Acceleron Pharma Expands Management Team with Two New Appointments

Key Personnel Support Growth and Advancement of Clinical Pipeline and GMP Manufacturing Activities

CAMBRIDGE, Mass. - December 22, 2009 - Acceleron Pharma, Inc., a biopharmaceutical company developing novel therapeutics that modulate the growth of cells and tissues including red blood cells, bone, muscle, fat, and the vasculature, today announced the expansion of its management team with two newly created key positions. The Company named Melissa Morandi as Vice President of Quality and Kenneth Attie, M.D. as Vice President of Medical Research.

“Acceleron now has three internally discovered, developed and manufactured drugs in clinical trials and several more in preclinical development”, said John Knopf, Ph.D., Co-founder and Chief Executive Officer of Acceleron. “I’m delighted that Melissa and Ken have joined Acceleron as both these professionals have the experience and proven track records in their respective areas of expertise that will support the successful growth and advancement of our pipeline.”

Ms. Melissa Morandi joins Acceleron from Anesiva, Inc., where she was Vice President of Quality. Previously, Melissa has held numerous leadership positions in Quality Departments at Biogen Idec, Inc., Genentech and Amgen. During her 9-year tenure at Genentech, Melissa supported product launches and regulatory inspections for Genentech's oncology, cardiac and growth hormone products. Prior to that, Melissa worked in Quality Assurance at Amgen, where she supported product launches for several Amgen products. Melissa is Regulatory Affairs Certified (R.A.C.) and is currently a board member for the West Coast Parenteral Drug Association. Melissa holds a B.A. degree from the University of California at Santa Barbara and a M.S. degree in Immunology from California State University at Northridge.

Dr. Kenneth Attie comes to Acceleron with more than 20 years of experience in the biotech industry and academic research. He joins Acceleron from Altus Pharmaceuticals, where he was Vice President of Clinical Development and Medical Affairs. Previously, Ken was Chief Medical Officer at Insmed, where he was responsible for obtaining FDA approval and commercialization of an IGF-1-related product. Prior to that, Ken held numerous positions during his 12-year tenure at Genentech, where he was responsible for several phase I-IV studies and participated in 9 FDA submissions for growth hormone. Ken was Assistant Clinical Professor of Pediatrics at the University of California San Francisco Medical Center, is board-certified in Pediatrics and Pediatric Endocrinology, and has more than 40 publications in peer-reviewed journals. He received his M.D. degree from New York University Medical Center and received his B.A. (in Music) from the University of Michigan, Ann Arbor.

About Acceleron

Acceleron is a privately held biopharmaceutical company committed to discover, develop, manufacture and commercialize novel biotherapeutics that modulate the growth of red blood cells, 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 TGF-ß superfamily of proteins. ACE-011 is currently being studied in two Phase 2 clinical trials in cancer patients. ACE-031 is currently being studied in a Phase 1 clinical trial in healthy volunteers and ACE-041 is being studied in a Phase 1 clinical trial in patients with advanced cancer. In addition, the company is developing several other new product candidates that increase muscle mass, control angiogenesis, inhibit fat accumulation and increase bone mass and strength. 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 include Advanced Technology Ventures, Alkermes, Bessemer Ventures, Celgene, 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

Mariesa Kemble (Media)
Suda Communications LLC, 608-850-4745