025 the Company has no unrecognized tax benefits.

The Company has

not

accrued any interest expense or penalties related to the unrecognized tax benefits for the period ended December 31, 2025.

The Company has made no income tax payments and received no income tax refunds during the periods ended December 31, 2025 and 2024. All payments made to taxing authorities were for

non-income

based tax liabilities and are outside the scope of ASC 740.

The One Big Beautiful Bill Act (the “OBBBA”) was enacted on July 4, 2025. The Company has evaluated whether the OBBBA has a material impact on its 2025 financial statements. The only provision of the OBBBA that impacts the Company’s income tax accounting under Accounting Standards Codification 740 is the new Internal Revenue Code of 1986, as amended, Section 174A (“Section 174A”), which permanently allows taxpayers to fully expense domestic research or experimental (“R&E”) expenditures paid or incurred in taxable years beginning after December 31, 2024. The requirement to capitalize foreign expenses under Internal Revenue Code Section 174 over 15 years has not changed. On August 28, 2025, the Internal Revenue Service released procedural guidance (Rev. Proc.

20;/.25-28)

for implementing Section 174A and related elections for domestic R&E. Transition rules provide taxpayers with options to account for any remaining unamortized domestic R&E expenditures paid or incurred in taxable years beginning after December 31, 2021, and before January 1, 2025. Taxpayers may continue to amortize such unamortized amounts over the remaining five-year period; alternatively, they may elect to deduct any remaining unamortized domestic R&E expenditures either entirely in the first tax year beginning after December 31, 2024, or ratably over two taxable years (e.g., 2025 or ratably in 2025 and 2026). The company has decided it will elect to continue to amortize previously capitalized and unamortized domestic R&E expenditures over the remaining five-year period. As of December 31, 2024, the company had approximately $41.4 million of remaining unamortized domestic research and development expenditures, representing approximately $11.4 million of its gross deferred tax assets. As of December 31, 2025, the company had approximately $25.5 million of remaining unamortized domestic research and development expenditures, representing approximately $7.0 million of its gross deferred tax assets.

Utilization of the U.S. federal and state net operating loss carryforwards and research and development tax credit carryforwards may be subject to an annual limitation under Section 382 and Section 383 of the Code, and corresponding provisions of state law, due to ownership changes that may have occurred previously or that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income and tax liabilities. In general, an ownership change, as defined by Section 382 of the Code, results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 5% over a three-year period.

The Company completed a Section 382 study and concluded that it underwent an ownership change as defined by the Code during the year ended December 31, 2021. The Company does not currently believe that the annual limitation will result in the expiration of any net operating losses or research and development tax credit carryforwards before utilization. Additional ownership changes which may have occurred after December 31, 2021 and any future ownership changes may limit our ability to utilize remaining tax attributes. Any carryforwards that will expire prior to utilization as a result of such additional limitations will be removed from deferred tax assets, with a corresponding reduction of the valuation allowance. Due to the existence of the valuation allowance, limitations created by future ownership changes, if any, will not impact the Company’s effective tax rate.

ASC 740 addresses the determination of whether tax benefits claimed or expected to be claimed on a tax return should be recorded in the financial statements. Under ASC 740, the Company may recognize the tax benefit from an uncertain tax position only if it is more likely that not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The Company has no material uncertain tax positions that qualify for either recognition or disclosure in consolidated financial statements.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477617/942-740-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478822/944-740-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12C

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12B

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477891/740-270-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-13

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/740/tableOfContent

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-14

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-21

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-17

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

+ Details

MARKETABLE SECURITIES - Schedule of Marketable Securities by Balance Sheet Location Classification (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Debt securities, available-for-sale	$ 21,879	$ 30,555	$ 60,313
Cash and cash equivalents
Debt Securities, Available-for-Sale [Line Items]
Debt securities, available-for-sale	16,383	7,193	8,705
Marketable securities
Debt Securities, Available-for-Sale [Line Items]
Debt securities, available-for-sale	$ 5,496	$ 23,362	$ 51,608

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (bbb)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-SubTopic 10
-Topic 825
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482881/825-10-55-10

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482736/825-10-45-1A

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-11

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-10

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482881/825-10-55-12

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 103
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-103

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 100
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482078/820-10-55-100

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482106/820-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 14: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481830/320-10-45-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

RESTRUCTURING AND SEVERANCE - Schedule of Restructuring and Related Costs (Details) - Employee Severance - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Restructuring Reserve [Roll Forward]
Beginning accrued severance	$ 523	$ 203
Severance incurred during the period	2,302	1,706
Severance paid and adjustments made during the period	(1,449)	(1,386)
Ending accrued severance	$ 1,376	$ 523
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]		Operating Expenses

- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References + Details

STOCKHOLDERS' EQUITY - Summary of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Number of Option Shares
Outstanding at beginning of period (in shares)	628,280	529,342	529,342
Granted (in shares)	32,360		224,179
Forfeited (in shares)	(11,404)		(51,758)
Expired (in shares)	(1,281)		(73,483)
Exercised (in shares)	(561)		0
Outstanding at ending of period (in shares)	647,394		628,280	529,342
Options exercisable at ending of period (in shares)	427,642		399,047
Weighted-Average Exercise Price
Outstanding at beginning of period (in dollars per share)	$ 43.42	$ 62.83	$ 62.83
Granted (in dollars per share)	4.45		5.87
Forfeited (in dollars per share)	15.7		32.54
Expired (in dollars per share)	88.75		76.34
Exercised (in dollars per share)	6.08		0
Outstanding at ending of period (in dollars per share)	41.9		43.42	$ 62.83
Options exercisable at ending of period (in dollars per share)	$ 56.52		$ 58.72
Weighted-Average Contractual Term (in years) and Aggregate Intrinsic Value (in thousand)
Outstanding, Weighted-Average Contractual Term (in years)	7 years 7 months 6 days	6 years 2 months 12 days	7 years 9 months 18 days	7 years 7 months 6 days
Options exercisable, Outstanding, Weighted-Average Contractual Term (in years)	5 years 7 months 6 days		7 years 1 month 6 days
Outstanding, Aggregate Intrinsic Value	$ 749		$ 89	$ 0
Options exercisable, Aggregate Intrinsic Value	$ 180		$ 0

COMMITMENTS AND CONTINGENCIES	3 Months Ended	12 Months Ended
COMMITMENTS AND CONTINGENCIES	Mar. 31, 2026	Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	7. COMMITMENTS AND CONTINGENCIES Purchase Commitments — The Company enters contracts in the normal course of business with contract research organizations and other third-party vendors for clinical trials and testing and manufacturing services. These contracts generally do not contain minimum purchase commitments and are cancellable by the Company upon written notice. Payments that may be due upon cancellation consist of payments for services provided or expenses incurred prior to cancellation. As of March 31, 2026 and December 31, 2025, there were no amounts accrued related to termination charges.	10. COMMITMENTS AND CONTINGENCIES Purchase Commitments —The Company enters contracts in the normal course of business with contract research organizations (“CROs”) and other third-party vendors for clinical trials and testing and manufacturing services. These contracts generally do not contain minimum purchase commitments and are cancellable by us upon written notice. Payments that may be due upon cancellation consist of payments for services provided or expenses incurred prior to cancellation. As of December 31, 2025 and 2024 there were no amounts accrued related to termination charges.

BALANCE SHEET COMPONENTS - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Property, Plant and Equipment [Line Items]
Total property and equipment		$ 503	$ 769
Less: accumulated depreciation		(480)	(654)
Total property and equipment—net	$ 20	23	115
Computer and other equipment
Property, Plant and Equipment [Line Items]
Total property and equipment		191	191
Capitalized software
Property, Plant and Equipment [Line Items]
Total property and equipment		89	89
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Total property and equipment		76	151
Leasehold improvements
Property, Plant and Equipment [Line Items]
Total property and equipment		$ 147	$ 338

COMMITMENTS AND CONTINGENCIES (Details) - USD ($)	3 Months Ended	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Details) - USD ($)	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Termination charges	$ 0	$ 0	$ 0

STOCKHOLDERS' EQUITY - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended		12 Months Ended
	Jan. 01, 2026	Jan. 01, 2025	Apr. 30, 2024	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2021	Nov. 30, 2022
Class of Stock [Line Items]
Common stock, shares authorized (in shares)				200,000,000		200,000,000	200,000,000
Common stock, shares outstanding (in shares)				5,290,236		5,283,321	5,188,743
Common stock, shares issued (in shares)				5,290,236		5,283,321	5,188,743
Preferred stock, shares authorized (in shares)				50,000,000		50,000,000	50,000,000
Preferred stock, shares outstanding (in shares)				0		0	0
Weighted average grant date fair value (in dollars per share)				$ 3.6	$ 5.36	$ 4.92	$ 11.78
Intrinsic value of stock options vested						$ 0
Unrecognized share-based compensation expense				$ 2,200		$ 2,800
Total unrecognized compensation costs, weighted average period for recognition				1 year 7 months 6 days		1 year 10 months 24 days
Share-based compensation				$ 613	$ 1,879	$ 5,314	$ 7,993
Outstanding, Aggregate Intrinsic Value				749		89	$ 0
Options exercisable, Aggregate Intrinsic Value				$ 180		$ 0
Share Price				$ 8.97		$ 5.49
Restricted Stock Awards
Class of Stock [Line Items]
Unrecognized share-based compensation expense, restricted stock awards						$ 0
Restricted Stock Units (RSUs)
Class of Stock [Line Items]
Total unrecognized compensation costs, weighted average period for recognition				2 years		2 years 4 months 24 days
Unrecognized share-based compensation expense, restricted stock units				$ 200		$ 300
2021 Equity Incentive Plan
Class of Stock [Line Items]
Percentage of number of shares of common stock outstanding								5.00%
Number of shares increased (in shares)	264,166	259,438				259,438	236,434
Shares reserved for future issuance (in shares)				1,514,824		1,257,573		680,043
Shares available for future issuance (in shares)				834,331		590,690
2021 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock issuable (in shares)								36,415
Percentage of number of shares of common stock outstanding						1.00%
Number of shares increased (in shares)		0
Shares available for future issuance (in shares)				94,281		94,281
Common stock shares outstanding (in shares)				72,831		72,831
Shares issued (in shares)						7,258	7,603
Share-based compensation arrangement by share-based payment award, purchase price of common stock, percent				85.00%		85.00%
Share-based compensation						$ 16	$ 100
Follow-on Offering \| Pre-Funded Warrants
Class of Stock [Line Items]
Number of securities called by warrants or rights (in shares)					416,673				416,673
Common stock price per share (in dollars per share)									$ 47.9992
Pre-funded warrants exercise price (in dollars per share)									$ 0.0008
Percent excess limit				9.99%		9.99%
Days of notice				61 days		61 days
Percentage of common stock beneficially owned not exceed				19.99%		19.99%
Securities Purchase Agreement \| Johnson & Johnson
Class of Stock [Line Items]
Sale of stock, number of shares issued in transaction (in shares)			454,545
Sale of stock, price per share (in dollars per share)			$ 14.56
Sale of stock, premium on stock price (as a percent)			10.00%
Gross proceeds			$ 6,600

INCOME TAXES - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Operating Loss Carryforwards [Line Items]
Income tax benefit	$ 0	$ 0
Federal net operating loss carry forwards	183,300,000
State net operating loss carry forwards	181,600,000
Income tax penalties and interest accrued	$ 0
Effective income tax rate reconciliation, percent	0.00%	0.00%
Deferred Tax Assets, Valuation Allowance	$ 100,451,000	$ 97,970,000
Unamortized Domestic Research and Development Expenditures	25,500,000	41,400,000
Unamortized deferred tax assets	7,000,000	11,400,000
Valuation allowance, deferred tax asset, increase amount	2,500,000	19,700,000
Income Taxes Paid	0	0
Proceeds from Income Tax Refunds	$ 0	$ 0
Unamortized Domestic Research And Development Expenditures Term	5 years
Domestic Tax Jurisdiction
Operating Loss Carryforwards [Line Items]
Deferred tax assets, tax credit carryforwards	$ 25,000,000
State and Local Jurisdiction
Operating Loss Carryforwards [Line Items]
Deferred tax assets, tax credit carryforwards	$ 900,000

STOCKHOLDERS' EQUITY - Summary of NonVested Restricted Common Stock Awards (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Restricted Stock Awards
Shares
Outstanding, beginning balance (in shares)	0	2,687
Granted (in shares)		0
Vested (in shares)		(2,687)
Forfeited (in shares)		0
Outstanding, ending balance (in shares)		0
Weighted-Average Grant Date Fair Value Per Share
Outstanding, beginning balance (in dollars per share)	$ 0	$ 31.76
Granted (in dollars per share)		0
Vested (in dollars per share)		31.76
Forfeited (in dollars per share)		0
Outstanding, ending balance (in dollars per share)		$ 0
Restricted Stock Units (RSUs) [Member]
Shares
Outstanding, beginning balance (in shares)	38,603	133,069
Granted (in shares)	5,000	59,500
Vested (in shares)	(6,354)	(87,320)
Forfeited (in shares)	(4,150)	(66,646)
Outstanding, ending balance (in shares)	33,099	38,603
Weighted-Average Grant Date Fair Value Per Share
Outstanding, beginning balance (in dollars per share)	$ 9.6	$ 18.89
Granted (in dollars per share)	4.45	5.96
Vested (in dollars per share)	7.79	19.18
Forfeited (in dollars per share)	2.4	12.34
Outstanding, ending balance (in dollars per share)	$ 10.07	$ 9.6

