Acceleron Pharma Acknowledged for Positive Impact on Economic Development in Massachusetts

CAMBRIDGE, Mass. – September 22, 2008 - Acceleron Pharma, Inc., a biopharmaceutical company developing novel therapeutics that modulate the growth of tissues including bone and muscle, announced that the company is a finalist in the Greater Boston region for the Fifth Annual Team Massachusetts Economic Impact Award presented by the Massachusetts Alliance for Economic Development. This award recognizes companies from across the Commonwealth for their outstanding contributions to the Massachusetts economy. The other finalists in the Greater Boston region are Brigham and Woman’s Hospital, CSN Stores, JPMorgan Chase, Microsoft and Shire Pharmaceuticals.

Acceleron recently announced that it will be increasing its headcount 40% by hiring staff across essentially all functions in 2008. Furthermore, the company leased an additional 37,500 sq. ft. of administrative, laboratory and manufacturing space doubling its presence in Cambridge. In this new space, Acceleron will build its second GMP protein manufacturing facility. This growth in headcount and facilities runs parallel to the advancement of the company’s expanding pipeline.

Acceleron expects to begin a phase 2a study in Multiple Myeloma with its lead compound, ACE-011 at the beginning of the fourth quarter and will present encouraging ACE-011 clinical results at scientific meetings later this year. The company also plans to initiate the first clinical trial with its ACE-031 program for increasing skeletal muscle mass and strength in the next few months.

The Massachusetts Alliance for Economic Development (MAED) is a private, non-profit partnership of business, industry leaders, and government dedicated to fostering economic growth in the Commonwealth. Economic Impact Award finalist companies were selected based on their job growth, facility expansion, and investment since January 1, 2007, as well as other factors including community involvement.

About Acceleron

Acceleron is a privately held biopharmaceutical company committed to discover, develop, manufacture and commercialize novel biotherapeutics that modulate the growth of bone, muscle, fat and the vasculature to treat musculoskeletal, metabolic and cancer-related diseases. Acceleron’s scientific approach takes advantage of its unique insight into the regenerative powers of the Growth and Differentiation Factor (GDF) family of proteins. ACE-011, a novel bone forming agent, is the Company’s lead program and is being developed to reverse bone loss in diseases such as cancer-related bone loss. In addition, the company is advancing through preclinical development product candidates that increase muscle mass, control angiogenesis and inhibit fat accumulation. Acceleron utilizes proven biotherapeutic technologies and capitalizes on the company’s internal GMP manufacturing capability to rapidly and efficiently advance its therapeutic programs. The investors in Acceleron are Advanced Technology Ventures, Bessemer Ventures, Flagship Ventures, MPM BioEquities, OrbiMed Advisors, Polaris Ventures, QVT Financial, Sutter Hill Ventures and Venrock. For more information, visit www.acceleronpharma.com.

CONTACT:
Acceleron Pharma:
Steven Ertel, 617-649-9234
Vice President, Corporate Development

Paul Kidwell (Media)
Suda Communications LLC, tel: 617-296-3854

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