Acquisition Complements and Strengthens Merck’s Cardiovascular Pipeline

Sotatercept is a Potentially First-In-Class Therapy in Phase 3 Development for the Treatment of Pulmonary Arterial Hypertension

REBLOZYL ® (luspatercept-aamt) is a First-In-Class Erythroid Maturation Recombinant Fusion Protein Approved for the Treatment of Anemia in Certain Rare Blood Disorders

KENILWORTH, NJ & CAMBRIDGE, MA, USA I September 30, 2021 I Merck (NYSE: MRK), known as MSD outside the United States and Canada, and Acceleron Pharma Inc. (Nasdaq: XLRN), a publicly traded biopharmaceutical company, today announced that the companies 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.

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.”

Under the terms of the acquisition agreement, Merck, through a subsidiary, will initiate a tender offer to acquire all outstanding shares of Acceleron. The closing of the tender offer will be subject to certain conditions, including the tender of shares representing at least a majority of the total number of Acceleron’s outstanding shares, receipt of applicable regulatory approvals, and other customary conditions. Upon the successful completion of the tender offer, Merck’s acquisition subsidiary will be merged into Acceleron, and any remaining shares of common stock of Acceleron will be canceled and converted into the right to receive the same $180 per share price payable in the tender offer. The transaction is expected to close in the fourth quarter of 2021.

Merck Investor Call

Investors, journalists and the general public may access a live audio webcast of the call today at 8:00 a.m. EDT on Merck’s website at Institutional investors and analysts can participate in the call by dialing (833) 353-0277 or (469) 886-1947 and using ID code number 8698516. Members of the media are invited to monitor the call by dialing (833) 353-0277 or (469) 886-1947 and using ID code number 8698516. Journalists who wish to ask questions are requested to contact a member of Merck’s Media Relations team at the conclusion of the call.

About Sotatercept

Sotatercept is an investigational reverse-remodeling agent proposed to rebalance TGF-beta superfamily signaling. In preclinical models of PAH, sotatercept reversed pulmonary arterial wall and right ventricular remodeling that are hallmarks of the disease. A Phase 2 trial (PULSAR) evaluating sotatercept in combination with approved PAH-specific medicines in patients with PAH met its primary endpoint of improvement in pulmonary vascular resistance. The study results were published in the New England Journal of Medicine. Sotatercept is being studied in multiple Phase 3 trials for the treatment of certain patients with PAH as well as a Phase 2 trial in patients with combined post- and pre-capillary pulmonary hypertension in heart failure with preserved ejection fraction.

The United States Food and Drug Administration (FDA) has granted Orphan Drug and Breakthrough Therapy designations and the European Commission and European Medicines Agency (EMA) have granted Orphan and Priority Medicines (PRIME) designations, respectively, for sotatercept for the treatment of PAH.


Acceleron’s REBLOZYL (luspatercept-aamt) is the first and only erythroid maturation agent approved in the United States, Europe, Canada and Australia for the treatment of anemia in certain rare blood disorders. REBLOZYL is being developed as part of a global collaboration with Bristol Myers Squibb. Ongoing Phase 3 trials are evaluating luspatercept for the treatment of anemia in patient populations of myelodysplastic syndromes, beta-thalassemia, and myelofibrosis.

Credit Suisse Securities (USA) LLC and Goldman Sachs & Co. LLC acted as financial advisors to Merck in this transaction and Covington & Burling LLP and Gibson, Dunn & Crutcher LLP as its legal advisors. Centerview Partners LLC and J.P. Morgan Securities LLC were financial advisors to Acceleron and Ropes & Gray LLP its legal advisor.

About Merck

For over 130 years, Merck, known as MSD outside of the United States and Canada, has been inventing for life, bringing forward medicines and vaccines for many of the world’s most challenging diseases in pursuit of our mission to save and improve lives. We demonstrate our commitment to patients and population health by increasing access to health care through far-reaching policies, programs and partnerships. Today, Merck continues to be at the forefront of research to prevent and treat diseases that threaten people and animals – including cancer, infectious diseases such as HIV and Ebola, and emerging animal diseases – as we aspire to be the premier research-intensive biopharmaceutical company in the world. For more information, visit and connect with us on Twitter, Facebook, Instagram, YouTube and LinkedIn.

About Acceleron

Acceleron is a biopharmaceutical company dedicated to the discovery, development, and commercialization of therapeutics to treat serious and rare diseases. Acceleron’s leadership in the understanding of TGF-beta superfamily biology and protein engineering generates innovative compounds that engage the body’s ability to regulate cellular growth and repair. Acceleron focuses its research, development, and commercialization efforts in pulmonary and hematologic diseases. In pulmonary, Acceleron is developing sotatercept for the treatment of pulmonary hypertension (PH). Following positive PULSAR Phase 2 results, Acceleron is executing on its Phase 3 development plan to support its long-term vision of establishing sotatercept as a backbone key therapy for patients with PAH as an add-on to the current standard of care. Acceleron is also expanding the development of sotatercept into Group 2 PH, with the CADENCE Phase 2 trial expected to initiate this year. Acceleron has expanded its rare pulmonary disease pipeline and is investigating the potential of ACE-1334 in a Phase 1b/Phase 2 trial in systemic sclerosis-associated interstitial lung disease (SSc-ILD).

In hematology, REBLOZYL (luspatercept-aamt) is the first and only erythroid maturation agent approved in the United States, Europe, Canada and Australia for the treatment of anemia in certain blood disorders. REBLOZYL is part of a global collaboration partnership with Bristol Myers Squibb. The Companies co-promote REBLOZYL in the United States and are also developing luspatercept for the treatment of anemia in patient populations of myelodysplastic syndromes, beta-thalassemia and myelofibrosis.

For more information, please visit Follow Acceleron on Social Media: @AcceleronPharma and LinkedIn.

Important Information About the Tender Offer

The tender offer described in this press release has not yet commenced. This press release is for informational purposes only and is neither an offer to purchase nor a solicitation of an offer to sell any shares of the common stock of Acceleron Pharma Inc. (Acceleron) or any other securities, nor is it a substitute for the tender offer materials described herein. At the time the planned tender offer is commenced, a tender offer statement on Schedule (TO), including an offer to purchase, a letter of transmittal and related documents, will be filed by Merck Sharp & Dohme Corp. (“Merck”) and Astros Merger Sub, Inc., a wholly-owned subsidiary of Merck, with the Securities and Exchange Commission (the “SEC”), and a solicitation/recommendation statement on Schedule 14D-9 will be filed by Acceleron with the SEC.


Investors and security holders may obtain a free copy of the Offer to Purchase, the related Letter of Transmittal, certain other tender offer documents and the Solicitation/Recommendation Statement (when available) and other documents filed with the SEC at the website maintained by the SEC at or by directing such requests to the Information Agent for the Offer, which will be named in the tender offer statement. In addition, Merck and Acceleron file annual, quarterly and current reports and other information with the SEC, which are available to the public from commercial document-retrieval services and at the SEC’s website at Copies of the documents filed with the SEC by Merck may be obtained at no charge on Merck’s internet website at or by contacting Merck at 2000 Galloping Hill Road, Kenilworth, N.J. 07033 or (908) 423-1000. Copies of the documents filed with the SEC by Acceleron may be obtained at no charge on Acceleron’s internet website at or by contacting Acceleron at 128 Sidney Street, Cambridge, MA 02139 or (617) 649-9200.