INVESTMENT IN JOINT VENTURE	3 Months Ended	12 Months Ended
INVESTMENT IN JOINT VENTURE	Mar. 31, 2026	Dec. 31, 2025
Equity Method Investments and Joint Ventures [Abstract]
INVESTMENT IN JOINT VENTURE	6. INVESTMENT IN JOINT VENTURE In July 2025, the Company entered into a Membership Interest Purchase Agreement (the “ENPP1 Purchase Agreement”) to sell its interest in REV102, an ENPP1 inhibitor in preclinical development for the treatment of patients with HPP, to Recursion Exscientia Ventures I, Inc, an indirect wholly-owned subsidiary of Recursion (“Buyer”). In connection with the JV Sale, the Company received compensation in the form of Recursion common stock (which is a non-cash investing activity). The Company subsequently sold the Recursion common stock for cash proceeds of $20.0 million in the third quarter of 2025 which included $7.5 million from an upfront payment and $12.5 million from a milestone payment related to the initiation of additional preclinical studies. The Company is eligible to receive a $5.0 million milestone cash payment in connection with the initiation of dosing in a Phase 1 clinical study, as defined in the ENPP1 Purchase Agreement and low single-digit royalties on all future net sales by Recursion of products comprising or incorporating certain compounds developed by RE Ventures I, LLC, a limited liability company (“REV-I”). The Company may also be eligible to receive certain payments in the event of Recursion’s sale of the REV102 program. The Company evaluated the JV Sale under ASC 860, Transfers and Servicing of Financial Assets (“ASC 860”). Based on the Company’s evaluation of the JV Sale under ASC 860, the Company recognized a gain from the sale of its equity interests in REV102 of $22.4 million, based on the excess of the total net consideration allocated to the sale of the Company’s equity interests (based on relative fair value) of $23.0 million over the carrying value of the equity interests sold of $0.6 million. The total net consideration of $23.0 million included cash received of $20.0 million, plus an estimated $3.0 million representing the fair value of the future milestone payments and future royalties (which is a non-cash investing activity). The contingent consideration was initially measured at fair value using a probability based present value model of the risk-adjusted estimated cash flows, with a discount rate of 15.4%. This valuation model relied on significant unobservable inputs (level 3 inputs) based on management’s estimates, which were informed by external data, judgment, and forecasts. Key assumptions included the probability of achieving the milestone and royalties, timing of cash flows, discount rate, and forecasted net revenues. The fair value of the contingent consideration is a non-recurring fair value measurement and is recorded as other assets and other assets, non-current on the Company’s condensed consolidated balance sheets and as gain on sale of joint venture and other income within the Company’s condensed consolidated statements of operations and comprehensive loss. Prior to the JV Sale, the Company, through one of its wholly-owned subsidiaries, had a 50% interest of the joint venture entity, REV-I. For the three months ended March 31, 2026, the Company did not fund REV-I due to the JV Sale. For the three months ended March 31, 2025, the Company funded $1.0 million, associated with the Company’s commitment and its share of REV-I development costs. The Company did not provide any additional financial support outside of capital contributions to REV-I during the three months ended March 31, 2026 and 2025. However, in connection with the joint venture, the Company provided certain scientific and finance and accounting related support which was reimbursed by REV-I to the Company and included in other income on the condensed consolidated statements of operations and comprehensive loss. For the three months ended March 31, 2026 the Company did not provide such support due to the JV Sale. For the three months ended March 31, 2025, the Company recorded $0.2 million related to such support. Prior to the JV Sale, the Company held a 50% interest in the joint venture and based on management’s analysis, the Company was not the primary beneficiary of REV-I and accordingly, the entity was not consolidated in the Company’s condensed consolidated financial statements. For the three months ended March 31, 2026, the Company did not have allocable share of REV-I losses due to the JV Sale. For the three months ended March 31, 2025, the Company recorded its allocable share of REV-I’s losses which totaled $0.6 million. These losses were recorded as a loss on investment in joint venture within the condensed consolidated statements of operations and comprehensive loss. After recognition of its share of losses for the period, there was no carrying value remaining of the REV-I investment as of March 31, 2026 and December 31, 2025.	9. INVESTMENT IN JOINT VENTURE In July 2025, the Company entered into the ENPP1 Purchase Agreement to sell its interest in REV102, an ENPP1 inhibitor in preclinical development for the treatment of patients with HPP, to Buyer (a subsidiary of its joint venture partner Recursion). In connection with the JV Sale, the Company received compensation in the form of Recursion common stock (which is a non-cash investing activity). The Company subsequently sold the Recursion common stock for cash proceeds of $20.0 million in the third quarter of 2025 which included $7.5 million from an upfront payment and $12.5 million from a milestone payment related to the initiation of additional preclinical studies. The Company is eligible to receive a $5.0 million milestone cash payment in connection with the initiation of dosing in a Phase 1 clinical study, as defined in the ENPP1 Purchase Agreement and low single-digit royalties on all future net sales by Recursion of products comprising or incorporating certain compounds developed by REV-I. The Company may also be eligible to receive certain payments in the event of Recursion’s sale of the REV102 program. The Company evaluated the JV Sale under ASC 860, Transfers and Servicing of Financial Assets (“ASC 860”). Based on the Company’s evaluation of the JV Sale under ASC 860, the Company recognized a gain from the sale of its equity interests in REV102 of $22.4 million, based on the excess of the total net consideration allocated to the sale of the Company’s equity interests (based on relative fair value) of $23.0 million over the carrying value of the equity interests sold of $0.6 million. The total net consideration of $23.0 million included cash received of $20.0 million, plus an estimated $3.0 million representing the fair value of the future milestone payments and future royalties (which is a non-cash investing activity). The contingent consideration was initially measured at fair value using a probability based present value model of the risk-adjusted estimated cash flows, with a discount rate of 15.4%. This valuation model relied on significant unobservable inputs (level 3 inputs) based on management’s estimates, which were informed by external data, judgment, and forecasts. Key assumptions included the probability of achieving the milestone and royalties, timing of cash flows, discount rate, and forecasted net revenues. The fair value of the contingent consideration is a non-recurring fair value measurement and is recorded as other assets and other assets, non-current on the Company’s consolidated balance sheets and as gain on sale of joint venture and other income within the Company’s consolidated statements of operations and comprehensive loss. Prior to the JV Sale, the Company, through one of its wholly owned subsidiaries, had a 50 % interest of the joint venture entity, REV-I. For the years ended December 31, 2025 and 2024 the Company funded $ 1.5 million and $ 2.0 million, respectively, associated with the Company’s commitment and its share of REV-I development costs. The Company did no t provide any additional financial support outside of capital contributions to REV-I during the years ended December 31, 2025 and 2024. However, in connection with the joint venture, the Company provided certain scientific and finance and accounting related support which was reimbursed by REV-I to the Company and included in other income on the consolidated statements of operations and comprehensive loss. For the years ended December 31, 2025 and 2024, the Company recorded $ 0.3 million and $ 0.7 million, respectively, related to such support. Prior to the JV Sale, the Company held a 50 % interest in the joint venture and based on management’s analysis, the Company was not the primary beneficiary of REV-I and accordingly, the entity was not consolidated in the Company’s consolidated financial statements. For the years ended December 31, 2025 and 2024, the Company recorded its allocable share of REV-I’s losses, which totaled $0.9 million and $2.2 million, respectively, as a loss on investment in joint venture in the consolidated statements of operations and comprehensive loss. After recognition of its share of losses for the period, the carrying value and maximum exposure to risk of the REV-I investment there was no carrying value remaining on the REV-I investment as of December 31, 2025 or 2024.

Submission	Jul. 15, 2026
Submission [Line Items]
Central Index Key	0001739410
Registrant Name	Rallybio Corp
Form Type	S-4
Submission Type	S-4
Fee Exhibit Type	EX-FILING FEES

STOCKHOLDERS' EQUITY - Summary of Equity-based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation	$ 613	$ 1,879	$ 5,314	$ 7,993
Research and development
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation	184	810	2,250	3,269
General and administrative
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Share-based compensation	$ 429	$ 1,069	$ 3,064	$ 4,724

SEGMENTS

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Segment Reporting [Abstract]

SEGMENTS

9. SEGMENTS

The Company defines its segments on the basis of the way in which internally reported financial information is regularly reviewed by the chief operating decision maker (“CODM”) to analyze financial performance, make decisions, and allocate resources. The Company’s CODM consists of its Chief Executive Officer and Chief Financial Officer. The Company manages its operations as a single operating and reportable segment and the measure of segment profit or loss is net loss. The CODM uses net loss in the budget and forecasting process and considers

budget-to-actual

variances on a quarterly basis when making decisions about the allocation of operating and capital resources.

The following table summarizes the information about reported segment revenues and significant segment expenses presented on the Company’s condensed consolidated statements of operations and comprehensive loss for the three months ended March 31, 2026 and 2025:


	FOR THE THREE MONTHS ENDED MARCH 31,
(in thousands)	2026			2025
Revenue	$	212		$	212
Less:
Research and development:
RLYB212		56			2,438
RLYB116		396			619
Other program candidates		2			(163	)
Personnel expenses (including share-based compensation)		2,280			2,589
Other expenses		137			242
General and administrative, excluding personnel expenses		4,223			1,525
General and administrative, personnel expenses (including share-based compensation)		1,851			2,632
Other segment items*		(455	)		(231	)

Segment net loss	$	(8,278	)	$	(9,439	)

*	Other segment items include total other income, net and loss on investment in joint venture.

12. SEGMENTS

The Company defines its segments on the basis of the way in which internally reported financial information is regularly reviewed by the CODM to analyze financial performance, make decisions, and allocate resources. The Company’s CODM consists of its Chief Executive Officer, Chief Financial Officer and Chief Medical Officer. The Company manages its operations as a single operating and reportable segment and the measure of segment profit or loss is net loss. The CODM uses net loss in the budget and forecasting process and considers

budget-to-actual

variances on a quarterly basis when making decisions about the allocation of operating and capital resources.

The following table summarizes the information about reported segment revenues and significant segment expenses presented on the Company’s consolidated statements of operations and comprehensive loss for the years ended December 31, 2025 and 2024:


	FOR THE YEAR ENDED DECEMBER 31,
(in thousands)	2025			2024
Revenue	$	858		$	636
Less:
Research and development:
RLYB212		6,291			21,287
RLYB116		3,786			4,841
Other program candidates		(29	)		1,901
Personnel (including share-based compensation)		8,798			12,488
Other		751			990
General and administrative, excluding personnel		6,078			6,654
General and administrative, personnel (including share-based compensation)		8,247			12,971
Other segment items*		(24,086	)		(2,721	)

Segment net loss	$	(8,978	)	$	(57,775	)

Other segment items includes total other income, net and gain and loss on investment in joint venture.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-31

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-15

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 48
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 11: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 12: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 14: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 15: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 16: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 17: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-34

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26C

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26B

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/280/tableOfContent

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

+ Details

STOCKHOLDERS' EQUITY - Summary of Assumptions of Fair Value of Option Pricing Granted (Details) - Employee Stock Options - 2021 Equity Incentive Plan - $ / shares	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected volatility	109.21%
Expected volatility, minimum			91.88%	89.41%
Expected volatility, maximum			119.61%	94.48%
Expected term (years)	5 years 3 months
Risk-free interest rate	3.68%
Risk-free interest rate, minimum			4.36%	3.93%
Risk-free interest rate, maximum			4.39%	4.35%
Expected dividend yield	0.00%		0.00%	0.00%
Exercise price (in dollars per share)	$ 4.45
Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (years)			5 years 3 months 7 days	5 years 6 months
Exercise price (in dollars per share)		$ 6.08	$ 2.38	$ 14.88
Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (years)		6 years 7 days	6 years 7 days	6 years 7 days
Exercise price (in dollars per share)		$ 7.6	$ 7.6	$ 19.2

LEASES

12 Months Ended

Dec. 31, 2025

Leases [Abstract]

LEASES

5. LEASES

The Company has an operating lease for approximately

four thousand

five hundred square feet of corporate office space. The weighted-average remaining lease term as of December 31, 2025 was

1 year, 9 months

. The weighted-average discount rate utilized on our operating lease liabilities as of December 31, 2025 was 9.00%.

Operating leases are included in operating lease ROU assets, operating lease liabilities, and operating lease liabilities, noncurrent in our consolidated balance sheets as of December 31, 2025 and 2024.

The following table summarizes the presentation of the Company’s operating lease as presented on the consolidated balance sheets:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Assets:
Operating lease right-of-use assets	$	175	$	152

Liabilities:
Operating lease liabilities	$	94	$	154
Operating lease liabilities, noncurrent		82		—

Total operating lease liabilities	$	176	$	154

Future minimum lease payments from December 31, 2025 until the expiration of the operating lease are as follows:


(in thousands)
2026	$	106
2027		84
Thereafter		—

Total lease payments		190
Less: imputed discount rate		(14	)

Carrying value of operating lease liabilities	$	176

The Company incurred $0.2 million in operating lease rent expense for both years ended December 31, 2025 and 2024. Lease payments made were $0.2 million and $0.3 million for the years ended December 31, 2025 and 2024, respectively, with such amounts reflected on the consolidated statements of cash flows in operating activities.

BALANCE SHEET COMPONENTS - Schedule of Prepaid Expenses and Other Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Balance Sheet Related Disclosures [Abstract]
Research and development	$ 595	$ 3,372	$ 697
Insurance	231	409	424
Other prepaids	135	219	214
Other current assets	5,734	2,517	995
Prepaid expenses and other assets	$ 6,695	$ 6,517	$ 2,330

BALANCE SHEET COMPONENTS - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Mar. 31, 2026
Balance Sheet Related Disclosures [Abstract]
Depreciation expense	$ 0.1	$ 0.1
Other Receivables, Gross, Current			$ 3.4
Future Contingent Milestone And Royalty Assets Current			2.2
Other Assets, Miscellaneous, Current			$ 0.1

RESTRUCTURING AND SEVERANCE

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Restructuring and Related Activities [Abstract]

RESTRUCTURING AND SEVERANCE

10. RESTRUCTURING AND SEVERANCE

In connection with entering into the Merger Agreement and the potential Merger, the Company incurred severance charges of approximately $2.3 million of which $1.6 million was included in research and development expenses and $0.7 million was included in general and administrative expenses, with such amounts reflected in the condensed consolidated statements of operations and comprehensive loss. The charges related to the Merger Agreement were cash-based expenditures related primarily to severance and benefit payments. The Company recognized all such charges during the first quarter of 2026, with such amounts reflected in the condensed consolidated statements of operations and comprehensive loss. The accrued severance liability is included in accrued expenses in the condensed consolidated balance sheets as of March 31, 2026.

