Exhibit 99.1 Altimmune Announces First Quarter 2024 Financial Results and Provides a Business Update Enrollment ongoing in IMPACT Phase 2b trial of pemvidutide in Metabolic Dysfunction-Associated Steatohepatitis (MASH), with top line results expected in Q1 2025 Cash, cash equivalents and short-term investments of $182.1 million at March 31, 2024 Webcast to be held today, May 9, 2024, at 8:30 am ET GAITHERSBURG, MD – May 9, 2024 – Altimmune, Inc. (Nasdaq: ALT), a clinicalstage biopharmaceutical company, toda ...