BUSINESS

12 Months Ended

Dec. 31, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

BUSINESS

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

subscription agreements 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. If the Merger is completed, the business of Candid will continue as the business of the combined company.