Astria Therapeutics Announces Positive Initial Results from the ALPHA-SOLAR Long-Term Open-Label Trial of Navenibart in Hereditary Angioedema Patients at the European Academy of Allergy and Clinical Immunology Annual Congress

-- Q3M Arm Demonstrated 95% Mean Monthly Attack-Rate Reduction --

-- Q6M Arm Demonstrated 86% Mean Monthly Attack-Rate Reduction –

-- Well-Tolerated with a Favorable Safety Profile --

-- All Patients Remain on Navenibart --

-- Long-Term Data are Highly Consistent with Previous Results and Support the Potential Market-Leading Profile of Navenibart, Administered 2 or 4 Times Per Year --

-- Phase 3 ALPHA-ORBIT Trial Underway and Enrolling Patients --

Astria Therapeutics, Inc. (NASDAQ:ATXS), a biopharmaceutical company focused on developing life-changing therapies for allergic and immunologic diseases, today announced positive initial results from the target enrollment group in the ongoing ALPHA-SOLAR long-term open-label trial evaluating navenibart (STAR-0215), a monoclonal antibody inhibitor of plasma kallikrein, in hereditary angioedema (HAE) patients. These results demonstrated robust overall reduction in the monthly attack rate (92% mean and 97% median). These results further support navenibart's favorable safety and tolerability profile, and potential every three- (Q3M) and every six-month (Q6M) dosing regimens.

"We are thrilled to share positive initial results from the ALPHA-SOLAR long-term open-label trial," said Christopher Morabito, M.D., Chief Medical Officer at Astria Therapeutics. "Results are consistent with navenibart's best-in-class profile that we saw in the ALPHA-STAR Phase 1b/2 trial. With now 12 to 18 months on navenibart, these ALPHA-SOLAR results support navenibart's favorable profile and the potential to administer navenibart every 3 and every 6 months. The Phase 3 ALPHA-ORBIT trial is evaluating both every 3- and every 6-month regimens and is actively enrolling patients. Navenibart's profile and results that we have seen to date demonstrate the potential for navenibart to be the market-leading HAE therapy."

"The navenibart results in patients to date support the potential for patients to have long-acting protection from their HAE attacks with very low treatment burden," said Dr. William Yang, M.D., PRCPC, FAAAAI, Chair, Ottawa Allergy Research Corporation and Red Maple Trials Inc. "We are excited for the Phase 3 ALPHA-ORBIT trial and believe that navenibart's profile with infrequent dosing could allow patients to spend less time thinking about their HAE, and more time living their lives."

ALPHA-SOLAR is a long-term open-label trial in adults with HAE Type 1 or 2 designed to assess long-term safety and efficacy of navenibart. All 16 target enrollment participants from the Phase 1b/2 ALPHA-STAR trial elected to enroll in ALPHA-SOLAR. ALPHA-STAR patients from Cohorts 1 and 2 enrolled in Arm A, and ALPHA-STAR patients from Cohort 3 enrolled in Arm B (described in the table below).

Initial results from ALPHA-SOLAR¹:

1. Comparisons to baseline from ALPHA-STAR.

Navenibart demonstrated overall attack-freedom of 50% over six months, which is the longest period of follow-up for all 16 patients to date. All patients remain in the ALPHA-SOLAR trial. Navenibart was well-tolerated with no severe or serious treatment-emergent adverse events (TEAEs) and no discontinuations. One participant experienced two treatment-related, mild injection site reactions that resolved without treatment. There were no injection site reactions of pain. The safety profile of navenibart in patients with HAE was favorable through more than 17 months (median / mean) of cumulative follow-up since the initiation of navenibart in ALPHA-STAR.

The results shared above are available in a poster presented at the European Academy of Allergy and Clinical Immunology (EAACI) Annual Congress on June 13, 2025. The poster is accessible to conference attendees and also in the Scientific Presentations and Publications section of www.astriatx.com.

In February 2025, Astria initiated the pivotal Phase 3 ALPHA-ORBIT trial, which is evaluating navenibart administered Q3M and Q6M and currently enrolling patients. For more information, visit clinicaltrials.gov, NCT06842823 or alphaorbit.longboat.com.

About Navenibart:

Navenibart is a monoclonal antibody inhibitor of plasma kallikrein in development for the treatment of HAE. Our goal with navenibart is to provide rapid and sustained HAE attack prevention with a validated mechanism and trusted modality administered subcutaneously every 3 and 6 months. We aim to empower people living with HAE to live life without limitations from their disease.

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 a monoclonal antibody inhibitor of plasma kallikrein in clinical development for the treatment of hereditary angioedema. Our second program, STAR-0310, is a monoclonal antibody OX40 antagonist in preclinical 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: our expectations regarding the potential significance of the results from the navenibart Phase 1b/2 ALPHA-STAR clinical trial and initial results from the ALPHA-SOLAR trial; the goals and objectives of the ALPHA-ORBIT trial; the potential therapeutic benefits of navenibart as a treatment for HAE; the potential attributes and profile of navenibart as a treatment for HAE, including its potential to be a life-changing, market leading preventative treatment for HAE, and our overall vision and goals for the navenibart program; and our corporate strategy and vision, including our mission is to bring life-changing therapies to patients and families affected by allergic and immunologic diseases. 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 the 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 risks and uncertainties related to: 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 may not be replicated in clinical trials, that the preliminary, initial 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 ALPHA-STAR Phase 1b/2 clinical trial, may not be replicated in later stage clinical trials, such as the planned Phase 3 development program, 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 U.S. Food and Drug Administration 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; our ability to manufacture sufficient quantities of drug substance and drug product for navenibart, STAR-0310, and any other future product candidates on a cost-effective and timely basis, and to develop dosages and formulations 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 therefor; 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, modeling data 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 that any of our clinical trials of STAR-0310 may not commence, continue or be completed on time, or at all; risks that results of preclinical studies of STAR-0310 will not be replicated in clinical trials; 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 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" section of our Annual Report on Form 10-K for the period ended December 31, 2024 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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