Merck’s Winrevair™ Gains FDA Priority Review Following Stellar ZENITH Trial Data

Merck has revealed that the U.S. Food and Drug Administration (FDA) has accepted and granted priority review for a supplemental Biologics License Application (sBLA) for Winrevair™ (sotatercept-csrk). This application aims to broaden the drug’s label, supported by robust data from the Phase 3 ZENITH trial targeting advanced, life-threatening outcomes in pulmonary arterial hypertension (PAH), WHO Group 1. Initially approved by the FDA in March 2024, Winrevair, a pioneering activin signaling inhibitor, is currently used to enhance exercise capacity, improve functional class, and slow disease progression in PAH patients on standard therapies.

The ZENITH trial delivered striking evidence that Winrevair exceeds mere symptom relief. It achieved a 76% reduction in the risk of clinical worsening or death—a composite endpoint encompassing death, lung transplant, PAH-related hospitalization, or the need for additional PAH therapy—compared to placebo. The trial’s early termination for efficacy, recommended by an independent data monitoring committee, highlights the significance of these results, marking a major leap forward in PAH treatment, a progressive and often lethal condition affecting lung arteries and straining the heart.

ZENITH stood out as the first Phase 3 PAH clinical trial to prioritize morbidity and mortality over symptom management or functional gains. It included over 320 adult PAH patients on background therapies such as endothelin receptor antagonists, phosphodiesterase type 5 inhibitors, and/or prostacyclin pathway agents. Participants continued their existing treatments and were randomly assigned to receive either Winrevair or placebo. The trial’s premature conclusion due to evident benefits underscores the urgency and strength of the findings.

Under the FDA’s Priority Review program, which accelerates the standard 10-month review to 6 months, Merck’s sBLA is being evaluated. This reflects the agency’s recognition of the drug’s potential to surpass existing treatments, with a decision anticipated by the PDUFA (Prescription Drug User Fee Act) date of October 25, 2025.

Dr. Joerg Koglin, Senior Vice President of Global Clinical Development at Merck Research Laboratories, expressed enthusiasm, noting that many PAH patients remain at risk despite current treatments. He described the ZENITH data as a “significant step forward” in addressing unmet needs. An approved label update would highlight Winrevair’s broader clinical impact, including its ability to substantially lower hospitalization or death risks in high-risk patients.

Winrevair maintained a manageable safety profile in the ZENITH trial, with common side effects including elevated hemoglobin and reduced platelet counts, consistent with prior studies like the STELLAR trial. No new safety concerns arose, and participants completing ZENITH can join the SOTERIA long-term extension study.

Winrevair is now approved in over 45 countries, including the EU, Canada, and Japan, based on earlier trial successes. Merck continues to expand its clinical research for sotatercept to explore its potential in pulmonary hypertension and other cardiovascular conditions.

Should the updated label be approved, it could reshape clinical practice by establishing Winrevair as both a functional and life-saving therapy, shifting PAH management toward survival and long-term stability rather than symptom control alone.

This development offers hope to thousands of PAH patients globally, who face a debilitating and life-shortening disease with limited long-term options.