ACE-011 Improves Multiple Myeloma Bone Disease in a Preclinical Model

Novel Approach Represents a Significant Advance for the Treatment of Cancer-related Bone Loss

Kos, Greece – June 26, 2007 - Acceleron Pharma, Inc., a biopharmaceutical company developing therapeutics for the treatment of musculoskeletal, metabolic and cancer-related diseases, today announced results demonstrating that ACE-011, a novel anabolic bone agent for the treatment of bone loss, preserved bone mass and architecture in a murine model of multiple myeloma. Multiple myeloma is a malignancy of plasma cells in the bone marrow that disrupts normal bone marrow function resulting in fractures, vertebral compressions and bone pain. The data were presented today at the 11th International Myeloma Workshop in Kos, Greece.

“The positive results from this study support the growing body of evidence that ACE-011 is a novel bone anabolic agent and may be the first anabolic agent for the treatment of cancer-related bone loss in diseases such as multiple myeloma”, said Jasbir Seehra, Ph.D., Chief Scientific Officer at Acceleron.

In the study conducted by Professor Peter Croucher, Ph.D. at the University of Sheffield (UK), mice treated with ACE-011 maintained their bone mass, while untreated mice developed substantial bone loss as a result of the myeloma. Histomorphometry analysis revealed that mice treated with ACE-011 had normal bone formation parameters, while untreated mice had reduced bone formation and increased bone resorption. Furthermore, ACE-011 preserved the number of osteoblasts, the cells responsible for forming new bone, compared to untreated mice which lost these vital bone-forming cells.

“Anti-resorptive agents are current standard of care for multiple myeloma patients yet significant unmet medical need remains as patients continue to experience serious clinical complications such as bone pain and fractures”, said Matthew L. Sherman, M.D., Chief Medical Officer at Acceleron. “We are excited by the encouraging results in this preclinical model of multiple myeloma as we prepare for a phase 2 clinical trial in multiple myeloma later this year”.

Acceleron is developing therapeutics that addresses the clinical consequences of cancer, such as bone loss and/or muscle loss, as well as treatments that directly target the underlying tumor. Given the improving therapeutic outcomes leading to more cancer patients living longer with their disease, the frequency of secondary consequences of cancer is increasing.

About ACE-011

ACE-011, a novel bone anabolic agent currently in a phase 1 clinical trial, is a protein therapeutic based on the activin receptor IIA. 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 Multiple Myeloma

Multiple myeloma is a malignancy of plasma cells in the bone marrow that disrupts normal bone marrow function. Myeloma cells invade and destroy the bone surrounding the marrow cavity leading to rapid and widespread osteoporosis and osteolytic bone lesions, resulting in fractures, vertebral compressions and bone pain. Intravenous bisphosphonates are the current standard of care, but significant unmet medical need remains since most patients will still have serious bone complications despite treatment. According to the International Myeloma Foundation, there are an estimated 750,000 people worldwide multiple myeloma. In the US and EU, there are approximately 80,000 myeloma patients whose disease has affected their bones.

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 on 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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