Phase 2 Study of Patients with Multiple Myeloma

Celgene Corporation and Acceleron Pharma Initiate Phase 2 Study of ACE-011 in Patients with Multiple Myeloma

CAMBRIDGE, Mass. – October 16, 2008 – Celgene Corporation (NASDAQ:CELG) and Acceleron Pharma, Inc., a biopharmaceutical company developing novel therapeutics that modulate the growth of tissues including bone and muscle, today announced the initiation of a Phase 2 clinical study of its lead compound ACE-011 in patients with multiple myeloma. ACE-011 is being developed to treat bone loss associated with multiple myeloma and other cancers. The clinical study is designed to assess the safety and efficacy of ACE-011 in multiple myeloma patients with osteolytic bone lesions. Celgene Corporation will make a $5 million milestone payment to Acceleron in accordance with the terms of the collaboration agreement between the two companies.


“We are excited to begin the first ACE-011 Phase 2 study in multiple myeloma patients suffering from cancer-related bone loss,” said Matthew Sherman, M.D., Chief Medical Officer of Acceleron. “We have encouraging results from Phase 1 studies with ACE-011, and believe that it holds promise as a novel bone-forming agent to treat the serious and debilitating effects of bone loss resulting from progression of tumors in myeloma or other cancers. Acceleron plans to present results from the Phase 1 studies at scientific and medical conferences later this year.”

The Phase 2, multi-center, randomized, double-blind, placebo-controlled study is designed to assess the safety and efficacy of multiple doses of ACE-011 in multiple myeloma patients with osteolytic bone lesions. The study will be a multi-center trial conducted in Russia and patients will be treated with standardized anti-myeloma therapy consisting of melphalan, prednisone and thalidomide and randomized to receive either monthly doses of ACE-011 or placebo for up to three months. This study is funded in part by a grant from the Multiple Myeloma Research Foundation.

About ACE-011

ACE-011, a soluble form of the activin receptor type IIA (ActRIIA), is a biologic therapeutic that inhibits signaling through the ActRIIA receptor. By blocking signaling though ActRIIA, ACE-011 stimulates bone formation. In numerous animal models of diseases involving bone loss, ACE-011 significantly increased bone mineral density, improved bone architecture, increased bone formation rate and bone mechanical strength. In Phase 1 clinical studies in healthy volunteers, ACE-011 had an encouraging safety profile, increased biomarkers of bone formation and increased bone mineral density. ACE-011 is being jointly developed by Acceleron and Celgene Corporation for the treatment of cancer-related bone loss.

About Multiple Myeloma and Metastatic Bone Disease

Multiple myeloma is a cancer of the blood in which malignant plasma cells are overproduced in the bone marrow. When functioning normally, plasma cells are part of the immune system that helps fight infection and disease. In multiple myeloma, the malignant plasma cells form tumors that affect the function of the bone marrow and cause damage to the surrounding bone. This bone damage leads to severe bone pain and fractures of the bone which are disabling and often require surgery or radiation therapy.

Metastatic bone disease is a serious complication that develops when solid tumors metastasize, or spread, from the originally affected organ to bone. These tumors secrete factors in the bone allowing tumor proliferation and causing debilitating bone lesions. Many patients with breast or lung cancer will have tumors that metastasize to the bone and these patients will suffer from severe bone pain and fractures.

About Celgene/Acceleron Collaboration

On February 20, 2008, under the terms of the agreement, Celgene and Acceleron announced that they will jointly develop, manufacture and commercialize Acceleron’s products for bone loss. Celgene made an upfront payment to Acceleron of $50 million, which included a $5 million equity investment in Acceleron. In addition, in the event of an initial public offering of Acceleron, Celgene will purchase a minimum of $7 million of Acceleron common stock.

Acceleron is responsible for initial activities including research and development through the end of Phase 2a clinical trials as well as manufacturing the clinical supplies for these studies. In turn, Celgene will conduct the Phase 2b and Phase 3 clinical studies and will oversee the manufacture of Phase 3 and commercial supplies. Acceleron will pay a share of the development expenses and is eligible to receive development, regulatory and commercial milestones of up to $510 million for the ACE-011 program and up to an additional $437 million for each of the three discovery stage programs. Both companies will co-promote the products in North America. Acceleron will receive tiered royalties on worldwide net sales.

About Celgene

Celgene Corporation, based in Summit, New Jersey, is an integrated global biopharmaceutical company engaged primarily in the discovery, development and commercialization of novel therapies for the treatment of cancer and inflammatory diseases through gene and protein regulation. For more information, please visit the Company's website at www.celgene.com.

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 Paul Kidwell (Media)

Vice President, Corporate Development Suda Communications LLC, tel: 617-296-3854

Celgene Corporation:

Greg Geissman, 908-673-9854

Associate Director, Public Relations