Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced positive top-line results from the pivotal Phase 3 STELLAR trial evaluating the safety and efficacy of sotatercept, an investigational activin receptor type IIA-Fc (ActRIIA-Fc) fusion protein being evaluated as an add-on to stable background therapy for the treatment of pulmonary arterial hypertension (PAH) (WHO Group 1). The trial met its primary efficacy outcome measure, demonstrating a statistically significant and clinically meaningful improvement in 6-minute walk distance (6MWD, which measures how far patients can walk in 6 minutes) from baseline at 24 weeks. Eight of nine secondary efficacy outcome measures achieved statistical significance, including the outcome measure of proportion of participants achieving multicomponent improvement (defined as improvement in 6MWD, improvement in N-terminal pro-B-type natriuretic peptide (NT-proBNP) level, and either improvement in WHO FC or maintenance of WHO FC II), and the outcome measure of time to death or the first occurrence of a clinical worsening event (TTCW). The Cognitive/Emotional Impacts domain score of PAH-SYMPACT®, which was assessed as the ninth and final secondary outcome measure, did not achieve statistical significance. The overall safety profile of sotatercept in STELLAR was in general consistent with what has been observed in Phase 2. Results from the study will be presented at an upcoming scientific congress.
“In the Phase 3 STELLAR study, sotatercept added to currently approved background therapy showed a profound effect on the primary efficacy outcome measure of improvement from baseline to 24 weeks in six-minute walk distance. The results from the secondary efficacy outcomes, including a favorable benefit seen in patients’ time to a clinical-worsening event, are especially noteworthy,” said Dr. Dean Y. Li, president, Merck Research Laboratories. “We believe that in totality, the results observed in the STELLAR study suggest that sotatercept has the potential to transform the treatment of patients with PAH. We are moving with urgency on our regulatory applications to bring this investigational therapy to these patients.”