Enanta's Zelicapavir Misses Primary, Shows Secondary Benefits

Enanta Pharmaceuticals released topline data from its Phase 2b RSVHR study of zelicapavir in high‑risk outpatient adults and reported the trial missed its primary endpoint (no significant effect on time to resolution of the LRTD subset of four symptoms to mild). The company said zelicapavir produced a robust antiviral effect, a favorable safety profile, and met multiple key secondary endpoints, including a clinically meaningful 2.2‑day improvement in time to complete resolution of all 13 RSV symptoms overall (6.7 days in the HR3 high‑risk subgroup), improvements on the 29‑parameter RiiQ symptom scale, faster PGI‑S recovery (about two days), and lower hospitalization rates. Enanta characterized the totality of the data as supportive of Phase III development and identified potential registrational endpoints; zelicapavir is a once‑daily oral N‑protein inhibitor with FDA Fast Track designation. The company scheduled a conference call and webcast to present topline results on September 29, 2025, and the readout lifted Enanta's shares in after‑hours and premarket trading.