Topline results were announced from a phase 3 study evaluating sotatercept, a potential first-in-class activin receptor type IIA-Fc fusion protein, for the treatment of pulmonary arterial hypertension (PAH).

In the STELLAR trial ( Identifier: NCT04576988), patients with PAH (WHO Group 1) were randomly assigned to receive sotatercept or placebo administered subcutaneously every 21 days, as an add-on to background PAH therapy. The primary endpoint of the study was exercise capacity, as measured by the change from baseline in 6-minute walk distance (6MWD) at 24 weeks.

Results showed a statistically significant and clinically meaningful improvement in 6MWD among patients treated with sotatercept when compared with placebo. Sotatercept was also associated with statistically significant improvements in 8 out of 9 secondary outcome measures, including the proportion of participants achieving multicomponent improvement (defined as improvement in 6MWD, improvement in N-terminal pro-B-type natriuretic peptide level, and either improvement in WHO functional class [FC] or maintenance of WHO FC II), and the outcome measure of time to death or the first occurrence of a clinical worsening event. An assessment of the Cognitive/Emotional Impacts domain score of PAH-SYMPACT® did not result in a statistical significant change.

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“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.”

Sotatercept was previously granted Breakthrough Therapy designation by the Food and Drug Administration (FDA). “We are moving with urgency on our regulatory applications to bring this investigational therapy to these patients,” noted Dr Li in the Company press release.

Additional data from the STELLAR trial will be presented at an upcoming scientific congress.


Merck announces positive top-line results from pivotal phase 3 STELLAR trial evaluating sotatercept for the treatment of adults with pulmonary arterial hypertension (PAH). News release. October 10, 2022. Accessed October 11, 2022.

This article originally appeared on MPR