Material Event (Form 8-K)

On September 29, 2026, Phathom Pharmaceuticals, Inc. ("Phathom" or the "Company") announced the initiation of patient screening in pHalcon-NERD-302, a registrational Phase 3 study evaluating an as-needed (PRN or on-demand) investigational dosing regimen of VOQUEZNA (vonoprazan) tablets in adults with Non-Erosive Gastroesophageal Reflux Disease, or Non-Erosive GERD (NERD). Topline results are expected in the first quarter of 2028. If successful, the study is intended to support a potential regulatory submission seeking a label expansion for VOQUEZNA tablets for this treatment regimen.

Building on previously reported positive Phase 2 results, pHalcon-NERD-302 is a multicenter, randomized, double-blind, placebo-controlled Phase 3 study investigating VOQUEZNA 10 mg as an as-needed treatment in adults with Non-Erosive GERD. The Phase 3 pHalcon-NERD-302 study is expected to enroll approximately 500 adults with Non-Erosive GERD who report heartburn at least four days per week. The study is planned to be conducted at approximately 80 sites in the U.S. Following a four-week, open-label run-in period with VOQUEZNA 10 mg once daily, patients without heartburn during the final seven days of the run-in period will be randomized 1:1 to receive VOQUEZNA 10 mg or placebo, as-needed, for 24 weeks of treatment. The primary endpoint, assessed at Week 12, is the percentage of heartburn episodes in which patients experience complete relief within two hours and sustained relief for 24 hours post-dosing.