Acceleron Pharma to Present ACE-011 Bone Growth Data at the ASBMR 29th Annual Meeting

CAMBRIDGE, MA – August 6, 2007 - Acceleron Pharma, Inc., a biopharmaceutical company developing novel therapeutics that modulate the growth of tissues including bone and muscle, today announced it will present the final results for the phase 1 clinical trial of ACE-011, its novel anabolic therapy for the treatment of bone loss at The American Society for Bone and Mineral Research (ASBMR) 29th Annual Meeting to be held in Honolulu, Hawaii, USA, September 16 – 19, 2007. The oral presentation is titled, “A Single Dose of ACE-011 Is Associated with Increases in Bone Formation and Decreases in Bone Resorption Markers in Healthy, Postmenopausal Women”, and will be presented on Tuesday September 18, 2007 at 11:15-11:30 a.m. in Kalakaua Ballroom AB, Hawaii Convention Center. This presentation represents the first time clinical data for an activin antagonist, a novel mechanism for an anabolic bone agent, will be presented at a scientific meeting.

About ACE-011

ACE-011, a protein therapeutic based on the activin receptor type IIA, is a novel anabolic agent that is expected to begin phase 2 clinical trials in Q4 2007. In numerous preclinical models of bone loss, ACE-011 has demonstrated beneficial effects on both trabecular and cortical bone. ACE-011 increased bone mineral density, improved bone architecture, increased the mineral apposition and bone formation rates and improved bone mechanical strength. These effects have been demonstrated in therapeutic models of bone loss in which ACE-011 has stimulated bone formation – a significant unmet medical need that is underserved by current treatments for bone loss.

About Acceleron Pharma

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 two protein families: the Growth and Differentiation Factors (GDFs) and Bone Morphogenetic Proteins (BMPs). ACE-011, an anabolic bone agent, is the company’s lead program, and is being developed to reverse bone loss in diseases such as cancer-related bone loss and osteoporosis. In addition, the company is advancing through preclinical development with 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, Flagship Ventures, OrbiMed Advisors, Polaris Ventures, Sutter Hill Ventures and Venrock.

Contact: Steven Ertel, Vice President, Corporate Development, Acceleron Pharma, tel: 617-520-1334 and Paul Kidwell (Media) Suda Communications, tel: 617-296-3854.

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