-- Final ALPHA-STAR Phase 1b/2 Results from the Full-Enrollment Population (n=29) Remain Highly Consistent with Prior Results from the Target-Enrollment Population (n=16), Demonstrating Strong Efficacy, Favorable Safety, and Potential for Infrequent Dosing --

-- Phase 3 ALPHA-ORBIT Trial for Navenibart is Progressing as Planned with Topline Results Anticipated in Early 2027; First Patient Now Enrolled in the ORBIT-EXPANSE Long-Term Extension Trial --

Astria Therapeutics, Inc. (NASDAQ: ATXS), a biopharmaceutical company focused on developing life-changing therapies for allergic and immunologic diseases, today announced positive results from the full enrollment group of 29 patients in the ALPHA-STAR Phase 1b/2 clinical trial evaluating navenibart (STAR-0215), a monoclonal antibody inhibitor of plasma kallikrein, in hereditary angioedema (HAE) patients. Conducted across 20 sites in six countries, the trial demonstrated robust attack rate reduction, along with a favorable safety and tolerability profile, supporting both every three-month (Q3M) and every six-month (Q6M) dosing regimens. These results reinforce the potential of navenibart’s profile to provide effective, long-acting prevention from HAE attacks and highlight Astria’s strong global clinical execution as the Phase 3 program progresses, with topline results expected in early 2027.

“The updated results from the full 29 patients in the ALPHA-STAR Phase 1b/2 trial are highly encouraging and reinforce our confidence in navenibart’s profile as a potentially life-changing preventative treatment for HAE,” said Christopher Morabito, M.D., Chief Medical Officer at Astria Therapeutics. “With nearly double the target enrollment, the data are highly consistent with previously reported results and demonstrate rapid onset, robust and durable efficacy, and a favorable safety and tolerability profile. Importantly, we also observed sustained, clinically meaningful improvements in patient-reported quality of life. The results strongly support both Q3M and Q6M dosing regimens, and we look forward to navenibart's progress in the ALPHA-ORBIT Phase 3 trial, which is enrolling globally.”

ALPHA-STAR is a dose-ranging proof-of-concept trial in adults with HAE Type 1 or 2 designed to assess safety, tolerability, efficacy, pharmacokinetics (PK), pharmacodynamics (PD), and quality of life in patients receiving single and multiple doses of navenibart in three cohorts delivered subcutaneously to prevent attacks in HAE. All cohorts began with an eight-week run-in period to measure baseline HAE attacks followed by safety, efficacy, PK, and PD evaluation through 6-months after the last dose received (Day 168, 252, and 196 for Cohorts 1, 2, and 3, respectively). Due to faster-than-expected enrollment and patient interest beyond the original target enrollment of 16, the trial was expanded in Cohorts 2 and 3 and ultimately enrolled a total of 29 patients. These additional patients also contribute to the navenibart safety database for future regulatory filings. The mean/median percent reduction in attack rate from baseline through six months of treatment in the ALPHA-STAR trial are summarized in the following table:

Through six months of treatment, expanded Cohorts 2 and 3 had a 62% and 67% attack-free rate, respectively, consistent with previously reported results. Clinically meaningful improvements in patient-reported quality of life (AE-QoL total score) were demonstrated at 6 months (Cohort 1: -25.37; Cohort 2: -31.79; Cohort 3: -21.03).

Navenibart was generally well-tolerated with no serious treatment-emergent adverse events (TEAEs), no discontinuations, and no injection site reactions of pain. There were four non-severe and quickly resolved treatment-related TEAEs: one case of dizziness, a transient injection site reaction (rash), an injection site erythema, and an injection site pruritus.

All 29 (100%) patients in the ALPHA-STAR trial elected to enroll in the ALPHA-SOLAR long-term open-label trial and continue receiving navenibart.

About Astria Therapeutics:

Astria Therapeutics is a biopharmaceutical company, and our mission is to bring life-changing therapies to patients and families affected by allergic and immunologic diseases. Our lead program, navenibart (STAR-0215), is an investigational monoclonal antibody inhibitor of plasma kallikrein in clinical development for the treatment of hereditary angioedema. Our second program, STAR-0310, is an investigational monoclonal antibody OX40 antagonist in clinical development for the treatment of atopic dermatitis. Learn more about our company on our website, www.astriatx.com, or follow us on Instagram @AstriaTx and on Facebook and LinkedIn.

