Enanta RSV antiviral flops mid-stage trial

May 19, 2022

Enanta Pharmaceuticals reported disappointing top-line results for its phase 2b study evaluating its potent N-protein inhibitor in otherwise healthy adults with respiratory syncytial virus (RSV).

The study, which evaluated the Massachusetts-based biotech's EDP-938 in 81 low-risk patients dosed with RSV, failed to meet both primary and secondary endpoints. According to Enanta, the treatment failed to reduce total symptom score compared to placebo and also did not hit secondary antiviral endpoints either.

It's an unfortunate stumble for Enanta in the increasingly competitive race for RSV treatments and vaccines. Last month, competitor Ark Bio reported that its treatment candidate, ziresovir, was the first antiviral drug to successfully complete a pivotal phase 3 study in children hospitalized with RSV. Around that time, Pfizer snatched up ReViral and its RSV therapeutic candidates, including sisunatovir, which already has a successful phase 2 challenge trial under its belt and is currently in phase 2 clinical development in infants.

Most recently on the vaccine front, Moderna launched phase 3 trials for its mRNA RSV vaccine in late Feb., aiming to enroll approximately 34,000 candidates aged 60 years and older from multiple countries. Moderna's end goal is a potential combination vaccine that could offer protection against COVID-19, influenza and RSV

As for EDP-938, Enanta isn't throwing in the towel quite yet. The company highlighted a "statistically significant difference in the number of subjects achieving undetectable RSV RNA at the end of treatment with EDP-938" and said it expects to achieve better results when it tests the treatment in high risk populations.