On May 2, 2025, the Company approved a workforce reduction to focus resources on the Company’s lead program, RLYB116, and its preclinical development programs.

As part of this effort, the Company eliminated approximately 40% of its positions. As a result of these actions, the Company incurred charges of approximately $1.7 million of which $1.2 million was included in research and development expenses and $0.5 million was included in general and administrative expenses, with such amounts reflected in the condensed consolidated statements of operations and comprehensive loss. The charges related to the workforce reduction were cash-based expenditures related primarily to severance and benefit payments. The Company recognized all such charges during the second quarter of 2025, with such amounts reflected in the condensed consolidated statements of operations and comprehensive loss. The accrued restructuring liability is included in accrued expenses in the condensed consolidated balance sheets as of March 31, 2026.

All restructuring and severance payments related to the terminated Merger are expected to be paid within the next 12 months.

The following table summarizes the restructuring accrual activity as of March 31, 2026:


(in thousands)	MARCH 31, 2026
Beginning accrued severance as of January 1, 2026	$	523
Severance incurred during the period		2,302
Severance paid and adjustments made during the period		(1,449	)

Ending accrued severance as of March 31, 2026	$	1,376

13. RESTRUCTURING

On May 2, 2025, the Company approved a workforce reduction to focus resources on the Company’s lead program, RLYB116 and its preclinical development programs.

As part of this effort, the Company eliminated approximately 40% of its positions. As a result of these actions, the Company incurred charges of approximately $1.7 million of which $1.2 million was included in research and development expenses and $0.5 million was included in general and administrative expenses, with such amounts reflected in the consolidated statements of operations and comprehensive loss. The charges related to the workforce reduction were cash-based expenditures related primarily to severance and benefit payments. The Company recognized all such charges during the second quarter of 2025, with such amounts reflected in the consolidated statements of operations and comprehensive loss. The accrued restructuring liability is included in accrued expenses in the consolidated balance sheets as of December 31, 2025.

In February, 2024, the Company announced a prioritization of its portfolio and a workforce reduction to focus resources primarily on the continued development of RLYB212.

As part of this effort, the Company eliminated approximately 45% of its positions. As a result of these actions, the Company incurred charges of approximately $3.3 million of which $2.0 million was included in research and development expenses and $1.3 million was included in general and administrative expenses, with such amounts reflected in the consolidated statements of operations and comprehensive loss. The charges related to the workforce reduction are cash-based expenditures related primarily to severance and benefit payments. The Company recognized all such charges in the first quarter of 2024, with such amounts reflected in the consolidated statements of operations and comprehensive loss.

Substantially all restructuring payments are expected to be completed by August 2026.

The following table summarizes the restructuring accrued expense activity as of December 31, 2025:


(in thousands)	DECEMBER 31, 2025
Beginning accrued severance	$	203
Severance incurred during the period		1,706
Severance paid and adjustments made during the period		(1,386	)

Ending accrued severance	$	523

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2025

Income Tax Disclosure [Abstract]

Schedule of Income before Income Tax, Domestic and Foreign

The following table summarizes income (loss) before income taxes:


(in thousands)	2025
Domestic	$	(8,978	)
Foreign		—

Total	$	(8,978	)

Schedule of Effective Income Tax Rates

The following is a reconciliation from the Company’s statutory rate to the effective tax rate reported in the financial statements:


	2025
(in thousands)	Amount			Rate
Statutory federal income tax rate	$	(1,885	)		21.0	%
Tax credits (federal):
Orphan drug credit		(1,331	)		14.8	%
Other		(231	)		2.6	%
Valuation allowance		2,203			(24.5	%)
Non-deductible or non-taxable items:
Share-based compensation		1,227			(13.7	)%
Other adjustments		17			(0.2	%)

Effective income tax rate	$	—			0.0	%


	2024
U.S. federal statutory income tax rate		21.0	%
State income taxes, net of federal income tax benefit		5.4	%
Tax credits		10.7	%
Other		(2.9	)%
Valuation allowance		(34.2	)%

Effective income tax rate		—	%

Schedule of Deferred Income Tax Benefits and Liabilities


(in thousands)	2025			2024
Net operating loss carryforwards	$	50,322		$	45,973
Amortization		1,775			1,341
Section 174 capitalization		19,947			22,479
Research and development tax credits		25,701			24,047
Share-based compensation		2,405			2,654
Other		301			1,476

Total deferred tax assets		100,451			97,970
Valuation allowance		(100,451	)		(97,970	)

Net deferred tax assets	$	—		$	—

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION

Unaudited Financial Information—

These accompanying unaudited condensed consolidated financial statements and notes should be read in conjunction with Rallybio’s Annual Report on Form

10-K

Significant Accounting Policies —

Future Milestone and Royalty Assets

Recently Issued Accounting Pronouncements

—In November 2024, the FASB issued ASU

2024-03,

Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic

220-40):

Disaggregation of Income Statement Expenses (

“ASU

2024-03”).

This ASU requires public entities to disclose additional transparency on certain costs and expenses. ASU

2024-03

2. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION

Basis of Presentation—

In the opinion of the Company, the information furnished reflects all adjustments, all of which are of a normal and recurring nature, necessary for a fair presentation of the financial position and results of operations for the reported periods. The Company considers events or transactions that occur after the balance sheet date but before the financial statements are issued to provide additional evidence relative to certain estimates or to identify matters that require additional disclosure.

On February 6, 2026, the Company executed a reverse stock split of its issued and outstanding common stock, par value $0.0001, at a ratio of

1-for-8

Principles of Consolidation

—The consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.

Use of Estimates

Liquidity and Ability to Continue as a Going Concern

Collaboration Arrangements

Collaborative Arrangements

For arrangements determined to be within the scope of ASC 808 for certain research and development activities where a collaborative partner is not a customer following the guidance of ASC 606,

Revenue Recognition

Asset Acquisitions

in-process

Variable Interest Entity

(“REV-I”),

Equity Method Investments

—The Company accounts for investments for which it does not have a controlling interest in accordance with ASC 323,

Investments—Equity Method and Joint Ventures

(“ASC 323”). The Company recognizes its

pro-rata

Financial Instruments

Concentrations of Credit Risk

Cash and Cash Equivalents

Marketable Securities

—We invest our excess cash balances in highly rated United States (“U.S.”) government-backed debt securities and treasuries. We classify our marketable securities as

available-for-sale

and accordingly, record such securities at fair value. Debt securities with original maturities of greater than 90 days are classified as

available-for-sale

marketable securities and debt securities with original maturities of less than 90 days from the date of purchase are classified as cash equivalents.

Property and Equipment


Asset Classification		Estimated Useful Life
Computer and other equipment		3 years
Capitalized software		3 years
Furniture and fixtures		6 years
Leasehold improvements		lesser of lease life or useful life

Impairment of Long-Lived Assets

Leases

non-lease

components, (ii) determine the consideration in the contract, (iii) determine whether the lease is an operating or financing lease; and iv) recognize lease

right-of-use

We have elected to combine lease components with

non-lease

Income Taxes

—The Company uses the asset and liability method of accounting for income taxes, as set forth in ASC 740,

Accounting for Income Taxes

(“ASC 740”). Under this method, deferred tax assets and liabilities are recognized for the expected future tax consequence of temporary differences between the carrying amounts and the

tax-planning

The Company files a consolidated U.S. federal income tax return and has elected to include all subsidiaries owned more than 80%.

The Company recognizes and measure uncertain tax benefits in accordance with ASC 740 based on a

two-step

more-likely-than-not

Research and Development Expenses

Stock Warrants

Distinguishing Liabilities from Equity

(“ASC 480”) and ASC 815,

Derivatives and Hedging

paid-in

Share-Based Compensation

—The Company accounts for share-based compensation in accordance with ASC 718,

Compensation—Stock Compensation

Fair Value Measurements

—ASC Topic 820,

Fair Value Measurement

Level 1—Quoted market prices in active markets for identical assets or liabilities.

Level 2—Inputs other than Level 1 inputs that are either directly or indirectly observable, such as quoted market prices, interest rates and yield curves.

Future Milestone and Royalty Assets

As part of the JV Sale, the Company received consideration including an estimated $3.0 million in future contingent milestones and royalty payments, which are recognized as a contingent consideration asset within prepaid expenses and other current assets on the consolidated balance sheets. The fair value of this contingent consideration was determined using a model that incorporates significant unobservable inputs based on Company estimates, external data, and management’s judgment and forecasts. Key assumptions in the model include the discount rate, the timing of expected cash flows, the probability of achieving the milestone and royalty payments, and projected future net revenues.

Segment Information

Basic and Diluted Net Loss Per Share

pre-funded

Revenue Recognition

—The Company recognizes revenue in accordance with the provisions of ASC Topic 606,

Revenue from Contracts with Customers

know-how,

Restructuring

—The Company accounts for restructuring charges in accordance with ASC Subtopic

420-10,

Exit or Disposal Cost Obligations

Recently Adopted Accounting Pronouncements

—In December 2023, the FASB issued, ASU

2023-09,

Income Taxes (Topic 740):

Improvements to Income Tax Disclosures

(“ASU

2023-09”)

2023-09

were early adopted by the Company on a prospective basis. There was no material impact to the Company’s financial statements as a result of adopting ASU

2023-09.

See Note 8, “Income Taxes” for additional detail.

In May 2025, the FASB issued ASU

2025-03,

Business Combinations (Topic 805) and Consolidation (Topic 810):

Determining the Accounting Acquirer in the Acquisition of a Variable Interest Entity

(“ASU

2025-03”),

2025-03.

Recently Issued Accounting Pronouncements

—In November 2024, the FASB issued ASU

2024-03,

Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic

220-40):

Disaggregation of Income Statement Expenses (

“ASU

2024-03”).

This ASU requires public entities to disclose additional transparency on certain costs and expenses. ASU

2024-03

COLLABORATION AND LICENSE AGREEMENTS - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended			12 Months Ended
	Apr. 30, 2024	Mar. 31, 2026	Mar. 31, 2025	Jun. 30, 2022	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2022	Apr. 30, 2025
Schedule of License and Collaboration Agreements [Line Items]
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001			$ 0.0001	$ 0.0001
Total revenue		$ 212	$ 212		$ 858	$ 636
Research and development		2,871	$ 5,725		19,597	41,507
AbCellera Collaboration
Schedule of License and Collaboration Agreements [Line Items]
Research and development					0	400
License
Schedule of License and Collaboration Agreements [Line Items]
Total revenue					800	600
License Agreement \| Sanofi
Schedule of License and Collaboration Agreements [Line Items]
Upfront payment				$ 3,000
Aggregate development and regulatory milestone payments					43,000
Obligation to payment upon maximum achievement of certain clinical and commercial milestones					150,000
License Agreement \| Sanofi \| License Rights
Schedule of License and Collaboration Agreements [Line Items]
Transaction costs associated with asset acquisition							$ 100
License Agreement \| Sanofi \| License Rights \| IPR&D
Schedule of License and Collaboration Agreements [Line Items]
Research and development					$ 0	$ 0	$ 3,100
Collaboration [Member]
Schedule of License and Collaboration Agreements [Line Items]
Total revenue		$ 200
Johnson & Johnson \| Securities Purchase Agreement
Schedule of License and Collaboration Agreements [Line Items]
Sale of stock, number of shares issued in transaction (in shares)	454,545
Sale of stock, price per share (in dollars per share)	$ 14.56
Sale of stock, premium on stock price (as a percent)	10.00%
Gross proceeds	$ 6,600
Allocated amounts	1,200
Johnson & Johnson \| Securities Purchase Agreement \| Fair Value, Nonrecurring
Schedule of License and Collaboration Agreements [Line Items]
Fair value	5,400
Johnson & Johnson \| Securities Purchase Agreement \| Measurement Input, Premium
Schedule of License and Collaboration Agreements [Line Items]
Allocated amounts	700
Johnson & Johnson \| Securities Purchase Agreement \| Measurement Input, Discount for Lack of Marketability
Schedule of License and Collaboration Agreements [Line Items]
Allocated amounts	$ 500
Johnson & Johnson \| Securities Purchase Agreement \| Measurement Input, Price Volatility \| Fair Value, Nonrecurring
Schedule of License and Collaboration Agreements [Line Items]
Measurement input	1.132
Johnson & Johnson \| Securities Purchase Agreement \| Measurement Input, Risk Free Interest Rate \| Fair Value, Nonrecurring
Schedule of License and Collaboration Agreements [Line Items]
Measurement input	0.0528
Johnson & Johnson \| License
Schedule of License and Collaboration Agreements [Line Items]
Collaboration agreement term	2 years
Upfront payment								$ 500
Johnson & Johnson \| License Agreement
Schedule of License and Collaboration Agreements [Line Items]
Collaboration agreement term	2 years

STOCKHOLDERS' EQUITY - Summary of Unvested Restricted Common Stock Units (Details) - Restricted Stock Units (RSUs) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Shares
Outstanding, beginning balance (in shares)	38,603	133,069
Granted (in shares)	5,000	59,500
Forfeited (in shares)	(4,150)	(66,646)
Vested (in shares)	(6,354)	(87,320)
Outstanding, ending balance (in shares)	33,099	38,603
Weighted-Average Grant Date Fair Value Per Share
Outstanding, beginning balance (in dollars per share)	$ 9.6	$ 18.89
Granted (in dollars per share)	4.45	5.96
Forfeited (in dollars per share)	2.4	12.34
Vested (in dollars per share)	7.79	19.18
Outstanding, ending balance (in dollars per share)	$ 10.07	$ 9.6

INCOME TAXES - Schedule of Income before Income Tax, Domestic and Foreign (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Schedule of Income before Income Tax, Domestic and Foreign [Line Items]
Net Income (Loss)	$ (8,278)	$ (9,439)	$ (8,978)	$ (57,775)
Domestic [Member]
Schedule of Income before Income Tax, Domestic and Foreign [Line Items]
Net Income (Loss)			(8,978)
Foreign [Member]
Schedule of Income before Income Tax, Domestic and Foreign [Line Items]
Net Income (Loss)			$ 0

