Altimmune Appoints Industry Veteran Christophe Arbet-Engels, M.D., PhD as Chief Medical Officer to Drive Next Phase of Clinical Development of Pemvidutide

Seasoned clinical leader to oversee Phase 3 development of pemvidutide in MASH

Dr. Arbet-Engels has led late-stage development, regulatory approvals and commercial launches for multiple successful franchises

GAITHERSBURG, Md., Sept. 29, 2025 (GLOBE NEWSWIRE) -- Altimmune, Inc. (NASDAQ: ALT), a late clinical-stage biopharmaceutical company developing novel peptide-based therapeutics for liver and cardiometabolic diseases, today announced the appointment of Christophe Arbet-Engels, MD, PhD as Chief Medical Officer, effective October 1, 2025. Dr. Arbet-Engels joins the Company with more than 30 years of experience spanning industry, academia and private practice, and will lead the ongoing clinical development of pemvidutide including the planned Phase 3 trial in metabolic dysfunction-associated steatohepatitis (MASH). He succeeds Scott Harris, M.D., who earlier this year informed the Company of his plans to retire from the position. Dr. Harris will remain with the Company as a Senior Strategic Advisor until February 2026.

"We are thrilled to welcome Christophe to the team at this crucial juncture in Altimmune's evolution," said Vipin K. Garg, Ph.D., President and CEO of Altimmune. "He brings a wealth of experience across mid- and late-stage clinical development, regulatory approvals and commercial launches that will be invaluable as we continue to advance pemvidutide and work toward our mission of establishing a new standard of care in the treatment of hepato-metabolic disorders. On behalf of the executive team and Board of Directors, I would also like to thank Scott for his instrumental contributions over the last six years. His oversight of the pemvidutide program through multiple INDs and clinical trials has positioned us well as we prepare to enter Phase 3 development in MASH."

Dr. Arbet-Engels added, "I am proud to join the talented leadership team at Altimmune and excited to lead the development of a therapy as promising as pemvidutide. The data generated to date reinforces the highly differentiated profile of pemvidutide as well as its category-leading potential in MASH. With upcoming 48 week data from the IMPACT trial in MASH, as well as the ongoing Phase 2 trials in Alcohol Use Disorder and Alcohol-associated Liver Disease, pemvidutide presents an exciting opportunity to disrupt the treatment paradigm in three highly prevalent indications and potentially address multiple significant unmet medical needs. I look forward to working closely with Vipin and the rest of the team as we advance to the End-of-Phase 2 meeting with the FDA and continue working toward the initiation of the Phase 3 trial in MASH."

Dr. Arbet-Engels joins Altimmune from X4 Pharmaceuticals (NASDAQ: XFOR), where he served as Chief Medical Officer since 2023. While at X4, he contributed extensively to the successful regulatory process for Xolremdi (mavorixafor), which was approved in 2024 for WHIM Syndrome, and led late-stage clinical programs for mavorixafor in Chronic Neutropenia. Previously, he was Chief Medical Officer at Neurogastrx, Millendo Therapeutics, and Poxel Pharmaceuticals, where he led the clinical development and approval in Japan of Twymeeg for diabetes. Earlier in his career, he held several senior-level medical and clinical positions including at Biogen, Boehringer Ingelheim Pharmaceuticals, Hoffmann-La Roche, Merck Research Laboratories, Aventis Pharmaceuticals, and Ligand Pharmaceuticals, where he led clinical development and registration, launch and lifecycle management efforts for a variety of products including LANTUS® and JARDIANCE®. Prior to his career in industry, Dr. Arbet-Engels served in educational roles at The Salk Institute for Biological Studies, University of Paris VI, and the Assistance Publique, Hospitals of Paris, and he currently serves as a Member of the Board of Tutors in Biochemical Sciences at Harvard University. Dr. Arbet-Engels received his MD and PhD in internal medicine and endocrinology/metabolism from the University of Paris, France, and completed his MBA at Rutgers University. He completed a postdoctoral fellowship in the Department of Medicine, Division of Endocrinology and Metabolism at the University of California, San Diego, and residencies in Endocrinology and Internal Medicine at Military Hospital Bégin, Paris and Assistance Publique, Hospitals of Paris, respectively.

Inducement Grant

In connection with being named as Chief Medical Officer, Dr. Arbet-Engels will receive, in the aggregate, options to purchase 450,000 shares of Altimmune's common stock, and 150,000 restricted stock units ("RSUs"). The options will have an exercise price equal to the closing price of Altimmune's common stock on October 1, 2025 (the "Grant Date"). Based on the closing price of Altimmune's common stock on October 1, 2025, Altimmune would issue approximately 347,436 options as inducement awards under its 2018 Inducement Grant Plan, and the balance as incentive stock options under its 2017 Omnibus Incentive Plan. The final allocation of options between the 2018 Inducement Grant Plan and 2017 Omnibus Plan are subject to adjustment based on the closing price of Altimmune's common stock on the Grant Date. One-fourth of the shares underlying the options will vest on the one-year anniversary of the Grant Date and thereafter 1/36th of the shares underlying the options will vest monthly, such that the shares underlying the options will be fully vested on the fourth anniversary of the Grant Date, in each case, subject to Dr. Arbet-Engels continued employment with Altimmune on such vesting dates.

One-fourth of the RSUs will vest on the one-year anniversary of the Grant Date and thereafter the RSUs will vest in three substantially equal annual installments, such that the RSUs will be fully vested on the fourth anniversary of the Grant Date, in each case, subject to Dr. Arbet-Engel's continued employment with Altimmune on such vesting dates. The equity awards were approved in accordance with Nasdaq Listing Rule 5635(c)(4).

About Altimmune

Altimmune is a late clinical-stage biopharmaceutical company focused on developing novel peptide-based therapeutics for liver and cardiometabolic diseases. The Company's lead product candidate is pemvidutide, a GLP-1/glucagon dual receptor agonist for the treatment of MASH, Alcohol Use Disorder (AUD), Alcohol-associated Liver Disease (ALD) and obesity. For more information, please visit www.altimmune.com.

Forward-Looking Statements

Any statements made in this press release related to the development or commercialization of pemvidutide, an investigational product candidate, and other business, regulatory and financial matters including without limitation, the timing of key milestones for the Company's clinical assets, future plans or expectations for pemvidutide for the treatment of MASH, AUD, ALD and obesity, and the prospects for receiving regulatory approval or commercializing or selling any product or drug candidates, are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. In addition, when or if used in this press release, the words "may," "could," "should," "anticipate," "believe," "estimate," "expect," "intend," "plan," "predict" and similar expressions and their variants, as they relate to Altimmune, Inc. may identify forward-looking statements. The Company cautions that these forward-looking statements are subject to numerous assumptions, risks, and uncertainties, which change over time. Important factors that may cause actual results to differ materially from the results discussed in the forward-looking statements, or historical experience include risks and uncertainties, including risks relating to: delays in regulatory review, manufacturing and supply chain interruptions, access to clinical sites, enrollment, adverse effects on healthcare systems and disruption of the global economy; the reliability of the results of studies relating to human safety and possible adverse effects resulting from the administration of the Company's product candidates; the Company's ability to manufacture clinical trial materials on the timelines anticipated; and the success of future product advancements, including the success of future clinical trials. Further information on the factors and risks that could affect the Company's business, financial conditions and results of operations are contained in the Company's filings with the U.S. Securities and Exchange Commission, including under the heading "Risk Factors" in the Company's most recent annual report on Form 10-K, quarterly report on Form 10-Q and the Company's other filings with the SEC, which are available at www.sec.gov.

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