Enanta Pharmaceuticals has announced positive topline results from its Phase 2 clinical trial of zelicapavir, an antiviral drug, for the treatment of respiratory syncytial virus (RSV) in pediatric patients. The study, known as RSVPEDs, enrolled children aged 28 days to 36 months, both hospitalized and non-hospitalized, to assess the antiviral effects of zelicapavir.
Zelicapavir Demonstrates Antiviral Activity
The Phase 2 trial (RSVPEDs) included 96 subjects, with 70 receiving zelicapavir and 26 receiving a placebo. Baseline characteristics and demographics were consistent across treatment groups, with the majority of subjects being hospitalized upon enrollment. According to Enanta Pharmaceuticals, a subset of subjects who initiated treatment within three days of symptom onset experienced a 1.2 log decline in viral load, indicating a rapid antiviral response. Zelicapavir also achieved the targeted drug exposure levels across all age groups and dosing cohorts.
Symptom Reduction and Safety Profile
While the REspiratory Syncytial VIrus NETwork (ReSViNET) tool showed no significant difference in symptom reduction between the treatment and placebo groups, the RESpiratory ObservabLE Reported Outcome-Paediatric (RESOLVE-P) tool indicated a trend towards greater symptom reduction in subjects treated with zelicapavir. The drug was well-tolerated, with a favorable safety profile compared to placebo.
Dosing and Assessment Methods
Subjects aged 28 days to 12 months were administered 5mg/kg of zelicapavir, while those aged 12-36 months received a 7.5mg/kg dose. The study utilized the ReSViNET and RESOLVE-P tools to assess symptoms, addressing the lack of validated symptom assessment tools for pediatric RSV.
Company Perspective
Enanta Pharmaceuticals' chief medical officer, Scott Rottinghaus, stated, “We are excited to share these positive results from our first-in-paediatric Phase II study of zelicapavir, which we believe confirm a strong profile for our lead RSV antiviral and strengthen Enanta’s position as a leader in developing treatments for RSV. Zelicapavir demonstrated an antiviral effect on both primary endpoints, as well as secondary virology endpoints.”
About Zelicapavir
Zelicapavir, Enanta’s lead N-protein inhibitor, is being developed for the treatment of RSV infection and has been granted Fast Track designation by the U.S. Food and Drug Administration. It functions as a nanomolar inhibitor of both RSV-A and RSV-B activity. Unlike RSV fusion inhibitors, zelicapavir targets the virus’ replication machinery and has demonstrated a high barrier to resistance in vitro. Preclinical studies have shown that zelicapavir maintains antiviral potency across all clinical isolates tested and is active against viral variants resistant to other mechanisms. The drug has also demonstrated a favorable safety, pharmacokinetic, and drug-drug interaction profile in a Phase 1 program. Currently, zelicapavir is being evaluated in RSVHR, a Phase 2b study in the elderly and/or those with congestive heart failure, chronic obstructive pulmonary disease (COPD), or asthma.