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479168/946-830-55-10

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-4

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-21

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 480
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479857/480-10-S50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 480
-SubTopic 10
-Name Accounting Standards Codification
-Section S45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479887/480-10-S45-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 480
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3A
-Subparagraph (24)(d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480244/480-10-S99-3A

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 105
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 19: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482765/220-10-50-6

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479105/946-220-45-7

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(1)(d))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 34: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 37: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 38: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 39: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 40: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 41: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 42: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 43: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 44: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483499/205-20-50-7

Reference 45: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 46: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A

Reference 47: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B

Reference 48: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

Reference 49: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

INCOME TAXES - Schedule of Effective Income Tax Rates (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Income Tax Disclosure [Abstract]
Statutory federal income tax rate	$ (1,885,000)
Tax credits (federal):
Orphan drug credit	(1,331,000)
Other	(231,000)
Valuation allowance	2,203,000
Non-deductible or non-taxable items:
Share-based compensation	1,227,000
Other adjustments	17,000
Effective income tax rate	$ 0	$ 0
U.S. federal statutory income tax rate	21.00%	21.00%
State income taxes, net of federal income tax benefit		5.40%
Tax credits (federal):
Orphan drug credit	14.80%
Other	2.60%	(2.90%)
Tax credits		10.70%
Valuation allowance	(24.50%)	(34.20%)
Non-deductible or non-taxable items:
Share-based compensation	(13.70%)
Other adjustments	(0.20%)
Effective income tax rate	0.00%	0.00%

Offerings - Offering: 1	Jul. 15, 2026 USD ($) shares
Offering:
Fee Previously Paid	false
Other Rule	true
Security Type	Equity
Security Class Title	Common Stock, par value $0.0001 per share
Amount Registered \| shares	197,484,269
Maximum Aggregate Offering Price	$ 6,582.81
Fee Rate	0.01381%
Amount of Registration Fee	$ 0.91
Offering Note	(1) Relates to common stock, par value $0.0001 per share ("Rallybio Common Stock"), of Rallybio Corporation, a Delaware corporation ("Rallybio"), issuable to holders of shares of Class A common stock, par value $0.0001 per share ("Avenzo Common Stock"), shares of preferred stock, par value $0.0001 per share ("Avenzo Preferred Stock"), and outstanding unexercised options to purchase shares of Avenzo Common Stock that will be assumed by Rallybio and converted into options to purchase shares of Rallybio Common Stock ("Avenzo Options," and together with the Avenzo Common Stock and Avenzo Preferred Stock, "Avenzo Shares"), of Avenzo Therapeutics, Inc., a Delaware corporation ("Avenzo"), in the merger of Farmington Merger Sub, Inc., a Delaware corporation and wholly-owned subsidiary of Rallybio, with and into Avenzo, with Avenzo surviving as a wholly-owned subsidiary of Rallybio. The amount of Rallybio Common Stock to be registered includes the estimated maximum number of shares of Rallybio Common Stock that are expected to be issued (or become issuable) pursuant to the merger, without taking into account the effect of a reverse stock split of the Rallybio Common Stock, assuming an estimated pre-split exchange ratio (which is subject to adjustment prior to the closing of the merger) of approximately 0.5020 shares of Rallybio Common Stock for each Avenzo Share. Such exchange ratio is only an estimate as the actual exchange ratio will be determined in connection with the closing of the merger. In accordance with Rule 416 under the Securities Act of 1933, as amended (the "Securities Act"), this registration statement shall be deemed to cover any securities that may from time to time be offered or issued resulting from forward or reverse stock splits, stock dividends or similar transactions. (2) Estimated solely for purposes of calculating the registration fee in accordance with Rule 457(f)(2) of the Securities Act. Avenzo is a private company, no market exists for its securities, and it has an accumulated capital deficit. Therefore, the proposed maximum aggregate offering price for the shares expected to be issued (or become issuable) in the merger is one-third of the aggregate par value of the Avenzo securities expected to be exchanged for the shares of Rallybio Common Stock being registered, including any Rallybio Common Stock issuable upon exercise of the Avenzo Options.

INVESTMENT IN JOINT VENTURE (Details)	3 Months Ended			12 Months Ended
INVESTMENT IN JOINT VENTURE (Details)	Mar. 31, 2026 USD ($)	Sep. 30, 2025 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)	Jun. 30, 2025 USD ($)
Schedule of Equity Method Investments [Line Items]
Investment in joint venture	$ 0		$ 1,000,000	$ 1,500,000	$ 2,000,000
Allocable share of losses recorded	0		(587,000)	(874,000)	(2,239,000)
Equity Method Investment, Realized Gain (Loss) on Disposal				22,350,000	$ 0
Future Contingent Milestone And Royalty Assets	$ 3,000,000			$ 3,000,000
RE Ventures I, LLC
Schedule of Equity Method Investments [Line Items]
Percentage of interest of joint venture entity	50.00%			50.00%	50.00%
Investment in joint venture	$ 0		1,000,000	$ 1,500,000	$ 2,000,000
Additional financial support outside of capital contribution	0		0	0	0
Scientific and finance & accounting support	0		200,000	300,000	700,000
Allocable share of losses recorded	$ 0		$ 600,000	900,000	2,200,000
Investment in joint venture				$ 0	$ 0
Proceeds from Sale of Equity Method Investments		$ 20,000,000
Proceeds From Sale Of Equity Method Investments, Upfront Payment Received		7,500,000
Proceeds From Sale Of Equity Method Investments, Milestone Payment Received		12,500,000
Future Equity Method Investment, Milestone, Cash Payment		$ 5,000,000
Discount Rate Used To Estimated Future Contingent Milestone And Royalties		0.154
Equity Method Investment, Realized Gain (Loss) on Disposal		$ 22,400,000
Equity Method Investment, Net Consideration		23,000,000
Equity Method Investments		600,000				$ 600,000
Future Contingent Milestone And Royalty Assets		$ 3,000,000

Cover	3 Months Ended
Cover	Mar. 31, 2026
Document Information [Line Items]
Document Type	S-4
Entity Registrant Name	RALLYBIO CORPORATION
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	85-1083789
Entity Address, Address Line One	PO Box no. 325
Entity Address, City or Town	East Berlin
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06023
City Area Code	203
Local Phone Number	859-3820
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Central Index Key	0001739410
Amendment Flag	false
Entity Primary SIC Number	2834
Business Contact [Member]
Document Information [Line Items]
Entity Address, Address Line One	PO Box no. 325
Entity Address, City or Town	East Berlin
Entity Address, State or Province	CT
Entity Address, Postal Zip Code	06023
City Area Code	203
Local Phone Number	859-3820
Contact Personnel Name	Stephen Uden, M.D.

STOCKHOLDERS' EQUITY

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Equity [Abstract]

STOCKHOLDERS' EQUITY

5. STOCKHOLDERS’ EQUITY

Common Stock

In April 2024, the Company entered into a securities purchase agreement (the “JJDC Securities Purchase Agreement”) with Johnson & Johnson Innovation - JJDC, Inc. (“JJDC”), pursuant to which the Company sold to JJDC, in an unregistered offering, 454,545 shares of its common stock, at a price of $14.56 per share, which represented a 10% premium on the Company’s closing stock price on April 9, 2024, for aggregate gross proceeds of approximately $6.6 million, before deducting offering expenses.

The Company had 200,000,000 shares of common stock authorized as of March 31, 2026 and December 31, 2025, of which 5,290,236 and 5,283,321 shares were issued and outstanding as of March 31, 2026 and December 31, 2025, respectively.

Preferred Stock

The Company had 50,000,000 shares of preferred stock authorized as of March 31, 2026 and December 31, 2025, of which no shares were issued or outstanding as of March 31, 2026 and December 31, 2025.

Pre-Funded

Warrants

In connection with a

follow-on

offering, the Company entered into an agreement with certain investors to issue

pre-funded

warrants in lieu of common stock to purchase up to an aggregate of 416,673 shares of common stock at a price of $47.9992, which represents the per share public offering price of the November 2022

follow-on

offering for common stock less a $0.0008 per share exercise price for each

pre-funded

warrant.

The Company may not effect the exercise of any

pre-funded

warrant, and a holder will not be entitled to exercise any portion of any

pre-funded

warrant if, upon giving effect to such exercise, the aggregate number of shares of common stock beneficially owned by the holder (together with its affiliates) would exceed 9.99% of the number of shares of common stock outstanding immediately after giving effect to the exercise, which percentage may be increased or decreased at the holder’s election upon 61 days’ notice to the Company subject to the terms of such

pre-funded

warrants, provided that such percentage may in no event exceed 19.99%.

The Company’s

pre-funded

warrant is a freestanding instrument that does not meet the definition of a liability pursuant to ASC 480,

Distinguishing Liabilities from Equity

(“ASC 480”)

and does not meet the definition of a derivative pursuant to ASC 815,

Derivatives and Hedging

(“ASC 815”). The

pre-funded

warrant is indexed to the Company’s common stock and meets all other conditions for equity classification under ASC 480 and ASC 815.

Accordingly, the

pre-funded

warrant was classified as equity and accounted for as a component of additional

paid-in

capital at the time of issuance. All of the

pre-funded

warrants related to the November 2022

follow-on

offering remain outstanding and unexercised as of March 31, 2026.

Share-based Compensation


	FOR THE THREE MONTHS ENDED MARCH 31,
(in thousands)	2026		2025
Research and development	$	184	$	810
General and administrative		429		1,069

	$	613	$	1,879

2021 Equity Incentive Plan

In 2021, the board of directors adopted the Rallybio Corporation 2021 Equity Incentive Plan (the “2021 Plan”). The 2021 Plan initially reserved 680,043 shares of the Company’s common stock that have been issued in respect of outstanding equity awards granted prior to the Company’s initial public offering (“IPO”), and for future issuances of shares to employees, directors and consultants in the form of stock options, SARs, restricted and unrestricted stock and stock units, performance awards and other awards that are convertible into or otherwise based on the Company’s common stock. Dividend equivalents may also be provided in connection with awards under the 2021 Plan. The share pool will automatically increase on January 1st of each year until 2031, by the lesser of (i) five percent of the number of shares of the Company’s common stock outstanding as of such date and (ii) the number of shares of the Company’s common stock determined by the board of directors on or prior to such date. On January 1, 2026 and January 1, 2025, the 2021 Plan share pool was automatically increased by 264,166 and 259,438 shares, respectively. As of March 31, 2026, the total number of shares of the Company’s common stock that were issuable under the 2021 Plan was 1,514,824 shares, of which 834,331 shares remained available for future issuance.

The following table summarizes stock option activity for the three months ended March 31, 2026:


Stock Options	Number of Option Shares			Weighted- Average Exercise Price		Weighted- Average Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding stock options at December 31, 2025		628,280		$	43.42		7.6	$	89
Granted		32,360		$	4.45
Forfeited		(11,404	)	$	15.70
Expired		(1,281	)	$	88.75
Exercised		(561	)	$	6.08

Outstanding stock options at March 31, 2026		647,394		$	41.90		6.2	$	749

Exercisable stock options at March 31, 2026		427,642		$	56.52		5.6	$	180

The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock options and the estimated fair value of the Company’s common stock. Stock options outstanding with an exercise price below the closing price as of March 31, 2026 had an intrinsic value of approximately $749 thousand. Stock

options outstanding and exercisable with an exercise price below the closing price as of March 31, 2026 had an intrinsic value of $180 thousand. These values are based on a common stock fair value of $8.97 per share, which was the closing price of the Company’s common stock on March 31, 2026. Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the three months ended March 31, 2026 and 2025 was $3.60 per share and $5.36 per share, respectively. As of March 31, 2026, there was unrecognized share-based compensation expense related to nonvested stock options of $2.2 million, which the Company expects to recognize over a weighted-average period of approximately 1.6 years. As of March 31, 2026, in connection with the consummation of the

now-terminated

proposed Merger, all nonvested stock options were expected to vest and the remaining expense would have been recognized.

The fair value of the stock options granted during the three months ended March 31, 2026 and 2025 was determined using the Black-Scholes option pricing model with the following assumptions:


	FOR THE THREE MONTHS ENDED MARCH 31,
	2026		2025
Expected volatility		109.21%		91.88%–119.61%
Expected term (years)		5.25		5.27–6.02
Risk free interest rate		3.68%		4.36%–4.39%
Expected dividend yield		—		—
Exercise price	$	4.45	$	6.08–$7.60

A summary of the status of the Company’s nonvested restricted common stock units at March 31, 2026 and changes during the three months ended March 31, 2026 was as follows:


Restricted Stock Units	Shares			Weighted- Average Grant Date Fair Value Per Share
Nonvested restricted stock units at December 31, 2025		38,603		$	9.60
Granted		5,000		$	4.45
Forfeited		(4,150	)	$	2.40
Vested		(6,354	)	$	7.79

Nonvested restricted stock units at March 31, 2026		33,099		$	10.07

As of March 31, 2026, there was unrecognized share-based compensation expense related to nonvested restricted stock units of $0.2 million, which the Company expects to recognize over a weighted-average period of approximately 2.0 years. As of March 31, 2026, in connection with the consummation of the

now-terminated

proposed Merger, all nonvested restricted stock units were expected to vest and the remaining expense would have been recognized.

2021 Employee Stock Purchase Plan

In connection with the Company’s IPO, the board of directors adopted the Rallybio Corporation 2021 Employee Stock Purchase Plan (the “2021 ESPP”), which initially reserved 36,415 shares of the Company’s common stock for future issuances under this plan. The share pool will automatically increase on January 1st of each year from 2022 to 2031, by the lesser of (i) one percent of the number of shares of the Company’s common stock outstanding as of such date, (ii) 72,831 shares of the Company’s common stock and (iii) the number of shares of the Company’s common stock determined by the board of directors on or prior to such date. The 2021 ESPP share pool did not increase on January 1, 2026 or January 1, 2025. As of March 31, 2026, the total number of shares of the Company’s common stock available for future issuance under the 2021 ESPP was 94,281 shares. During the three months ended March 31, 2026 and 2025, the Company did not issue any of the Company’s common stock under the 2021 ESPP.

