BUSINESS AND LIQUIDITY	3 Months Ended
Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
BUSINESS AND LIQUIDITY	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.

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 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.