By Fineline Cube 
US pharmaceutical giant Merck, Sharp & Dohme (MSD; NYSE: MRK) announced that the US Food and Drug Administration (FDA) has accepted its market filing for Winrevair (sotatercept) for priority review. Winrevair, an activin signaling inhibitor, was initially approved in 2024 for treating adult pulmonary arterial hypertension (PAH, WHO Group 1) to improve exercise capacity, enhance WHO functional class (FC), and reduce the risk of clinical worsening events.
Phase III ZENITH Study Results
The filing leveraged results from the Phase III ZENITH study, a global, double-blind, placebo-controlled trial. The study evaluated Winrevair as add-on therapy to maximal tolerated background PAH treatment in adults with WHO FC III/IV PAH. It used a novel primary endpoint of time to first occurrence of all-cause death, lung transplant, or PAH-related hospitalization lasting ≥24 hours.
Trial Significance and Outcomes
ZENITH is the first PAH Phase III study with a primary endpoint exclusively comprising major morbidity/mortality events. It is also the first PAH Phase III trial concluded early by an independent data monitoring committee due to overwhelming efficacy. Results showed Winrevair achieved a 76% risk reduction in the composite endpoint versus placebo, with early clinical benefits that increased over time and a safety profile consistent with previous studies.-Fineline Info & Tech