MSD, also known in the United States and Canada as Merck (NYSE: MRK), announced today the U.S. Food and Drug Administration (FDA) has granted approval for sotatercept-csrk (U.S. Brand Name: WINREVAIR™, for injection, 45mg, 60mg) for treating adults with pulmonary arterial hypertension (PAH, World Health Organization [WHO] Group 1). This approval aims to increase exercise capacity, enhance WHO functional class (FC), and reduce the risk of clinical worsening events. WINREVAIR, having earned Breakthrough Therapy Designation by the FDA earlier, is the pioneering FDA-approved activin signaling inhibitor therapy for PAH. It represents a novel therapy class that operates by rebalancing pro- and anti-proliferative signaling, thereby managing vascular cell proliferation fundamental to PAH.

“Pulmonary arterial hypertension is a rare, progressive, and ultimately fatal disease characterized by the thickening and narrowing of lung blood vessels, exerting excessive strain on the heart,” said Dr. Marc Humbert, Professor of Medicine and Director of the Pulmonary Hypertension Reference Center at Université Paris-Saclay and a Phase 3 STELLAR study investigator. “The Phase 3 STELLAR trial results, which demonstrate significant clinical benefits of adding WINREVAIR to standard PAH therapy over standard therapy alone, mark a significant advancement in treating this condition. This approval introduces a unique therapeutic alternative that targets a new pathway in PAH treatment.”

The approval is founded on the Phase 3 STELLAR trial outcomes, comparing WINREVAIR (n=163) against placebo (n=160), each combined with standard care therapies in adult PAH patients (WHO Group 1 FC II or III). The study showed that integrating WINREVAIR with standard therapy notably increased six-minute walk distance from baseline by 41 meters (95% CI: 28, 54; p<0.001; placebo-adjusted) at Week 24, along with significant improvements in several important secondary outcomes, such as an 84% reduction in the risk of death from any cause or PAH clinical worsening events versus standard therapy alone (number of events: 9 vs 42, hazard ratio=0.16; 95% CI: 0.08, 0.35; p<0.001).

Before each dose of WINREVAIR for the initial 5 doses, and periodically thereafter, healthcare providers are advised to monitor hemoglobin and platelet counts to determine if dosage adjustments are needed. WINREVAIR has the potential to increase hemoglobin, possibly leading to erythrocytosis, which, if severe, may heighten the risk of thromboembolic events or hyperviscosity syndrome. Additionally, WINREVAIR may decrease platelet count, resulting in severe thrombocytopenia and increased bleeding risk; this condition occurred more frequently in patients also receiving prostacyclin infusion. Treatment initiation is contraindicated if platelet count falls below 50,000/mm3. Further Selected Safety Information is available below.

Matt Granato, president and CEO of the Pulmonary Hypertension Association, expressed enthusiasm about the development of new treatments for PAH patients, highlighting the disease's life-altering impact and the limiting symptoms patients endure. This approval signifies progress in PAH research and offers a novel treatment pathway for patients.

Dr. Aaron Waxman, Executive Director of the Center for Pulmonary Heart Diseases at Brigham and Women’s Hospital and a Phase 3 STELLAR study investigator, emphasized the ongoing need for PAH treatments that address critical clinical objectives, such as enhancing exercise capacity and functional class. He highlighted the potential of sotatercept added to standard therapy to establish a new care standard for PAH patients.

Administered via subcutaneous injection every three weeks, WINREVAIR can be self-administered by patients or caregivers under healthcare provider guidance, training, and follow-up. For proper preparation and administration details, refer to the Instructions for Use. MSD anticipates WINREVAIR will be available in select U.S. specialty pharmacies by the end of April.

Dr. Eliav Barr, senior vice president and head of global clinical development, chief medical officer at MSD Research Laboratories, remarked on the approval