Rallybio Reports Third Quarter 2025 Financial Results and Provides Business Updates - RLYB116 Confirmatory PK PD Study Data Expected in 4Q 2025 - - Generated $20 Million from Sale of Interest in REV102 - - Cash Runway Ex

Rallybio Reports Third Quarter 2025 Financial Results and Provides Business Updates

- RLYB116 Confirmatory PK PD Study Data Expected in 4Q 2025 -

- Generated $20 Million from Sale of Interest in REV102 -

- Cash Runway Extended through 2027 -

NEW HAVEN, Conn., November 6, 2025 -- Rallybio Corporation (Nasdaq RLYB), a clinical-stage biotechnology company translating scientific advances into transformative therapies for patients with devastating rare diseases, today reported financial results for the third quarter ended September 30, 2025, and provided an update on recent company developments.

"In the third quarter, we continued to execute with discipline and focus, advancing our lead program, RLYB116, and achieving a key clinical milestone with the completion of dosing in Cohort 1 in our confirmatory PK PD Phase 1 study," said Stephen Uden, M.D., Chief Executive Officer of Rallybio. "In parallel, we strengthened our balance sheet with non-dilutive capital received from the sale of our interest in REV102. With the second cohort of the RLYB116 study progressing, we remain on track to report data in the fourth quarter of 2025 and are increasingly confident in RLYB116's potential to be an effective therapeutic. Our internal and external market assessments further validate the importance of advancing this program, as we plan for the next stage in development and in RLYB116's potential to address serious unmet needs in complement-mediated diseases."

Recent Business Highlights and Upcoming Milestones

In the third quarter of 2025, Rallybio generated a total of $20 million pursuant to its agreement with Recursion Pharmaceuticals for the sale of its interest in REV102, an investigational ENPP1 inhibitor in development for the treatment of hypophosphatasia (HPP). The total included $7.5 million from an upfront payment and $12.5 million related to the initiation of additional preclinical studies.

In September 2025, Rallybio completed dosing of Cohort 1 in the RLYB116 Phase 1 confirmatory pharmacokinetic pharmacodynamic (PK PD) clinical trial, which is planned for development in two hematologic conditions with significant unmet need immune platelet transfusion refractoriness (PTR) and refractory antiphospholipid syndrome (APS).The Phase 1 study is designed to demonstrate complete and sustained complement inhibition as well as favorable tolerability. Data from Cohort 1 support the advancement of RLYB116 as a differentiated therapeutic and enables progression to Cohort 2. Rallybio is on track to report data from the study in the fourth quarter of 2025.

Rallybio continues to evaluate plans for future development of RLYB332, a long-acting, monoclonal anti-matriptase-2 antibody with the potential to be a best-in-class treatment for diseases of iron overload. Preclinical data have demonstrated superior impact on PD parameters, including serum iron, unsaturated iron binding capacity, and transferrin saturation, relative to comparator molecules.

Third Quarter 2025 Financial Results

Revenue Revenue was $0.2 million for the third quarter of 2025, compared to $0.3 million for the same period in 2024. The decrease in revenue for the third quarter of 2025 was related to the collaboration agreement with Johnson Johnson in the third quarter of 2024 and the recognition of revenue related to the collaboration's performance obligations.

Research Development (R D) Expenses R D expenses were $4.1 million for the third quarter of 2025, compared to $8.2 million for the same period in 2024. The decrease in R D expenses were primarily due to a decrease in development costs related to RLYB212 and other program candidates, in addition to a decrease in payroll and personnel-related expenses, largely related to the Company's workforce reduction announced in May 2025 offset by an increase in development costs related to RLYB116.

General Administrative (G A) Expenses G A expenses were $3.0 million for the third quarter of 2025, compared to $4.1 million for the same period in 2024. The decrease in G A expenses were primarily due to a decrease in payroll and personnel-related expenses, largely related to lower headcount as compared to the same period in 2024.

Net Loss and Net Loss Per Common Share Rallybio reported a net income of $16.0 million, or $0.36 per common share, for the third quarter of 2025 compared to a net loss of $11.5 million, or $0.26 per common share, for the same period in 2024.

Cash Position As of September 30, 2025, cash, cash equivalents, and marketable securities were $59.3 million. Rallybio expects that its cash, cash equivalents and marketable securities will be sufficient to support operations through 2027.

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 of dosing of Cohort 2 in the RLYB116 confirmatory PK PD study and the periods in which data from the trial are expected to be available, whether the PK PD confirmatory study will demonstrate improved tolerability and complete and sustained inhibition of terminal complement, whether RLYB116 will be effective in treating a broad range of complement-mediated diseases, the potential commercial opportunity for RLYB116, the potential for future development of RLYB332, the potential for RLYB332 to be a best-in-class treatment for diseases of iron overload, and the Company's cash runway. 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 initiate and conduct our planned clinical trials, including the RLYB116 PK PD confirmatory study, and

complete such clinical trials and obtain results on our expected timelines, or at all, whether our cash resources will be sufficient to fund our operating expenses and capital expenditure requirements and whether we will be successful raising additional capital, our ability to enter into strategic partnerships or other arrangements, competition from other biotechnology and pharmaceutical companies, and those risks and uncertainties described in Rallybio's filings with the U.S. Securities and Exchange Commission (SEC), including Rallybio's Quarterly Report on Form 10-Q for the period ended June 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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