The 2021 ESPP allows eligible participants to purchase shares of the Company’s common stock through authorized payroll deductions. The purchase price of the shares will not be less than 85% of the lower of the fair market value of the Company’s common stock on the first day of an offering or on the date of the purchase.

7. STOCKHOLDERS’ EQUITY

Common Stock

In April 2024, the Company entered into the JJDC Securities Purchase Agreement, pursuant to which the Company sold to JJDC, in an unregistered offering, 454,545 shares of its common stock, at a price of $14.56 per share, which represents a 10% premium on the Company’s closing stock price on April 9, 2024, for aggregate gross proceeds of approximately $6.6 million, before deducting offering expenses.

The Company had 200,000,000 shares of common stock authorized as of December 31, 2025 and 2024, of which 5,283,321 and 5,188,743 shares were issued and outstanding as of December 31, 2025 and 2024, respectively.

Preferred Stock

The Company had 50,000,000 shares of preferred stock authorized as of December 31, 2025 and 2024, of which no shares were outstanding as of December 31, 2025 and 2024.

Pre-Funded

Warrants

In connection with the November 2022

follow-on

offering, the Company entered into an agreement with certain investors for

pre-funded

warrants in lieu of common stock to purchase up to an aggregate of 416,673 shares of common stock at a price of $47.9992, which represents the per share public offering price at the November 2022

follow-on

offering for common stock less a $0.0008 per share exercise price for each

pre-funded

warrant.

The Company may not effect the exercise of any

pre-funded

warrant, and a holder will not be entitled to exercise any portion of any

pre-funded

warrants, provided that such percentage may in no event exceed 19.99%.

The Company’s

pre-funded

warrant is a freestanding instrument that does not meet the definition of a liability pursuant to ASC 480 and does not meet the definition of a derivative pursuant to ASC 815. The

pre-funded

warrant

is indexed to the Company’s common stock and meets all other conditions for equity classification under ASC 480 and ASC 815. Accordingly, the

pre-funded

warrant was classified as equity and accounted for as a component of additional

paid-in

capital at the time of issuance. All of the

pre-funded

warrants related to our November 2022

follow-on

offering remain outstanding and unexercised as of December 31, 2025.

Share-based Compensation

Share-based compensation is comprised of the Company’s stock options, restricted stock awards, restricted stock units and shares issued pursuant to the employee stock purchase plan, and is classified in the consolidated statements of operations and comprehensive loss for the years ended December 31, 2025 and 2024 and was as follows:


	FOR THE YEAR ENDED DECEMBER 31,
(in thousands)	2025		2024
Research and development	$	2,250	$	3,269
General and administrative		3,064		4,724

	$	5,314	$	7,993

2021 Equity Incentive Plan

In 2021, the board of directors adopted the Rallybio Corporation 2021 Equity Incentive Plan (the “2021 Plan”). The 2021 Plan initially reserved 680,043 shares of the Company’s common stock that have been issued in respect of outstanding equity awards granted prior to the registrant’s IPO and for future issuances of shares to employees, directors and consultants in the form of stock options, SARs, restricted and unrestricted stock and stock units, performance awards and other awards that are convertible into or otherwise based on the Company’s common stock. Dividend equivalents may also be provided in connection with awards under the 2021 Plan. The share pool will automatically increase on January 1st of each year until 2031 by the lesser, of (i) five percent of the number of shares of the Company’s common stock outstanding as of such date and (ii) the number of shares of the Company’s common stock determined by the board of directors on or prior to such date. On January 1, 2025 and January 1, 2024, the 2021 Plan share pool was automatically increased by 259,438 and 236,434 shares, respectively. As of December 31, 2025, the total number of shares of the Company’s common stock that were issuable under the 2021 Plan was 1,257,573 shares, of which 590,690 shares remained available for future issuance.

The following table summarizes stock option activity for the year ended December 31, 2025:


Stock Options	Number of Option Shares			Weighted- Average Exercise Price		Weighted- Average Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding stock options at December 31, 2024		529,342		$	62.83		7.8	$	—
Granted		224,179		$	5.87
Forfeited		(51,758	)	$	32.54
Expired		(73,483	)	$	76.34
Exercised		—		$	—

Outstanding at December 31, 2025		628,280		$	43.42		7.6	$	89

Exercisable stock options at December 31, 2025		399,047		$	58.72		7.1	$	—

The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying stock options and the estimated fair value of the Company’s common stock. Stock options outstanding with an exercise price below the closing price as of December 31, 2025 had an intrinsic value of approximately $89 thousand based on a common stock fair value of $5.49 per share, which was the closing price of the Company’s common stock on

December 31, 2025. Stock options outstanding and exercisable with an exercise price above the closing price as of December 31, 2025 are considered to have

intrinsic value. Using the Black-Scholes option pricing model, the weighted-average grant date fair value of stock options granted during the years ended December 31, 2025 and 2024 was $4.92 per share and $11.78 per share, respectively. As of December 31, 2025, there was unrecognized share-based compensation expense related to nonvested stock options of $2.8 million, which the Company expects to recognize over a weighted-average period of approximately 1.9 years.

The fair value of the stock options granted during the years ended December 31, 2025 and 2024 was determined using the Black-Scholes option pricing model with the following assumptions:


	FOR THE YEAR ENDED DECEMBER 31,
	2025		2024
Expected volatility		91.88% - 119.61%		89.41% - 94.48%
Expected term (years)		5.27 - 6.02		5.50 - 6.02
Risk free interest rate		4.03 % - 4.39%		3.93% - 4.35%
Expected dividend yield		—		—
Exercise price	$	2.38 - $7.60	$	14.88 - $19.20

A summary of the status of the Company’s nonvested restricted common stock awards at December 31, 2025 and changes during the year ended December 31, 2025 was as follows:


Restricted Stock Awards	Shares			Weighted- Average Grant Date Fair Value Per Share
Nonvested restricted common stock awards at December 31, 2024		2,687		$	31.76
Granted		—		$	—
Vested		(2,687	)	$	31.76
Forfeited		—		$	—

Nonvested restricted common stock awards at December 31, 2025		—		$	—

As of December 31, 2025, there was no unrecognized share-based compensation expense related to nonvested restricted common stock awards.

A summary of the status of the Company’s nonvested restricted common stock units at December 31, 2025 and changes during the year ended December 31, 2025 was as follows:


Restricted Stock Units	Shares			Weighted- Average Grant Date Fair Value Per Share
Nonvested restricted common stock units at December 31, 2024		133,069		$	18.89
Granted		59,500		$	5.96
Forfeited		(66,646	)	$	12.34
Vested		(87,320	)	$	19.18

Nonvested restricted common stock units at December 31, 2025		38,603		$	9.60

As of December 31, 2025, there was unrecognized share-based compensation expense related to nonvested restricted common stock units of $0.3 million, which the Company expects to recognize over a weighted-average period of approximately 2.4 years.

2021 Employee Stock Purchase Plan

future issuances under this plan. The share pool will automatically increase on January 1st of each year from 2022 to 2031 by the lesser of (i) one percent of the number of shares of the Company’s common stock outstanding as of such date (ii) 72,831 shares of the Company’s common stock, and (iii) the number of shares of the Company’s common stock determined by the board of directors on or prior to such date. The 2021 ESPP share pool did not increase on January 1, 2025 or January 1, 2024. As of December 31, 2025, the total number of shares of the Company’s common stock available for future issuance under the 2021 ESPP was 94,281 shares. During the years ended December 31, 2025 and 2024, the Company issued 7,258 and 7,603 shares, respectively, of the Company’s common stock under the 2021 ESPP.

The 2021 ESPP allows eligible participants to purchase shares of the Company’s common stock through authorized payroll deductions. The purchase price of the shares will not be less than 85% of the lower of the fair market value the Company’s common stock on the first day of an offering or on the date of the purchase.

For the years ended December 31, 2025 and 2024, the total share-based compensation for the 2021 ESPP was $16 thousand and $0.1 million, respectively.

- Definition

The entire disclosure for equity.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-8A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 505
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478448/946-505-50-6

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-6

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480008/505-10-S99-1

Reference 10: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 505
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/505/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-13

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-14

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 16
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-16

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 505
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481112/505-10-50-18

+ Details

MARKETABLE SECURITIES

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Investments, Debt and Equity Securities [Abstract]

MARKETABLE SECURITIES

3. MARKETABLE SECURITIES

The amortized cost, gross unrealized

holding

gains, gross unrealized holding losses and fair value of our marketable securities by type of security as of March 31, 2026 and December 31, 2025 was as follows:


			MARCH 31, 2026
(in thousands)	Fair Value Hierarchy Level		Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Cash and cash equivalents		Level 1	$	16,383	$	—	$	—	$	16,383
U.S. treasury securities		Level 1		5,495		1		—		5,496

			$	21,878	$	1	$	—	$	21,879


			DECEMBER 31, 2025
(in thousands)	Fair Value Hierarchy Level		Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Cash and cash equivalents		Level 1	$	6,695	$	—	$	—	$	6,695
U.S. treasury securities		Level 1		19,212		17		—		19,229
U.S. government agency securities		Level 2		4,630		1		—		4,631

			$	30,537	$	18	$	—	$	30,555

The fair values of marketable securities by classification in the condensed consolidated balance sheets as of March 31, 2026 and December 31, 2025 was as follows:


(in thousands)	MARCH 31, 2026		DECEMBER 31, 2025
Cash and cash equivalents	$	16,383	$	7,193
Marketable securities		5,496		23,362

	$	21,879	$	30,555

The fair values of

available-for-sale

debt securities as of March 31, 2026 and December 31, 2025, by contractual maturity, are summarized as follows:


(in thousands)	MARCH 31, 2026		DECEMBER 31, 2025
Due in one year or less	$	21,879	$	30,555
Due after one year through two years		—		—

	$	21,879	$	30,555

The aggregate fair value of

available-for-sale

debt securities in an unrealized loss position as of December 31, 2025 was $0.7 million. There was no aggregate fair value of

available-for-sale

debt securities in an unrealized loss position as of March 31, 2026. As of March 31, 2026, the Company did

not

have any investments in a continuous unrealized loss position for more than twelve months. As of March 31, 2026, the Company believes that the cost basis of its

available-for-sale

debt securities is recoverable. No allowance for credit loss was recorded as of March 31, 2026 and December 31, 2025.

4. MARKETABLE SECURITIES

The amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of our marketable securities by type of security as of December 31, 2025 and 2024 was as follows:


			DECEMBER 31, 2025
(in thousands)	Fair Value Hierarchy Level		Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Cash and cash equivalents		Level 1	$	6,695	$	—	$	—	$	6,695
U.S. treasury securities		Level 1		19,212		17		—		19,229
U.S. government agency securities		Level 2		4,630		1		—		4,631

			$	30,537	$	18	$	—	$	30,555


			DECEMBER 31, 2024
(in thousands)	Fair Value Hierarchy Level		Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Money market funds		Level 1	$	8,705	$	—	$	—		$	8,705
U.S. treasury securities		Level 1		34,316		54		(15	)		34,355
U.S. government agency securities		Level 2		17,224		32		(3	)		17,253

			$	60,245	$	86	$	(18	)	$	60,313

The fair values of marketable securities by classification on the consolidated balance sheets as of December 31, 2025 and 2024 was as follows:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Cash and cash equivalents	$	7,193	$	8,705
Marketable securities		23,362		51,608

	$	30,555	$	60,313

The fair values of

available-for-sale

debt securities as of December 31, 2025 and 2024, by contractual maturity, are summarized as follows:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Due in one year or less	$	30,555	$	51,357
Due after one year through two years		—		8,956

	$	30,555	$	60,313

The aggregate fair value of

available-for-sale

debt securities in an unrealized loss position as of December 31, 2025 and 2024 was $0.7 million and $10.4 million, respectively. As of December 31, 2025 and 2024, we did not have any investments in a continuous unrealized loss position for more than twelve months. As of December 31, 2025, the Company believes that the cost basis of our

available-for-sale

debt securities is recoverable. No allowance for credit losses was recorded as of December 31, 2025 and 2024.

