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Enanta Pharmaceuticals Announces Advancement of its Zelicapavir Clinical Development Program for the Treatment of Respiratory Syncytial Virus (RSV)

ENTA
  • Enanta Pharmaceuticals will initiate a registrational Phase 2b/3 trial for zelicapavir in high-risk adults with RSV in the fourth quarter of 2026.
  • Topline data from the Phase 2b portion of the adult trial is expected in 2027.
  • A separate Phase 2b trial for zelicapavir in pediatric patients is scheduled to start in the third quarter of 2026.
  • Pediatric trial topline data is also projected for 2027, conducted in collaboration with the Penta Foundation & the AMS-PHPT Research Unit at Chiang Mai University.
  • The adult Phase 2b/3 study will evaluate 800mg oral doses of zelicapavir in patients aged 75+, or those with COPD or CHF, with a primary endpoint of time to complete symptom resolution.
  • The adult trial includes a minimum of 200 patients in the Phase 2b portion to confirm efficacy, followed by approximately 660 patients in the Phase 3 portion.
  • The pediatric Phase 2b study will involve approximately 150 participants aged 28 days to 36 months, receiving weight-based dosing (5mg/kg or 7.5mg/kg) for 7 days.
  • Zelicapavir has received Fast Track designation from the FDA & targets the RSV N-protein to inhibit viral replication.
  • Previous Phase 2 data showed a 6.7-day reduction in symptom resolution time for high-risk adults & a 0% hospitalization rate for treated patients compared to 5% for placebo.
  • Enanta estimates a global market opportunity for an oral RSV antiviral exceeding $2 billion, with a total addressable population of over 3 million patients in the U.S.