**Merck's WINREVAIR Achieves Major Milestone in PAH Treatment**

Merck & Co., Inc. (NYSE: MRK), also known as MSD outside the USA and Canada, has announced a significant breakthrough in the fight against pulmonary arterial hypertension (PAH). The company revealed positive topline results from its Phase 3 ZENITH study investigating WINREVAIR (sotatercept-csrk). Designed for adults with advanced PAH risk profile (WHO Group 1) functional class (FC) III or IV, ZENITH successfully met its primary endpoint of reducing the time to the first morbidity or mortality event, prompting an early termination of the study for efficacy reasons.

The ZENITH trial's independent data monitoring committee recommended stopping the study early due to the overwhelming efficacy demonstrated by WINREVAIR, which showed a statistically significant and clinically meaningful reduction in morbidity or mortality events compared to placebo. Merck plans to offer WINREVAIR to all study participants via the open-label SOTERIA extension study. Preliminary safety assessments showed balanced adverse events between treatment groups.

Dr. Eliav Barr, Merck's head of global clinical development and chief medical officer, applauded the study's outcomes, emphasizing the potential shift WINREVAIR could bring to PAH treatment standards. Dr. Vallerie McLaughlin, an investigator in the study, echoed this optimism, lauding the study's conclusive results as a landmark achievement and expressing gratitude to the participants and researchers involved.

Currently approved in the U.S. and 36 other nations based on the Phase 3 STELLAR trial, WINREVAIR is under review in Japan. The ZENITH study's findings will be presented at a future medical meeting and submitted to regulatory bodies.

The ZENITH trial, a global, double-blind, placebo-controlled study, enrolled 172 participants and aimed to evaluate WINREVAIR's efficacy in reducing severe PAH-related outcomes. Participants were randomly assigned in a 1:1 ratio to receive either WINREVAIR with background PAH therapy or a placebo. Secondary measures included overall and transplant-free survival.

Designed as an activin signaling inhibitor, WINREVAIR is FDA-approved to enhance exercise capacity, improve functional class, and mitigate clinical worsening events in PAH patients. The potential for serious adverse reactions necessitates careful monitoring, particularly regarding hemoglobin levels, platelet counts, and bleeding risks.

PAH, a rare and progressive disorder affecting approximately 40,000 individuals in the U.S., leads to significant heart strain, limited physical activity, and a five-year mortality rate of about 43%. Merck remains committed to leveraging advanced science to develop innovative health solutions aimed at improving global health outcomes.