SUBSEQUENT EVENTS	3 Months Ended	12 Months Ended
SUBSEQUENT EVENTS	Mar. 31, 2026	Dec. 31, 2025
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	12. SUBSEQUENT EVENTS On March 1, 2026, Rallybio entered into an Agreement and Plan of Merger and Reorganization with Candid pursuant to which the parties intended to undertake a business combination. On May 3, 2026, Candid terminated the Merger Agreement concurrently with entering into a Permitted Alternative Agreement (as defined in the Merger Agreement) with UCB. As a result of the termination of the Merger Agreement, Rallybio was paid on May 4, 2026 a $50.0 million Parent Termination Fee (as defined in the Merger Agreement ) and was reimbursed $0.4 million for certain expenses. On April 9, 2026, the J&J Collaboration Agreement terminated upon completion of the initial term of the agreement.	14. SUBSEQUENT EVENTS Share Price and Reverse Split On February 24, 2025, the Company received a notification letter from The Nasdaq Stock Market LLC (“Nasdaq”) Listing Qualifications Department notifying the Company that the closing bid price of the Company’s shares of common stock was below the minimum closing bid price of $1.00 per share during the prior 30 consecutive business days (the “Notice”), as required for continued listing on the Nasdaq. Pursuant to Nasdaq’s Listing Rules, the Company had until August 25, 2025 (the “Initial Compliance Date”) to regain compliance with the minimum closing bid price requirement. As of the Initial Compliance Date, the Company had not regained compliance with the minimum closing bid price requirement. On August 26, 2025, Nasdaq notified the Company that it had approved the Company’s application to transfer its listing to the Nasdaq Capital Market and that the Company is eligible for an additional 180 calendar day period, or until February 23, 2026 (the “Second Compliance Date”), to regain compliance with the minimum closing bid price requirement. At the opening of business on August 29, 2025, the Company’s common stock was transferred to the Nasdaq Capital Market, which operates in substantially the same manner as the Nasdaq Global Select Market, where it will continue to trade under the symbol “RLYB.” On January 26, 2026, the Company’s stockholders approved a proposal to amend its Amended and Restated Certificate of Incorporation (the “Certificate of Incorporation”) with the Secretary of State of the State of Delaware to effect a reverse stock split of the Company’s issued and outstanding common stock, par value $0.0001 at a ratio of 1-for-8. Pursuant to the Certificate of Amendment, the Reverse Stock Split became effective at 12:01 a.m., Eastern Time, on February 6, 2026 and began trading on a post-split basis under CUSIP number 75120L 209. All common share, per share and related information included in the accompanying financial statements and footnote disclosures have been adjusted retroactively, where applicable, to reflect the Reverse Stock Split. On February 24, 2026, Rallybio received a letter from Nasdaq notifying the Company it had regained compliance with the Nasdaq’s Listing Rules and that it complies with the requirements for continued listing. Proposed Merger with Candid Therapeutics On March 1, 2026, Rallybio entered into the Merger Agreement with Candid, a clinical-stage biotechnology company advancing a leading portfolio of TCE therapeutics for autoimmune diseases, and the Merger Sub. Upon the terms and subject to the satisfaction of the conditions described in the Merger Agreement, Merger Sub will be merged with and into Candid, with Candid surviving as a wholly owned subsidiary of the Merger. The Merger is intended to qualify as a tax-free reorganization for U.S. federal income tax purposes. Subject to the terms and conditions of the Merger Agreement, at the Effective Time, (a) each then-outstanding share of common stock or preferred stock of Candid Share (excluding any share described in clauses (b) or (c) below and Candid Shares held by stockholders who have exercised and perfected appraisal rights for such shares) will be converted into the right to receive a number of shares of Rallybio Common Stock, par value $0.0001 per share, calculated in accordance with the Exchange Ratio, (b) each Candid Share issued in the Concurrent Financing will be converted into the right to receive a number of shares of Rallybio Common Stock calculated in accordance with the Concurrent Financing Exchange Ratio, (c) any Candid Shares held as treasury shares or held or owned by Rallybio, Merger Sub or any subsidiary of Rallybio or Candid immediately prior to the Effective Time will be canceled and shall cease to exist, and no consideration shall be delivered in exchange therefor. Each then-outstanding option to purchase Candid Shares will be converted into an option to purchase Rallybio Common Stock, subject to adjustment as set forth in the Merger Agreement. Concurrently with the execution and delivery of the Merger Agreement, certain investors entered into a subscription agreement with Candid, pursuant to which such investors have agreed to purchase, immediately prior to the Merger, shares of Candid common stock representing an aggregate commitment of approximately $505.5 million in the Concurrent Financing. The shares of Candid common stock that are issued in the Concurrent Financing will be or will have the right to be, respectively, converted into shares of Rallybio common stock in the Merger. Under the Exchange Ratio and Concurrent Financing Exchange Ratio formulas in the Merger Agreement, immediately after the Closing, on a pro forma basis and based upon the number of shares of Rallybio Common Stock expected to be issued in connection with the Merger , pre-Merger equityholders of Candid (other than investors in the Concurrent Financing) are expected to own approximately 57.55% of the combined company, pre-Merger equityholders of Rallybio are expected to own approximately 3.65% of the combined company and the Investors in the Concurrent Financing are expected to own approximately 38.80% of the combined company (assuming proceeds from the Concurrent Financing of $505.5 million), in each case, calculated on a fully diluted basis, using the treasury stock method, and subject to certain assumptions, including (i) a valuation for Rallybio of $47.5 million (assuming Rallybio has net cash (“Rallybio Net Cash”) of $37.5 million as of the closing of the Merger (the “Closing” and such date, the “Closing Date”)), (ii) a fixed valuation for Candid of $750.0 million, and (iii) the relative capitalization of Rallybio and Candid. The percentage of the combined company that each party’s equity holders will own following the Closing is subject to certain adjustments as described in the Merger Agreement, including the amount of the final Rallybio Net Cash at Closing. Immediately prior to the Effective Time, Rallybio and a rights agent are expected to enter into the CVR Agreement, pursuant to which holders of record of certain Rallybio securities as of the close of business on the last business day prior to the day on which the Effective Time occurs will receive one contingent value right (each, a “CVR”) for each outstanding share of Rallybio Common Stock, prefunded warrant, Rallybio restricted stock unit or In the Money Parent Option (as defined in the CVR Agreement) held as of such date. Pursuant to the CVR Agreement, each CVR holder will be entitled to receive their pro rata share of (i) all of the net proceeds (including cash the value of stock to the extent listed on a national exchange, at the time of disposition), if any, received by Rallybio as a result of payments made to Rallybio of any upfront, milestone, royalty and other payments received under any disposition agreement related to Rallybio’s Legacy Assets, and (ii) all of the cash proceeds, if any, received from Recursion under the Membership Interest Purchase Agreement, dated July 8, 2025, by and among Recursion, Exscientia Ventures I, Inc., Rallybio Corporation and Rallybio IPB, LLC. For a period of one year after the Closing Date, Rallybio will use commercially reasonable efforts to effect the disposition of the Legacy Assets. Such net proceeds will be subject to certain permitted deductions, including for applicable tax payments, certain expenses incurred or other liabilities borne by Rallybio or its affiliates in respect of the Legacy Assets, and losses incurred by Rallybio or its affiliates due to a third-party proceeding in connection with such disposition.

NET LOSS PER COMMON SHARE - Additional Information (Details) - shares	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024	Nov. 30, 2022
Stock Options and Nonvested Restricted Share
Antidilutive Units
Antidilutive securities excluded from computation of earnings per share, amount (in shares)	700,000	900,000	700,000	700,000
Pre-Funded Warrants \| Follow-on Offering
Antidilutive Units
Number of securities called by warrants or rights (in shares)		416,673			416,673

MARKETABLE SECURITIES - Schedule of Fair Value of Marketable Securities by Type of Security (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	$ 21,878	$ 30,537	$ 60,245
Gross Unrealized Holding Gains	1	18	86
Gross Unrealized Holding Losses	0	0	(18)
Fair Value	21,879	30,555	60,313
Level 1 \| Cash and cash equivalents
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	16,383	6,695
Gross Unrealized Holding Gains	0	0
Gross Unrealized Holding Losses	0	0
Fair Value	16,383	6,695
Level 1 \| U.S. treasury securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost	5,495	19,212	34,316
Gross Unrealized Holding Gains	1	17	54
Gross Unrealized Holding Losses	0	0	(15)
Fair Value	$ 5,496	19,229	34,355
Level 1 \| Money market funds
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost			8,705
Gross Unrealized Holding Gains			0
Gross Unrealized Holding Losses			0
Fair Value			8,705
Level 2 \| U.S. government agency securities
Debt Securities, Available-for-Sale [Line Items]
Amortized Cost		4,630	17,224
Gross Unrealized Holding Gains		1	32
Gross Unrealized Holding Losses		0	(3)
Fair Value		$ 4,631	$ 17,253

RESTRUCTURING AND SEVERANCE (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Restructuring and Related Activities [Abstract]

Schedule of Restructuring and Related Costs

The following table summarizes the restructuring accrual activity as of March 31, 2026:


(in thousands)	MARCH 31, 2026
Beginning accrued severance as of January 1, 2026	$	523
Severance incurred during the period		2,302
Severance paid and adjustments made during the period		(1,449	)

Ending accrued severance as of March 31, 2026	$	1,376

The following table summarizes the restructuring accrued expense activity as of December 31, 2025:


(in thousands)	DECEMBER 31, 2025
Beginning accrued severance	$	203
Severance incurred during the period		1,706
Severance paid and adjustments made during the period		(1,386	)

Ending accrued severance	$	523

NET LOSS PER COMMON SHARE - Summary of Basic and diluted loss per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Earnings Per Share [Abstract]
Net loss	$ (8,278)	$ (9,439)	$ (8,978)	$ (57,775)
Weighted-average number of common shares outstanding, basic (in shares)	5,688,584	5,597,528	5,629,370	5,443,332
Weighted-average number of common shares outstanding, diluted (in shares)	5,688,584	5,597,528	5,629,370	5,443,332
Net loss per common share, basic (in dollars per share)	$ (1.46)	$ (1.69)	$ (1.59)	$ (10.61)
Net loss per common share, diluted (in dollars per share)	$ (1.46)	$ (1.69)	$ (1.59)	$ (10.61)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 105
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 52
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-52

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-15

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-7

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-10

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-7

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 105
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 52
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-52

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-15

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-7

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-7

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

+ Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

BUSINESS AND LIQUIDITY	3 Months Ended	12 Months Ended
BUSINESS AND LIQUIDITY	Mar. 31, 2026	Dec. 31, 2025
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BUSINESS AND LIQUIDITY	1. BUSINESS AND LIQUIDITY Rallybio Corporation and subsidiaries (“Rallybio”, the “Company”, “we”, “our”, or “us”) is a clinical-stage biotechnology company comprised of experienced biopharma industry leaders with extensive research, development, and rare disease expertise with a mission to develop and commercialize life-transforming therapies for patients with severe and rare diseases. The Company’s lead program, RLYB116, is a differentiated complement component 5 (“C5”) inhibitor with the potential to treat diseases of complement dysregulation. In addition, RLYB332, a long-acting matriptase-2 (“MTP-2”) antibody for the treatment of diseases of iron overload is currently in preclinical development. In 2025, the Company completed a confirmatory pharmacokinetic (“PK”) and pharmacodynamic (“PD”) study of RLYB116 in healthy volunteers and reported data in the first quarter of 2026. In April 2025, the Company announced the discontinuation of its RLYB212 program for the prevention of fetal and neonatal alloimmune thrombocytopenia (“FNAIT”) based on PK data from the Phase 2 clinical trial that demonstrated an inability of the RLYB212 dose regimen to achieve predicted target concentrations, as well as the minimum target concentration required for efficacy. In July 2025, the Company entered into a definitive agreement to sell its interest in REV102, an Ectonucleotide Pyrophosphatase/Phosphodiesterase 1 (“ENPP1”) inhibitor in preclinical development for the treatment of patients with hypophosphatasia (“HPP”), to a subsidiary of its joint venture partner Recursion Pharmaceuticals, Inc. (“Recursion”) (the “JV Sale”). On March 1, 2026, Rallybio entered into an Agreement and Plan of Merger and Reorganization with Candid Therapeutics, Inc. (“Candid”) (the “Merger Agreement”) pursuant to which the parties intended to undertake a business combination (the “Merger”). On May 3, 2026, Candid terminated the Merger Agreement concurrently with entering into a Permitted Alternative Agreement (as defined in the Merger Agreement) with UCB S.A. (“UCB”). As a result of the termination of the Merger Agreement, Rallybio was paid on May 4, 2026 a $50.0 million Parent Termination Fee (as defined in the Merger Agreement) and was reimbursed $0.4 million for certain expenses. The Company had cash, cash equivalents and marketable securities of $46.8 million as of March 31, 2026. The Company currently expects that its cash, cash equivalents and marketable securities will be sufficient to fund its operating expenses and capital requirements for more than 12 months from the date these unaudited condensed consolidated financial statements are issued. However, the Company does not anticipate that its current cash, cash equivalents and marketable securities as of March 31, 2026 will be sufficient to fund any of its product candidates through regulatory approval, and it will need to raise substantial additional capital to complete the development and commercialization of its product candidates, if approved. Rallybio may satisfy its future cash needs through the sale of equity securities, debt financings, corporate collaborations or license agreements, working capital lines of credit, grant funding, interest income earned on invested cash balances or a combination of one or more of these sources.	1. BUSINESS Rallybio Corporation and subsidiaries (“Rallybio”, the “Company”, “we”, “our”, or “us”) is a clinical-stage biotechnology company comprised of experienced biopharma industry leaders with extensive research, development, and rare disease expertise with a mission to develop and commercialize life-transforming therapies for patients with severe and rare diseases. The Company’s lead program, RLYB116, is a differentiated complement component 5 (“C5”) inhibitor with the potential to treat diseases of complement dysregulation. In addition, RLYB332, a long-acting matriptase-2 (“MTP-2”) antibody for the treatment of diseases of iron overload is currently in preclinical development. In 2025, the Company completed a confirmatory pharmacokinetic (“PK”) and pharmacodynamic (“PD”) study of RLYB116 in healthy volunteers and reported data in the first quarter of 2026. In April 2025, the Company announced the discontinuation of its RLYB212 program for the prevention of fetal and neonatal alloimmune thrombocytopenia (“FNAIT”) based on PK data from the Phase 2 clinical trial that demonstrated an inability of the RLYB212 dose regimen to achieve predicted target concentrations, as well as the minimum target concentration required for efficacy. In July 2025, the Company entered into a definitive agreement to sell its interest in REV102, an Ectonucleotide Pyrophosphatase/Phosphodiesterase 1 (“ENPP1”) inhibitor in preclinical development for the treatment of patients with hypophosphatasia (“HPP”), to a subsidiary of its joint venture partner Recursion Pharmaceuticals, Inc. (“Recursion”) (the “JV Sale”). On March 1, 2026, Rallybio entered into an Agreement and Plan of Merger and Reorganization (the “Merger Agreement”) with Candid Therapeutics, Inc., a Delaware corporation (“Candid”), a clinical-stage biotechnology company advancing a leading portfolio of T-cell engager (“TCE”) therapeutics for autoimmune diseases, and Farmington Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of Rallybio (“Merger Sub”). Upon the terms and subject to the satisfaction of the conditions described in the Merger Agreement, Merger Sub will be merged with and into Candid, with Candid surviving as a wholly owned subsidiary of Rallybio (the “Merger” and, together with all of the other transactions contemplated by the Merger, the “Contemplated Transactions”). The Merger is intended to qualify as a tax-free reorganization for U.S. federal income tax purposes. Concurrently with the execution and delivery of the Merger Agreement, certain investors entered into a subscription agreement with Candid, pursuant to which such investors have agreed to purchase, immediately prior to the Merger, shares of Candid common stock representing an aggregate commitment of approximately $505.5 million in the concurrent financing (the “Concurrent Financing”). The shares of Candid common stock that are issued in the Concurrent Financing will be or will have the right to be, respectively, converted into shares of Rallybio common stock, par value $0.0001 per share (“Rallybio Common Stock”), in the Merger. Subject to the terms and conditions of the Merger Agreement, at the effective time of the Merger (the “Effective Time”), (a) each then-outstanding share of common stock or preferred stock of Candid (each such share, a “Candid Share”) (excluding any share described in clauses (b) or (c) below and Candid Shares held by stockholders who have exercised and perfected appraisal rights for such shares) will be converted into the right to receive a number of shares of Rallybio Common Stock calculated in accordance with the Exchange Ratio as set forth in the Merger Agreement (the “Exchange Ratio”), (b) each Candid Share issued in the Concurrent Financing will be converted into the right to receive a number of shares of Rallybio Common Stock calculated in accordance with the Concurrent Financing Exchange Ratio as set forth in the Merger Agreement (the “Concurrent Financing Exchange Ratio”), (c) any Candid Shares held as treasury shares or held or owned by Rallybio, Merger Sub or any subsidiary of Rallybio or Candid immediately prior to the Effective Time will be canceled and shall cease to exist, and no consideration shall be delivered in exchange therefor. Each then-outstanding option to purchase Candid Shares will be converted into an option to purchase Rallybio Common Stock, subject to adjustment as set forth in the Merger Agreement. Under the Exchange Ratio and Concurrent Financing Exchange Ratio formulas in the Merger Agreement, immediately after the Closing, on a pro forma basis and based upon the number of shares of Rallybio Common Stock expected to be issued in connection with the Merger , pre-Merger equityholders of Candid (other than investors in the Concurrent Financing) are expected to own approximately 57.55% of the combined company, pre-Merger equityholders of Rallybio are expected to own approximately 3.65% of the combined company and the Investors in the Concurrent Financing are expected to own approximately 38.80% of the combined company (assuming proceeds from the Concurrent Financing of $505.5 million), in each case, calculated on a fully diluted basis, using the treasury stock method, and subject to certain assumptions, including (i) a valuation for Rallybio of $47.5 million (assuming Rallybio has net cash (“Rallybio Net Cash”) of $37.5 million as of the closing of the Merger (the “Closing” and such date, the “Closing Date”)), (ii) a fixed valuation for Candid of $750.0 million, and (iii) the relative capitalization of Rallybio and Candid. The percentage of the combined company that each party’s equity holders will own following the Closing is subject to certain adjustments as described in the Merger Agreement, including the amount of the final Rallybio Net Cash at Closing. Immediately prior to the Effective Time, Rallybio and a rights agent are expected to enter into a Contingent Value Rights Agreement (the “CVR Agreement”), pursuant to which holders of record of certain Rallybio securities as of the close of business on the last business day prior to the day on which the Effective Time occurs will receive one contingent value right (each, a “CVR”) for each outstanding share of Rallybio Common Stock, prefunded warrant, Rallybio restricted stock unit or In the Money Parent Option (as defined in the CVR Agreement) held as of such date. Pursuant to the CVR Agreement, each CVR holder will be entitled to receive their pro rata share of (i) all of the net proceeds (including cash the value of stock to the extent listed on a national exchange, at the time of disposition), if any, received by Rallybio as a result of payments made to Rallybio of any upfront, milestone, royalty and other payments received under any disposition agreement related to Rallybio’s pre-Merger assets (the “Legacy Assets”), and (ii) all of the cash proceeds, if any, received from Recursion under the Membership Interest Purchase Agreement, dated July 8, 2025, by and among Recursion, Exscientia Ventures I, Inc., Rallybio Corporation and Rallybio IPB, LLC. For a period of one year after the Closing Date, Rallybio will use commercially reasonable efforts to effect the disposition of the Legacy Assets. Such net proceeds will be subject to certain permitted deductions, including for applicable tax payments, certain expenses incurred or other liabilities borne by Rallybio or its affiliates in respect of the Legacy Assets, and losses incurred by Rallybio or its affiliates due to a third-party proceeding in connection with such disposition.

