SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES BASIS OF PRESENTATION AND PRINCIPLES OF CONSOLIDATION (Policies)	6 Months Ended
Jun. 30, 2026
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 ("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 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 and six months ended June 30, 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	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.
Income Taxes	Income Taxes The Company’s effective tax rates for the six months ended June 30, 2026 and 2025 were 9.6% and 0%, respectively. The primary drivers of the variance from the statutory rate were state taxes, Section162 disallowed compensation, nondeductible stock-based compensation, and valuation allowance. The Company will continue to assess its estimated annual effective tax rate each reporting period. In assessing the realization of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the period in which those temporary differences become deductible. Management considers the Company’s history of cumulative net losses, the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment. The Company has determined that, based on objective positive and negative evidence currently available, it is more likely than not that the Company will not realize the benefits of all deferred tax assets. Accordingly, the Company has provided a full valuation allowance for the deferred tax assets. The Company is expecting to have net taxable income for the current year, resulting in current income tax expense for the period. This is primarily due to income resulting from the termination of the Candid Merger Agreement and the termination fee recorded during the quarter. As of June 30, 2026, the Company has federal and state post-apportioned net operating loss (“NOL”) carryforwards of approximately $179.5 million and $167.3 million, respectively. All federal NOL carryforwards have an indefinite carryforward period. All state NOL carryforwards have a limited carryforward period and will begin to expire in 2038. As of June 30, 2026, the Company has federal general business tax credits of approximately $24.5 million which have a limited carryforward period and will begin to expire in 2039. Utilization of the NOL carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 (the "Code"), and corresponding provisions of state law, due to ownership changes that 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. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50% over a three-year period. The Company completed a Section 382 study through June 30, 2021 and concluded that it underwent an ownership change as defined by the Code on March 27, 2020. The Company completed a high-level analysis for the period July 1, 2021 through June 30, 2026 and does not believe any additional ownership changes occurred during that period. Any future ownership changes that may occur after June 30, 2026, may limit the Company’s ability to utilize remaining tax attributes. Due to the existence of the valuation allowance, limitations created by the 2020 ownership change and any potential future ownership changes will not impact the Company’s effective tax rate.
Recently Issued Accounting Pronouncements	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.

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

6 Months Ended

Jun. 30, 2026

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 ("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 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 and six months ended June 30, 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.

Income Taxes

The Company’s effective tax rates for the six months ended June 30, 2026 and 2025 were 9.6% and 0%, respectively. The primary drivers of the variance from the statutory rate were state taxes, Section162 disallowed compensation, nondeductible stock-based compensation, and valuation allowance. The Company will continue to assess its estimated annual effective tax rate each reporting period.

In assessing the realization of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax assets will be realized. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the period in which those temporary differences become deductible. Management considers the Company’s history of cumulative net losses, the scheduled reversal of deferred tax liabilities, projected future taxable income and tax planning strategies in making this assessment. The Company has determined that, based on objective positive and negative evidence currently

available, it is more likely than not that the Company will not realize the benefits of all deferred tax assets. Accordingly, the Company has provided a full valuation allowance for the deferred tax assets. The Company is expecting to have net taxable income for the current year, resulting in current income tax expense for the period. This is primarily due to income resulting from the termination of the Candid Merger Agreement and the termination fee recorded during the quarter.

As of June 30, 2026, the Company has federal and state post-apportioned net operating loss (“NOL”) carryforwards of approximately $179.5 million and $167.3 million, respectively. All federal NOL carryforwards have an indefinite carryforward period. All state NOL carryforwards have a limited carryforward period and will begin to expire in 2038. As of June 30, 2026, the Company has federal general business tax credits of approximately $24.5 million which have a limited carryforward period and will begin to expire in 2039.

Utilization of the NOL carryforwards may be subject to a substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 (the "Code"), and corresponding provisions of state law, due to ownership changes that 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. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain stockholders or public groups in the stock of a corporation by more than 50% over a three-year period.

The Company completed a Section 382 study through June 30, 2021 and concluded that it underwent an ownership change as defined by the Code on March 27, 2020. The Company completed a high-level analysis for the period July 1, 2021 through June 30, 2026 and does not believe any additional ownership changes occurred during that period. Any future ownership changes that may occur after June 30, 2026, may limit the Company’s ability to utilize remaining tax attributes. Due to the existence of the valuation allowance, limitations created by the 2020 ownership change and any potential future ownership changes will not impact the Company’s effective tax rate.

Recently Issued Accounting Pronouncements

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.