Enanta Pharmaceuticals, Inc. (NASDAQ: ENTA) on Monday released topline data from RSVHR Phase 2b study of zelicapavir in outpatient adults with acute respiratory syncytial virus (RSV) infection who are at high risk of complications, including the elderly and/or those with congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD) or asthma.

Zelicapavir, which received Fast Track designation from the U.S. Food and Drug Administration (FDA), is a novel N-protein inhibitor in development as a once-daily oral treatment for RSV. 

The proof-of-concept study was designed to understand the antiviral treatment effect on symptom endpoints measured using the Respiratory Infection Intensity and Impact Questionnaire (RiiQ) patient-reported outcome tool and other clinically meaningful endpoints in a broad patient population.

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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 ≥75, termed the HR3 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 (LRTD) 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 (PGI-S) score, with a statistically significant 2-day faster resolution with zelicapavir compared to placebo. A lower hospitalization rate was observed for patients treated with zelicapavir than with placebo.

The study met key secondary virology endpoints showing a robust antiviral effect.

A total of 186 subjects received 800mg of zelicapavir (n=121) or placebo (n=65) orally, once daily for 5 days, and were evaluated for 28 days thereafter (safety population).

Zelicapavir demonstrated a favorable safety profile over the initial 5-day dosing period and through 28 days of follow-up, with adverse events (AEs) being similar between zelicapavir and placebo.

“We are highly encouraged by these results from our Phase 2b trial of zelicapavir in high-risk adults infected with RSV. This represents the first time an RSV antiviral treatment has demonstrated a clinically meaningful benefit in these high-risk adult outpatients. These data demonstrate the potential for zelicapavir to reduce the duration of RSV symptoms in high-risk adults who face an increased risk of hospitalization or death from this virus,” said Scott T. Rottinghaus, M.D., Chief Medical Officer of Enanta Pharmaceuticals. 

Price Action: ENTA stock was trading higher by 43.42% to $11.33 at last check Monday.

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