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Revenue:
Total revenue	$ 212	$ 212	$ 858	$ 636
Operating expenses:
Research and development	2,871	5,725	19,597	41,507
General and administrative	6,074	4,157	14,325	19,625
Total operating expenses	8,945	9,882	33,922	61,132
Loss from operations	(8,733)	(9,670)	(33,064)	(60,496)
Other income:
Interest income	201	644	2,189	4,216
Gain on sale of joint venture and other income	254	174	22,771	744
Total other income, net	455	818	24,960	4,960
Loss before equity in losses of joint venture	(8,278)	(8,852)	(8,104)	(55,536)
Loss on investment in joint venture	0	587	874	2,239
Net loss	$ (8,278)	$ (9,439)	$ (8,978)	$ (57,775)
Net loss per common share, basic (in dollars per share)	$ (1.46)	$ (1.69)	$ (1.59)	$ (10.61)
Net loss per common share, diluted (in dollars per share)	$ (1.46)	$ (1.69)	$ (1.59)	$ (10.61)
Weighted-average common shares outstanding, basic (in shares)	5,688,584	5,597,528	5,629,370	5,443,332
Weighted-average common shares outstanding, diluted (in shares)	5,688,584	5,597,528	5,629,370	5,443,332
Other comprehensive (loss) gain:
Net unrealized (loss) gain on marketable securities	$ (17)	$ (21)	$ (50)	$ 53
Other comprehensive (loss) gain	(17)	(21)	(50)	53
Comprehensive loss	(8,295)	(9,460)	(9,028)	(57,722)
Collaboration and license revenue
Revenue:
Total revenue	$ 212	$ 212	$ 858	$ 636

Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Statement of Financial Position [Abstract]
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	200,000,000	200,000,000	200,000,000
Common stock, shares issued (in shares)	5,290,236	5,283,321	5,188,743
Common stock, shares outstanding (in shares)	5,290,236	5,283,321	5,188,743
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001	$ 0.0001
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000	50,000,000
Preferred stock, shares issued (in shares)	0	0	0
Preferred stock, shares outstanding (in shares)	0	0	0

Fees Summary	Jul. 15, 2026 USD ($)
Fees Summary [Line Items]
Total Offering	$ 6,582.81
Previously Paid Amount	0.00
Total Fee Amount	0.91
Total Offset Amount	0.00
Net Fee	$ 0.91
Offering Table N/A
Offset Table N/A	N/A
Combined Prospectus Table N/A	N/A

BALANCE SHEET COMPONENTS (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Balance Sheet Related Disclosures [Abstract]

Schedule of Prepaid Expenses and Other Assets

Prepaid expenses and other current assets consisted of the following as of March 31, 2026 and December 31, 2025:


(in thousands)	MARCH 31, 2026		DECEMBER 31, 2025
Research and development	$	595	$	3,372
Insurance		231		409
Other prepaids		135		219
Other current assets		5,734		2,517

	$	6,695	$	6,517

Prepaid expenses and other assets consisted of the following as of December 31, 2025 and 2024:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Research and development	$	3,372	$	697
Insurance		409		424
Other prepaids		219		214
Other current assets		2,517		995

	$	6,517	$	2,330

Schedule of Accrued Expenses

Accrued expenses consisted of the following as of March 31, 2026 and December 31, 2025:


(in thousands)	MARCH 31, 2026		DECEMBER 31, 2025
Compensation and related expenses	$	1,407	$	2,334
Professional fees		1,396		1,039
Research and development		94		394
Other accrued expenses		204		24

	$	3,101	$	3,791

Accrued expenses consisted of the following as of December 31, 2025 and 2024:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Research and development	$	394	$	1,197
Compensation and related expenses		2,334		3,095
Professional fees		1,039		510
Other		24		160

	$	3,791	$	4,962

Schedule of Property and Equipment, Net

Property and equipment consisted of the following as of December 31, 2025 and 2024:


(in thousands)	DECEMBER 31, 2025			DECEMBER 31, 2024
Computer and other equipment	$	191		$	191
Capitalized software		89			89
Furniture and fixtures		76			151
Leasehold improvements		147			338

Total property and equipment		503			769
Less: accumulated depreciation		(480	)		(654	)

Total property and equipment—net	$	23		$	115

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION (Tables)

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Schedule of Property and Equipment Estimated Useful Lives

The estimated useful life for each major asset classification are as follows:


Asset Classification		Estimated Useful Life
Computer and other equipment		3 years
Capitalized software		3 years
Furniture and fixtures		6 years
Leasehold improvements		lesser of lease life or useful life

NET LOSS PER COMMON SHARE

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Earnings Per Share [Abstract]

NET LOSS PER COMMON SHARE

8. NET LOSS PER COMMON SHARE

Basic and diluted net loss per common share for the three months ended March 31, 2026 and 2025 was calculated as follows:


	FOR THE THREE MONTHS ENDED MARCH 31,
(in thousands except share and per share amounts)	2026			2025
Net loss	$	(8,278	)	$	(9,439	)
Weighted-average number of common shares outstanding, basic and diluted		5,688,584			5,597,528
Net loss per common share, basic and diluted	$	(1.46	)	$	(1.69	)

Basic net loss per share of common stock is based on the weighted-average number of shares of common stock outstanding during the period.

Pre-funded

warrants to purchase 416,673 shares of common stock that were issued in connection with the November 2022

follow-on

offering are included in the weighted-average number of common shares outstanding for the three months ended March 31, 2026 and 2025. The weighted- average number of common shares outstanding diluted for the three months ended March 31, 2026 and 2025 excluded approximately 0.7 million and 0.9 million stock options and nonvested restricted stock awards and units, respectively, which were not

dilutive

11. NET LOSS PER COMMON SHARE

Basic and diluted loss per common share were calculated as follows:


	FOR THE YEAR ENDED DECEMBER 31,
(in thousands except share and per share amounts)	2025			2024
Net loss	$	(8,978	)	$	(57,775	)
Weighted-average number of common shares outstanding, basic and diluted		5,629,370			5,443,332

Net loss per common share, basic and diluted	$	(1.59	)	$	(10.61	)

Basic net loss per share of common stock is based on the weighted-average number of shares of common stock outstanding during the period.

Pre-funded

warrants to purchase 416,673 shares of common stock that were issued in connection with the November 2022

follow-on

offering were included in the weighted-average number of common shares outstanding for the years ended December 31, 2025 and 2024, respectively. The weighted-average number of common shares outstanding diluted for the years ended December 31, 2025 and 2024 both exclude approximately $0.7 million stock options and nonvested restricted stock awards and units, which were not dilutive.

MARKETABLE SECURITIES (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Investments, Debt and Equity Securities [Abstract]

Schedule of Fair Value of Marketable Securities by Type of Security

The amortized cost, gross unrealized

holding

gains, gross unrealized holding losses and fair value of our marketable securities by type of security as of March 31, 2026 and December 31, 2025 was as follows:


			MARCH 31, 2026
(in thousands)	Fair Value Hierarchy Level		Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Cash and cash equivalents		Level 1	$	16,383	$	—	$	—	$	16,383
U.S. treasury securities		Level 1		5,495		1		—		5,496

			$	21,878	$	1	$	—	$	21,879


			DECEMBER 31, 2025
(in thousands)	Fair Value Hierarchy Level		Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Cash and cash equivalents		Level 1	$	6,695	$	—	$	—	$	6,695
U.S. treasury securities		Level 1		19,212		17		—		19,229
U.S. government agency securities		Level 2		4,630		1		—		4,631

			$	30,537	$	18	$	—	$	30,555

The amortized cost, gross unrealized holding gains, gross unrealized holding losses and fair value of our marketable securities by type of security as of December 31, 2025 and 2024 was as follows:


			DECEMBER 31, 2025
(in thousands)	Fair Value Hierarchy Level		Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
Cash and cash equivalents		Level 1	$	6,695	$	—	$	—	$	6,695
U.S. treasury securities		Level 1		19,212		17		—		19,229
U.S. government agency securities		Level 2		4,630		1		—		4,631

			$	30,537	$	18	$	—	$	30,555


			DECEMBER 31, 2024
(in thousands)	Fair Value Hierarchy Level		Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses			Fair Value
Money market funds		Level 1	$	8,705	$	—	$	—		$	8,705
U.S. treasury securities		Level 1		34,316		54		(15	)		34,355
U.S. government agency securities		Level 2		17,224		32		(3	)		17,253

			$	60,245	$	86	$	(18	)	$	60,313

Schedule of Marketable Securities by Balance Sheet Location Classification

The fair values of marketable securities by classification in the condensed consolidated balance sheets as of March 31, 2026 and December 31, 2025 was as follows:


(in thousands)	MARCH 31, 2026		DECEMBER 31, 2025
Cash and cash equivalents	$	16,383	$	7,193
Marketable securities		5,496		23,362

	$	21,879	$	30,555

The fair values of marketable securities by classification on the consolidated balance sheets as of December 31, 2025 and 2024 was as follows:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Cash and cash equivalents	$	7,193	$	8,705
Marketable securities		23,362		51,608

	$	30,555	$	60,313

Schedule of Fair Values of Available-for-Sale Debt Securities by Contractual Maturity

The fair values of

available-for-sale

debt securities as of March 31, 2026 and December 31, 2025, by contractual maturity, are summarized as follows:


(in thousands)	MARCH 31, 2026		DECEMBER 31, 2025
Due in one year or less	$	21,879	$	30,555
Due after one year through two years		—		—

	$	21,879	$	30,555

The fair values of

available-for-sale

debt securities as of December 31, 2025 and 2024, by contractual maturity, are summarized as follows:


(in thousands)	DECEMBER 31, 2025		DECEMBER 31, 2024
Due in one year or less	$	30,555	$	51,357
Due after one year through two years		—		8,956

