Acceleron Pharma Presents Findings of ACE-536, a Novel Red Blood Cell-Forming Agent, at the 51st Annual Meeting of the American Society of Hematology

Company Discovers Novel Mechanism to Increase Red Blood Cells

CAMBRIDGE, Mass.--(BUSINESS WIRE)--Dec 8, 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, presented data demonstrating that ACE-536 promotes formation of red blood cells through inhibition of members of the TGF-beta superfamily, at the 51st Annual Meeting of the American Society of Hematology.

“This discovery is a paradigm shift in our understanding of the red blood cell growth and differentiation process,” said Jasbir Seehra, Ph.D., Chief Scientific Officer of Acceleron Pharma. “For the last 30 years, the treatment of anemia has been limited to iron supplementation and recombinant erythropoietin (EPO). We have shown that ACE-536 stimulates red blood cell production through an entirely unique mechanism.”

The study findings demonstrate that administration of ACE-536 promotes rapid, dose-dependent increases of hemoglobin, hematocrit, and red blood cells in several animal species. In addition, treatment with ACE-536 corrects anemia in animal models of chronic kidney disease and acute blood loss. The studies also show that ACE-536 promotes red blood formation in the absence of EPO signaling, through an independent pathway. Moreover, ACE-536 has distinct effects from EPO on red blood cell differentiation, and acts on a different population of progenitor blood cells during a later phase of red blood cell development.

About ACE-536

ACE-536 is a novel ligand trap that binds to and prevents signaling of red blood cell growth and differentiation factors (GDFs) that are members of the TGF-β superfamily of proteins. Acceleron is developing ACE-536 for the treatment of anemia and plans to enter clinical trials in the first half of 2010.

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-β 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.

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

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