Enanta reports ‘positive’ results from Phase 2b study of zelicapavir

Enanta (ENTA) Pharmaceuticals announced positive topline data from RSVHR, a Phase 2b, randomized, double-blind, placebo-controlled study to evaluate the efficacy and safety of zelicapavir in outpatient adults with acute RSV infection who are at high risk of complications including the elderly and/or those with congestive heart failure, chronic obstructive pulmonary disease or asthma. Zelicapavir, which received Fast Track designation from the U.S. FDA, is a novel N-protein inhibitor in development as a once-daily oral treatment for RSV. This proof-of-concept study was designed to understand the antiviral treatment effect on symptom endpoints measured using the Respiratory Infection Intensity and Impact Questionnaire patient reported outcome tool, as well as other clinically meaningful endpoints, in a broad patient population. A clinically meaningful improvement in time to complete resolution of all 13 RSV symptoms was observed for zelicapavir compared to placebo, with a benefit of 2.2 days for the overall efficacy population and 6.7 days for patients with CHF, COPD or age greater than or equal to 75, termed the HR3 population, which comprised the majority (81%) of the efficacy population. Zelicapavir also showed an improvement in time to complete resolution on the 29-parameter total RiiQ symptom scale of 3.6 days for the efficacy population and 7.2 days for the HR3 population compared to placebo. Additionally, there was a 3.0-day faster time to complete resolution of lower respiratory tract disease symptoms in the HR3 population; however, no effect was observed on the time to resolution of the LRTD subset of four symptoms to mild, which was the primary endpoint. The study met the secondary endpoint of time to improvement in the Patient Global Impression of Severity score, with a statistically significant 2-day faster resolution with zelicapavir compared to placebo. Importantly, a lower hospitalization rate was observed for patients treated with zelicapavir compared to placebo. The study met key secondary virology endpoints showing a robust antiviral effect. The study also showed that zelicapavir demonstrated a favorable safety profile and was well-tolerated.