KENILWORTH, N.J. — Merck and Acceleron Pharma have entered into a definitive agreement under which Merck, through a subsidiary, will acquire Acceleron for $180 per share in cash for an approximate total equity value of $11.5 billion, the companies said Thursday.

Acceleron is focused on harnessing the power of the transforming growth factor (TGF)-beta superfamily of proteins that is known to play a central role in the regulation of cell growth, differentiation and repair. Acceleron’s lead therapeutic candidate, sotatercept, has a novel mechanism of action with the potential to improve short-term and/or long-term clinical outcomes in patients with pulmonary arterial hypertension (PAH), a progressive and life-threatening blood vessel disorder. Sotatercept is in Phase 3 trials as add-on to current standard of care for the treatment of PAH.

“Strategic business development is a top priority for Merck as we look to drive sustainable growth and further bolster and balance our pipeline with breakthrough science,” said Rob Davis, chief executive officer and president, Merck. “Acceleron’s innovative research has yielded an exciting late-stage candidate that complements and strengthens our growing cardiovascular portfolio and pipeline and holds the potential to build upon Merck’s proud legacy in cardiovascular disease.”

In addition to sotatercept, Acceleron’s portfolio includes REBLOZYL^® (luspatercept-aamt), a first-in-class erythroid maturation recombinant fusion protein approved in the United States, Europe, Canada and Australia for the treatment of anemia in certain rare blood disorders. REBLOZYL is being developed and commercialized through a global collaboration with Bristol Myers Squibb.

“This agreement with Merck represents the culmination of decades of work by Acceleron researchers successfully leveraging our company’s deep scientific expertise in the biology of the TGF-beta superfamily and driven by an unwavering dedication to delivering life-changing medicines for patients,” said Habib Dable, chief executive officer and president, Acceleron. “We believe Merck is well-positioned to apply its industry-leading clinical and commercial capabilities to harness the potential of sotatercept as we join together to help make an impact on cardiopulmonary disease for the benefit of patients.”