Exhibit 99.1 Phathom Pharmaceuticals Reports First Quarter 2026 Financial Results and Provides Business Update FLORHAM PARK, N.J., April 30, 2026 — Phathom Pharmaceuticals, Inc. (Nasdaq: PHAT), a biopharmaceutical company focused on commercializing and developing novel treatments for gastrointestinal (GI) diseases, today reported financial results for the first quarter ended March 31, 2026, and provided a business update. "In the first quarter, we more than doubled revenue compared to the prior year Q1. We ...