Merck (NYSE:MRK), known as MSD outside of the United States and Canada, announced today positive topline results from the Phase 3 ZENITH study evaluating WINREVAIR (sotatercept-csrk) in adults with pulmonary arterial hypertension (PAH, WHO* Group 1) functional class (FC) III or IV at high risk of mortality. ZENITH met its primary endpoint of time to first morbidity or mortality event (all-cause death, lung transplantation, or PAH worsening related hospitalization of ≥ 24 hours). In the study, WINREVAIR demonstrated a statistically significant and clinically meaningful reduction in the risk of morbidity or mortality events compared to placebo, both on top of background PAH therapy. Based on the strength of these results, an independent data monitoring committee has recommended ZENITH be stopped early and all participants be offered the opportunity to receive WINREVAIR through the SOTERIA open-label extension study. In preliminary assessment, adverse events and serious adverse events were balanced between the treatment groups.

"PAH is a serious, progressive disease with a high incidence of morbidity and mortality," said Dr. Eliav Barr, senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories. "Based on the primary endpoint demonstrating overwhelming efficacy, all ZENITH study participants will be offered the opportunity to receive WINREVAIR. These findings are impressive, set a high evidentiary bar for studies of future candidates developed for the treatment of PAH and support the potential of WINREVAIR to be practice-changing in the management of PAH."

"The ZENITH trial was designed to evaluate whether the addition of WINREVAIR, an activin signaling inhibitor, could reduce the risk of death, lung transplantation, or PAH hospitalizations for patients living with advanced PAH," said Dr. Vallerie McLaughlin**, Kim A Eagle MD Endowed Professor of Cardiovascular Medicine and Director, Pulmonary Hypertension Program, University of Michigan in Ann Arbor. "This is the first study in PAH in which the interim analysis led to an early conclusion of the study due to overwhelming efficacy. WINREVAIR has brought significant optimism to the field, and we thank the investigators and patients for being part of this important study."

WINREVAIR is currently approved in the U.S. and 36 countries based on the results from the Phase 3 STELLAR trial. Most recently, in November of this year, WINREVAIR was submitted for approval in Japan based on the STELLAR trial and results from an open-label Phase 3 study in Japanese patients.

Results from ZENITH will be presented at an upcoming medical meeting and will be submitted to regulatory authorities.