Forward Looking Statements:

This press release contains forward-looking statements within the meaning of applicable securities laws and regulations including, but not limited to, statements regarding: the potential significance of the ALPHA-STAR data, including that it demonstrates that navenibart has rapid onset, robust and durable efficacy, a favorable safety and tolerability profile, and could improve the quality of life of HAE patients; the expected timing of receipt of topline results from the navenibart ALPHA-ORBIT Phase 3 trial; our goal of developing two dosing options for navenibart; the potential for navenibart in the HAE market and the potential therapeutic and other benefits of navenibart as a treatment for HAE, and our vision and goals for the program; ; and the goal of bringing life changing therapies to patients and families affected by allergic and immunological diseases and to become a leading allergy and immunology company. The use of words such as, but not limited to, “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “goals,” “intend,” “may,” “might,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “will,” “would,” or "vision," and similar words expressions are intended to identify forward-looking statements. Forward-looking statements are neither historical facts nor assurances of future performance. Instead, they are based on Astria’s current beliefs, expectations and assumptions regarding the future of its business, future plans and strategies, future financial performance, results of pre-clinical and clinical results of Astria’s product candidates and other future conditions. Actual results may differ materially from those indicated by such forward-looking statements as a result of various important factors, including the following risks and uncertainties: changes in applicable laws or regulations; the possibility that we may be adversely affected by other economic, business, and/or competitive factors; risks inherent in pharmaceutical research and development, such as: adverse results in our drug discovery, preclinical and clinical development activities, the risk that the results of preclinical studies, including of navenibart and STAR-0310, may not be replicated in clinical trials, that the preliminary or interim results from clinical trials may not be indicative of the final results, that the results of early stage clinical trials, such as the results from the navenibart Phase 1a clinical trial and the results from the ALPHA-STAR trial, may not be replicated in later stage clinical trials, including the ALPHA-ORBIT Phase 3 trial or the ORBIT-EXPANSE long-term extension trial; the risk that we may not be able to enroll sufficient patients in our clinical trials on a timely basis, and the risk that any of our clinical trials may not commence, continue or be completed on time, or at all; decisions made by, and feedback received from, the FDA and other regulatory authorities on our regulatory and clinical trial submissions and other feedback from potential clinical trial sites, including investigational review boards at such sites, and other review bodies with respect to navenibart, STAR-0310, and any other future development candidates, and devices for such product candidates; our ability to manufacture sufficient quantities of drug substance and drug product for navenibart, STAR-0310, and any other future product candidates, and devices for such product candidates, on a cost-effective and timely basis, and to develop dosages and formulation for navenibart, STAR-0310, and any other future product candidates that are patient-friendly and competitive; our ability to develop biomarker and other assays, along with the testing protocols therefore; our ability to obtain, maintain and enforce intellectual property rights for navenibart, STAR-0310, and any other future product candidates; our potential dependence on collaboration partners; competition with respect to navenibart, STAR-0310, or any of our other future product candidates; the risk that survey results and market research may not be accurate predictors of the commercial landscape for HAE, the ability of navenibart to compete in HAE and the anticipated position and attributes of navenibart in HAE based on clinical data to date, its preclinical profile, pharmacokinetic modeling, market research and other data; risks with respect to the ability of STAR-0310 to compete in AD and the anticipated position and attributes of STAR-0310 in AD based on its preclinical profile; our ability to manage our cash usage and the possibility of unexpected cash expenditures; our ability to obtain necessary financing to conduct our planned activities, including the costs associated with commercialization of navenibart if regulatory approval is obtained, and to manage unplanned cash requirements; the risks and uncertainties related to our ability to recognize the benefits of any additional acquisitions, licenses or similar transactions; and general economic and market conditions; as well as the risks and uncertainties discussed in the “Risk Factors” sections of our Annual Report on Form 10-K for the period ended December 31, 2024 and our Quarterly Report on Form 10-Q for the quarter ended June 30, 2025, and in other filings that we may make with the Securities and Exchange Commission.

New risks and uncertainties may emerge from time to time, and it is not possible to predict all risks and uncertainties. Astria may not actually achieve the forecasts or expectations disclosed in our forward-looking statements, and investors and potential investors should not place undue reliance on Astria’s forward-looking statements. Neither Astria, nor its affiliates, advisors or representatives, undertake any obligation to publicly update or revise any forward-looking statement, whether as result of new information, future events or otherwise, except as required by law. These forward-looking statements should not be relied upon as representing Astria’s views as of any date subsequent to the date hereof.

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