Pharmaceutical giant Merck is acquiring Acceleron Pharma, which is testing a potentially new add-on treatment for pulmonary arterial hypertension (PAH). The $11.5 billion deal is expected to close by year end.

Acceleron’s sotatercept could block dysfunctional cell signaling and reverse abnormal blood vessel changes associated with PAH. Sotatercept is in Phase 3 of several clinical studies for PAH.

Sotatercept showed improved pulmonary-vascular, cardiovascular and exercise-related outcomes among participants in a 2018-2019 Phase 2 study, which assessed the drug’s safety and efficacy. The participants were already taking FDA-approved PAH medications, including prostacyclin infusion therapy.

Results of the study were published in the April 21, 2021, issue of the New England Journal of Medicine.

A Phase 2 trial to assess sotatercept for Group 2 pulmonary hypertension is expected to begin by year end.

Learn about active sotatercept trials on the Pulmonary Hypertension Association’s Clinical Trial Finder .