FDA Expands Approval of Merck's WINREVAIR After Study Shows 76% Drop in PAH Death and Hospitalization Risk

Author: Benzinga Newsdesk | October 27, 2025 06:47am

Merck (NYSE:MRK), known as MSD outside the United States and Canada, today announced that the U.S. Food and Drug Administration (FDA) has approved an update to the U.S. product label based on the Phase 3 ZENITH trial for WINREVAIR™ (sotatercept-csrk) for injection, 45mg, 60mg. WINREVAIR, an activin signaling inhibitor, is now FDA-approved for the treatment of adults with pulmonary arterial hypertension (PAH, WHO Group 1 pulmonary hypertension) to improve exercise capacity and WHO functional class (FC), and reduce the risk of clinical worsening events, including hospitalization for PAH, lung transplantation and death. WINREVAIR was initially approved based on the pivotal STELLAR study in March 2024. Today's approval expanded the indication of WINREVAIR to include components of the clinical worsening events: hospitalization for PAH, lung transplantation and death.

In ZENITH (N=172; 86 WINREVAIR, 86 placebo), adding WINREVAIR to background therapy demonstrated a statistically significant and clinically meaningful 76% reduction in the risk of major morbidity and mortality outcomes in adults with PAH WHO functional class III or IV compared to placebo (HR: 0.24; 95% CI: 0.13, 0.43; p<0.0001). The trial's composite primary efficacy endpoint events — time to first occurrence of all-cause death, lung transplantation or PAH-worsening hospitalization of ≥24 hours — occurred in 15 WINREVAIR-treated participants (17%) versus 47 placebo-treated participants (55%). Due to overwhelming efficacy based on the primary endpoint result, the ZENITH trial was stopped early at the interim analysis and patients were offered the opportunity to receive WINREVAIR through an open-label long-term follow-up study.

Posted In: MRK