Enanta Stock Surges 91% on Mixed RSV Drug Trial Results
Investors focus on positive secondary data, including lower hospitalization rates, overlooking the study's missed primary goal.
Enanta Pharmaceuticals (NASDAQ: ENTA) shares skyrocketed as much as 91.9% on Wednesday in a stunning rally fueled by clinical trial data for its respiratory syncytial virus (RSV) treatment, zelicapavir. The dramatic investor enthusiasm came despite the drug technically failing to meet its primary endpoint in a mid-stage study, as a host of positive secondary outcomes offered a clear path forward for the antiviral candidate.
The Phase 2b RSVPEDs study was designed to evaluate zelicapavir in high-risk adult patients with RSV. While the trial did not achieve its main goal of reducing the time to resolution of lower respiratory tract disease symptoms, investors quickly looked past the headline result to more compelling metrics within the data. , patients treated with zelicapavir saw a 2.2-day faster resolution of all 13 RSV symptoms compared to those receiving a placebo.
More importantly, the treatment demonstrated a significant impact on severe outcomes. The study revealed a much lower hospitalization rate of just 1.7% in the zelicapavir arm, a stark contrast to the 5.0% rate observed in the placebo group. This reduction is a critical data point for a virus that poses a serious threat to older adults and individuals with underlying health conditions. The drug also showed a powerful antiviral effect, with a median time to undetectable viral load that was four to five days faster than placebo.
Following the news, as the market priced in a renewed outlook for the drug's potential. Enanta management confirmed it plans to use the results to design a Phase 3 trial, having identified multiple potential registrational endpoints. Zelicapavir has already received Fast Track designation from the U.S. Food and Drug Administration (FDA), a status intended to expedite the review of drugs that treat serious conditions. Investors are betting that the strength of the secondary data provides a viable pathway to approval and commercialization.