	$	30,555	$	60,313

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Dec. 31, 2024
Current assets:
Cash and cash equivalents	$ 41,299	$ 31,374	$ 13,903
Marketable securities	5,496	23,362	51,608
Prepaid expenses and other current assets	6,695	6,517	2,330
Total current assets	53,490	61,253	67,841
Property and equipment, net	20	23	115
Operating lease right-of-use assets	152	175	152
Other assets, noncurrent	810	810	0
Total assets	54,472	62,261	68,108
Current liabilities:
Accounts payable	940	126	278
Accrued expenses	3,101	3,791	4,962
Operating lease liabilities	99	94	154
Deferred revenue	0	212	848
Total current liabilities	4,140	4,223	6,242
Operating lease liabilities, noncurrent	55	82	0
Deferred revenue, noncurrent		0	212
Total liabilities	4,195	4,305	6,454
Commitments and contingencies (Note 7)
Stockholders' equity
Common stock, $0.0001 par value per share; 200,000,000 shares authorized as of March 31, 2026 and December 31, 2025; and 5,290,236 and 5,283,321 shares issued and outstanding as of March 31, 2026 and December 31, 2025, respectively	4	4	4
Preferred stock, $0.0001 par value per share; 50,000,000 shares authorized as of March 31, 2026 and December 31, 2025; no shares issued or outstanding as of March 31, 2026 and December 31, 2025	0	0	0
Additional paid-in capital	360,548	359,932	354,602
Accumulated other comprehensive gain	1	18	68
Accumulated deficit	(310,276)	(301,998)	(293,020)
Total stockholders' equity	50,277	57,956	61,654
Total liabilities and stockholders' equity	$ 54,472	$ 62,261	$ 68,108

SEGMENTS (Tables)

3 Months Ended

12 Months Ended

Mar. 31, 2026

Dec. 31, 2025

Segment Reporting [Abstract]

Schedule of Segment Reporting Information, by Segment


	FOR THE THREE MONTHS ENDED MARCH 31,
(in thousands)	2026			2025
Revenue	$	212		$	212
Less:
Research and development:
RLYB212		56			2,438
RLYB116		396			619
Other program candidates		2			(163	)
Personnel expenses (including share-based compensation)		2,280			2,589
Other expenses		137			242
General and administrative, excluding personnel expenses		4,223			1,525
General and administrative, personnel expenses (including share-based compensation)		1,851			2,632
Other segment items*		(455	)		(231	)

Segment net loss	$	(8,278	)	$	(9,439	)

*	Other segment items include total other income, net and loss on investment in joint venture.


	FOR THE YEAR ENDED DECEMBER 31,
(in thousands)	2025			2024
Revenue	$	858		$	636
Less:
Research and development:
RLYB212		6,291			21,287
RLYB116		3,786			4,841
Other program candidates		(29	)		1,901
Personnel (including share-based compensation)		8,798			12,488
Other		751			990
General and administrative, excluding personnel		6,078			6,654
General and administrative, personnel (including share-based compensation)		8,247			12,971
Other segment items*		(24,086	)		(2,721	)

Segment net loss	$	(8,978	)	$	(57,775	)

Other segment items includes total other income, net and gain and loss on investment in joint venture.

INCOME TAXES - Schedule of Deferred Income Tax Benefits and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 50,322	$ 45,973
Intangible amortization	1,775	1,341
Section 174 capitalization	19,947	22,479
Research and development tax credits	25,701	24,047
Share-based compensation	2,405	2,654
Other	301	1,476
Gross deferred tax assets	100,451	97,970
Valuation allowance	(100,451)	(97,970)
Net deferred tax assets	$ 0	$ 0

COLLABORATION AND LICENSE AGREEMENTS	3 Months Ended	12 Months Ended
COLLABORATION AND LICENSE AGREEMENTS	Mar. 31, 2026	Dec. 31, 2025
License and collaboration agreements [Abstract]
COLLABORATION AND LICENSE AGREEMENTS	11. COLLABORATION AND LICENSE AGREEMENTS` In April 2024, the Company entered into a two-year collaboration agreement (the “J&J Collaboration Agreement”), with Johnson & Johnson (“J&J”) through its wholly-owned subsidiary, Momenta Pharmaceuticals, Inc. to facilitate the advancement of research into products to address unmet needs relating to FNAIT. In April 2025, the Company announced that RLYB212 Phase 2 PK results did not achieve target concentrations, including the minimum target concentration required for efficacy, and that the Company would discontinue its RLYB212 program for the prevention of FNAIT. Pursuant to the J&J Collaboration Agreement, the Company received an upfront payment of $0.5 million from J&J for the information dissemination and data provision services under the agreement. The J&J Collaboration Agreement provides that the Company is eligible for payments upon the achievement of certain screening-related events, however, the Company has discontinued screening and enrollment in both the FNAIT natural history study and the RLYB212 Phase 2 clinical trial. The Company evaluated the agreement and determined it was within the scope of ASC 606, Revenue Recognition (“ASC 606”). The Company determined there were performance obligations as follows: (1) Data collection and submission revenue – derived from Rallybio’s ongoing management of the studies including the maintenance of a minimum site footprint, the license to utilize, and timely, semi-annual submission of the anonymized data, in the required formats. (2) Dissemination of J&J materials & participant revenue – derived from Rallybio’s dissemination of content, information or materials related to the J&J-Sponsored Studies that are developed by J&J and are provided by Rallybio for the purpose of disseminating such content, information, or materials to staff at Rallybio study sites to provide to potential eligible participants regarding J&J’s independent study. In April 2024, the Company also entered into the JJDC Securities Purchase Agreement. Under the terms of the JJDC Securities Purchase Agreement, JJDC purchased 454,545 shares of the Company’s common stock with a par value of $0.0001 per share for a share purchase price of $14.56 per share which included a 10% premium on the then-current market price, for an aggregate purchase price of $6.6 million. The JJDC Securities Purchase Agreement contains provisions related to the registration of the shares and the restriction on the sale or transfer of the shares for a period of time. The Company determined the J&J Collaboration Agreement and the JJDC Securities Purchase Agreement represented combined agreements. In accordance with ASC 606 and ASC Topic 820, Fair Value Measurement, total consideration of $1.2 million for the shares of common stock from the JJDC Securities Purchase Agreement, which represents the premium of $0.7 million and discount for lack of marketability of $0.5 million, has been allocated to revenue and will be recognized over the two-year expected performance period. The Company valued the common stock issued to JJDC, in connection with the JJDC Securities Purchase Agreement at fair value. The resulting fair value of $5.4 million was determined by applying the discount due to lack of marketability during the registration and lock-up period to the public trading price of the common stock, which is a Level 1 input, on the date of sale. The Company determined the value of the lack of marketability during the registration and lock-up period by utilizing put option models, which are considered Level 3 inputs. Such option models included the Company’s historical volatility of 113.2% and the risk-free rate of 5.28% based on U.S. Treasury bond rates, as key inputs. The Company recognized revenue of $0.2 million for both the three months ended March 31, 2026 and 2025, related to data collection and data submission with the identified performance obligations, and the premium and discount allocated to revenue from the sale of the common stock to JJDC. As of March 31, 2026, all revenue was recognized due to the performance obligations being satisfied. On April 9, 2026, the J&J Collaboration Agreement terminated upon completion of the initial term of the agreement. The Company determined that the J&J Collaboration Agreement is not in the scope of ASC 808, Collaborative Arrangements .	3. COLLABORATION AND LICENSE AGREEMENTS Johnson & Johnson Collaboration In April 2024, the Company entered into a two-year collaboration agreement (the “J&J Collaboration Agreement”) with Johnson & Johnson, through its wholly owned subsidiary, Momenta Pharmaceuticals, Inc. (“J&J”) to facilitate the advancement of research into products to address unmet needs relating to FNAIT. In April 2025, the Company announced that RLYB212 Phase 2 PK results did not achieve target concentrations, including the minimum target concentration required for efficacy, and that the Company would discontinue its RLYB212 program for the prevention of FNAIT. The Company will continue to follow any previously screened Phase 2 participant who was also eligible to enroll in the multinational FNAIT natural history study, in accordance with the study’s protocol. Pursuant to the J&J Collaboration Agreement, the Company received an upfront payment of $0.5 million from J&J for the information dissemination and data provision services under the agreement. The J&J Collaboration Agreement provides that the Company is eligible for payments upon the achievement of certain screening-related events, however, the Company has discontinued screening and enrollment in both the FNAIT natural history study and the RLYB212 Phase 2 clinical trial. The Company evaluated the agreement and determined it was within the scope of ASC 606. The Company determined there were performance obligations as follows: (1) Data collection & submission revenue – derived from Rallybio’s ongoing management of the studies including the maintenance of a minimum site footprint, the license to utilize, and timely, semi-annual submission of the anonymized data, in the required formats. (2) Dissemination of J&J materials & participant revenue – derived from Rallybio’s dissemination of content, information or materials related to the J&J-Sponsored Studies that are developed by J&J and are provided by Rallybio for the purpose of disseminating such content, information, or materials to staff at Rallybio study sites to provide to potential eligible participants regarding J&J’s independent study. In April 2024, the Company also entered into a securities purchase agreement (the “JJDC Securities Purchase Agreement”) with Johnson & Johnson Innovation – JJDC, Inc. (“JJDC”). Under the terms of the JJDC Securities Purchase Agreement, JJDC made an equity investment purchasing 454,545 shares of common stock with a par value of $0.0001 per share for a share purchase price of $14.56 per share which includes a 10% premium for an aggregate purchase price of $6.6 million. The JJDC Securities Purchase Agreement contains provisions related to the registration of the shares and the restriction on the sale or transfer of the shares for a period of time. The Company determined the J&J Collaboration Agreement and the JJDC Securities Purchase Agreement represented combined agreements. In accordance with ASC 606 and ASC 820, total consideration of $1.2 million for the shares of common stock from the JJDC Securities Purchase Agreement, which represents the premium of $0.7 million and discount for lack of marketability of $0.5 million, has been allocated to revenue and will be recognized over the two year expected performance period. The Company valued the common stock issued to JJDC, in connection with the JJDC Securities Purchase Agreement at fair value. The resulting fair value of $5.4 million was determined by applying the discount due to lack of marketability during the registration and lock-up period to the public trading price of the common stock, which is a Level 1 input, on the date of sale. The Company determined the value of the lack of marketability during the registration and lock-up period by utilizing put option models, which are considered Level 3 inputs. Such option models included the Company’s historical volatility of 113.2% and the risk-free rate of 5.28% based on U.S. Treasury bond rates, as key inputs. The Company recognized $0.8 million and $0.6 million, respectively, in revenue during the years ended December 31, 2025 and 2024, related to data collection and data submission with the identified performance obligations, and the premium and discount allocated to revenue from the sale of the common stock to JJDC. The remaining revenue is included in deferred revenue on the Company’s consolidated balance sheets as of December 31, 2025, and will be recognized as the performance obligations are satisfied. The Company determined that the J&J Collaboration Agreement is not in the scope of ASC 808, Collaborative Arrangements . Asset Acquisition In May 2022, we obtained worldwide exclusive rights to RLYB331, with Kymab Limited (“Sanofi”) a preclinical antibody. In 2024, we re-engineered RLYB331 to extend its half-life and renamed the program RLYB332. We believe RLYB332 has the potential to address a significant unmet need for patients with severe anemias with ineffective erythropoiesis and iron overload, including beta thalassemia and a subset of lower risk myelodysplastic syndromes (“MDS”). Under the terms of the license agreement, we made an upfront payment to Sanofi of $3.0 million in the second quarter of 2022 for the exclusive license to KY1066. We could also be required to pay up to an aggregate of $43.0 million in development and regulatory milestones and up to an aggregate of $150.0 million in commercial milestones for a product in its first indication, plus tiered low-to-mid double digit percentages of such milestone amounts for up to three additional indications, and mid to high single digit royalties on net sales. The license was accounted for as an asset acquisition as substantially all of the fair value of the asset acquired was concentrated in a single asset and thus the acquisition was deemed not to be a business combination. The acquired license rights represent an IPR&D asset that was determined to have no alternative future use. Accordingly, the Company recorded an IPR&D charge of $3.1 million to research and development expense, including transaction costs associated with this asset acquisition of $0.1 million, in the consolidated statements of operations and comprehensive loss for the year ended December 31, 2022. The Company did not record an IPR&D charge for the years ending December 31, 2025 and 2024 and did not achieve any milestones related to the terms of the license agreement. AbCellera Collaboration In December 2022, the Company entered into a multi-year, multi-target collaboration with AbCellera Biologics Inc. (“AbCellera”) to discover, develop, and commercialize novel antibody-based therapeutics for rare diseases. Under the terms of the agreement, AbCellera and Rallybio will co-develop and share the development costs of up to five rare disease therapeutic targets, which will be chosen together by both companies. At the point one party in the collaboration opts-out of future co-development cost sharing, that party will be entitled to a share of future profit sharing from commercialization of the collaboration target, dependent on the proportion of their co-development contributions compared to the total development costs of a target as defined within the agreement. The agreement also has defined profit sharing floors that correspond to the stage of development at the time a collaboration party opts-out of co-developing a target. The Company concluded that the agreement with AbCellera will be accounted under the scope of ASC 808 as both parties will actively participate in joint operating activities and are exposed to significant risks and rewards that depend on the commercial success of those activities. Under ASC 808, certain transactions between collaborative arrangement participants should follow the accounting for revenue under ASC 606 when the collaborative arrangement participant is a customer. The Company determined that co-development arrangement as defined in our agreement with AbCellera does not meet the definition of a customer as defined by ASC 606. As a result, these activities will be accounted for as research and development costs. Payments due because of the co-development will be recorded as research and development expense in the period such expenses are incurred and for payments owed to us from our collaboration partner for the reimbursement of research and development costs will be recorded as a contra-research and development expense in the period such expenses are incurred. Costs related to the AbCellera collaboration were $0.4 million for the year ended December 31, 2024. There were no costs related to the AbCellera collaboration for the year ended December 31, 2025.