Enanta Presses Ahead with RSV Drug Zelicapavir Despite Missing Primary Endpoint in Phase IIb Trial
Enanta Pharmaceuticals' RSV drug candidate, zelicapavir, failed to meet its primary endpoint in the Phase IIb trial, showing no significant effect on resolution time of lower respiratory tract disease (LRTD) symptoms, with only a 0.5-day improvement over placebo12.
Despite the primary endpoint miss, zelicapavir achieved clinically meaningful improvements in key secondary endpoints, including a 2.2-day faster resolution of all 13 RSV symptoms and up to 6.7 days faster in high-risk patients (elderly, COPD, or CHF)12.
The drug also demonstrated reduced hospitalization rates (1.7% on zelicapavir vs. 5% for placebo), robust antiviral effects, and was well-tolerated with a favorable safety profile12.
Most participants in the trial were elderly or had chronic conditions like congestive heart failure or COPD, representing a high-risk RSV population12.
Enanta’s stock price more than doubled following the trial results, signaling strong investor confidence in the secondary findings and the drug’s potential1.
Enanta's Chief Medical Officer and analyst commentary highlighted the unprecedented benefit seen in certain subgroups and the identification of multiple potential registrational endpoints for the planned Phase III trial12.
Zelicapavir has received Fast Track designation from the US FDA1.
A Phase III trial for zelicapavir is moving forward, justified by the totality of the Phase IIb data, especially in high-risk adults1245.
Market forecasts expect zelicapavir sales to reach $209 million by 2030, within a rapidly growing RSV prophylaxis market1.
Sources:
1. https://www.clinicaltrialsarena.com/news/enanta-stock-doubles-despite-rsv-trial-missing-primary-endpoint/
2. https://www.fiercebiotech.com/biotech/enanta-sees-rsv-drug-fail-phase-2b-finds-positives-secondaries-and-subgroups
4. https://insights.citeline.com/scrip/scrip/r-and-d/clinical-trials/enanta-plans-phase-iii-trial-of-zelicapavir-despite-primary-endpoint-miss-HPTI2V6KH5AAVJRTOSLYLKPLVI/