Rallybio Announces Positive Data for RLYB116 Phase 1 Study Demonstrating Complete and Sustained Inhibition of Terminal Complement

Key Terms

c5 inhibitor medical

A C5 inhibitor is a medicine that blocks a specific protein (complement component 5) in the immune system that, when overactive, can cause red blood cell destruction, clotting or inflammation. For investors, C5 inhibitors matter because they target rare but serious diseases where effective treatments can command premium pricing and steady demand; their development and approval carry high reward but also significant clinical and regulatory risk, like putting a precise brake on a malfunctioning engine.

antiphospholipid syndrome medical

A disorder in which the immune system mistakenly targets certain blood-coating proteins, causing the blood to clot more easily and sometimes leading to strokes, deep vein clots, pregnancy loss, or other organ damage. Investors should care because the condition affects demand for diagnostics, therapies and monitoring, can influence clinical trial design and regulatory risk for related drugs, and may create liability or market opportunity similar to a new safety standard reshaping an industry.

subcutaneously medical

Given or delivered beneath the skin into the fatty layer just under the surface, usually by injection or a small device. For investors, whether a medicine is given subcutaneously affects how easy it is for patients to use, how often doses are needed, and the cost and complexity of manufacturing and regulation—think of it like placing a slow-release patch under a carpet instead of pouring medicine on top of it, which changes convenience and ongoing demand.

autoinjector technical

A prefilled, spring‑loaded medical device that automatically delivers a measured dose of medication beneath the skin when pressed against the body, like a self‑operating syringe packaged for quick use. Investors care because autoinjectors can increase patient safety, adherence and convenience — factors that drive demand, shape reimbursement and regulatory review, and affect a product’s market size, manufacturing complexity and competitive moat.

– Data Support the Study of RLYB116 as a Potential Best-In-Class Therapeutic for Multiple Complement Mediated Diseases –

– Initiation of RLYB116 Phase 2 Clinical Trial in Immune Platelet Transfusion Refractoriness Currently Planned for 2H 2026 with Potential for Topline Data in 2027 –

NEW HAVEN, Conn.--(BUSINESS WIRE)-- Rallybio Corporation (Nasdaq: RLYB), a clinical-stage biotechnology company translating scientific advances into transformative therapies for patients with devastating rare diseases, today announced positive results from its Phase 1 confirmatory pharmacokinetic/pharmacodynamic (PK/PD) clinical trial evaluating RLYB116, the Company’s innovative, once-weekly, small volume, subcutaneously injected C5 inhibitor, in development for patients with complement-mediated diseases with its initial focus on immune platelet transfusion refractoriness (PTR) and refractory antiphospholipid syndrome (APS).

“The results from our Phase 1 study of RLYB116 are both validating and highly encouraging, reinforcing our belief that this program has the potential to be a best-in-class therapeutic. At the 300 mg dose, we achieved complete and sustained inhibition of terminal complement with a safety profile consistent with other subcutaneous biologics,” stated Stephen Uden, M.D., Co-Founder and Chief Executive Officer of Rallybio. “These data underscore the potential of RLYB116 to deliver rapid onset, durable activity, and patient-friendly administration through a small volume, off-the-shelf autoinjector—features that could transform care for individuals living with complement-mediated diseases such as immune platelet transfusion refractoriness and antiphospholipid syndrome.”

The single-blind multiple ascending dose Phase 1 confirmatory PK/PD study of RLYB116 (NCT06797375) was designed to demonstrate complete and sustained complement inhibition with favorable tolerability in healthy volunteers. The study evaluated a 4-week treatment duration that included two cohorts of eight participants each, randomized 3-to-1 to receive either RLYB116 or placebo once weekly. Cohort 1 evaluated dosing of 150 mg and Cohort 2 evaluated dosing of 300 mg. The study included a 10-week follow-up period after the conclusion of treatment.

“With these results in hand, we have the potential to move into a Phase 2 proof of concept study in immune PTR, in 2H 2026. We remain steadfast in our belief that RLYB116 has significant value as a potential best-in-class therapy for patients with high unmet need,” concluded Dr. Uden.

The data demonstrated the following:

• A 300 mg once-a-week dose of subcutaneously administered RLYB116 achieved complete and sustained inhibition of terminal complement.
• Complete and sustained inhibition of ex-vivo hemolytic activity demonstrates clinically effective blockade of terminal complement.
• RLYB116 administered as a 150 mg and 300 mg once-a-week dose was well tolerated with no gastrointestinal side effects reported among participants. The most common adverse events in both cohorts were mild-to-moderate injection site reactions, consistent with other subcutaneously administered biologics. None were severe or caused discontinuation of study drug. These results further validate the manufacturing process enhancements designed to improve the tolerability profile of RLYB116.

“Based on our prior clinical experience, the Phase 1 results are compelling and provide strong corroboration for our scientific and clinical rationale. The data demonstrate the potential for rapid onset and sustained activity, offering clinical benefit and flexibility for a convenient dosing regimen that addresses a significant unmet need for patients with immune PTR, APS and other complement mediated diseases,” said Steven Ryder, M.D., Chief Medical Officer of Rallybio.

About Rallybio
Rallybio (NASDAQ: RLYB) is a clinical-stage biotechnology company with a mission to develop and commercialize life-transforming therapies for patients with severe and rare diseases. Rallybio has built a pipeline of promising product candidates aimed at addressing diseases with unmet medical need in areas of complement dysregulation and hematology. The Company’s lead program, RLYB116, is a differentiated C5 inhibitor with the potential to treat diseases of complement dysregulation, with an initial focus on immune platelet transfusion refractoriness and refractory antiphospholipid syndrome. Rallybio’s pipeline also includes RLYB332, a preclinical long-acting matriptase-2 antibody for the treatment of diseases of iron overload. Rallybio is headquartered in New Haven, Connecticut. For more information, please visit www.rallybio.com and follow us on LinkedIn.

Forward-Looking Statements
This press release contains forward-looking statements that are based on our management’s beliefs and assumptions and currently available information. All statements, other than statements of historical facts contained in this press release are forward-looking statements. In some cases, forward-looking statements can be identified by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions, although not all forward-looking statements contain these words. Forward-looking statements in this press release include, but are not limited to, statements concerning the timing to initiate and have topline data from a Phase 2 clinical trial of RLYB116, the potential for RLYB116 to be a best-in-class therapeutic, and the potential of RLYB116 to transform care for individuals living with complement-mediated diseases. The forward-looking statements in this press release are only predictions and are based largely on management’s current expectations and projections about future events and financial trends that management believes may affect Rallybio’s business, financial condition and results of operations. These forward-looking statements speak only as of the date of this press release and are subject to a number of known and unknown risks, uncertainties and assumptions, including, but not limited to, our ability to successfully conduct the RLYB116 Phase 2 clinical trial and complete such study and obtain results on our expected timelines, or at all, the potential result of such clinical trials and those risks and uncertainties described in Rallybio’s filings with the U.S. Securities and Exchange Commission (SEC), including the Quarterly Report on Form 10-Q for the period ended September 30, 2025, and subsequent filings with the SEC. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual future results, levels of activity, performance and events and circumstances could differ materially from those projected in the forward-looking statements. Except as required by applicable law, we are not obligated to publicly update or revise any forward-looking statements contained in this press release, whether as a result of any new information, future events, changed circumstances or otherwise.

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Source: Rallybio Corporation