Cambridge, Mass. – April 3, 2012 – Acceleron Pharma, Inc., a biopharmaceutical company developing protein therapeutics for cancer and orphan diseases, announced that collaborators at Beth Israel Deaconess Medical Center presented preclinical data today at the American Association for Cancer Research (AACR) Annual Meeting 2012 which showed that ACE-041, an activin-receptor like kinase 1 (ALK1) receptor ligand trap, when used in combination with sunitinib, inhibited tumor growth in a model of VEGF-inhibitor-resistant renal cell carcinoma (RCC).

Anti-angiogenesis therapies, including the VEGF-inhibitor sunitinib, are currently the standard of care in metastatic RCC.  While these treatments cause tumor shrinkage and extend progression-free survival in many patients, the responses are typically short-lived due to the development of drug resistance. Mice bearing A498 and 786-0 human RCC xenografts that receive anti-VEGF treatment mirror this clinical experience with a period of tumor stabilization that is followed by the restoration of angiogenesis and resumption of growth despite continued drug administration.  The preclinical data, presented by Rupal Bhatt, M.D., Ph.D., Assistant Professor, Hematology-Oncology, Beth Israel Deaconess Medical Center provide evidence that combining two distinct anti-angiogenic drugs, a VEGF inhibitor and ACE-041, may produce an enhanced therapeutic effect in the treatment of metastatic RCC.

Preclinical Study Description and Results

Two renal cell carcinoma cell lines (A498 and 786-O) were used in a mouse xenograft model.  In each tumor cell line, mice treated with the combination of ACE-041 and sunitinib slowed tumor growth to a greater extent than either agent alone.  Additionally, the combination of ACE-041 and sunitinib prevented the restoration of tumor perfusion during the resistant phase of sunitinib-alone treatment and lowers tumor perfusion to a greater extent than sunitinib-alone.

“These data demonstrate that blocking ALK1 ligand signaling, either alone or in combination with other anti-angiogenesis therapies, may be an attractive strategy for treatment of renal cell carcinoma,” said Dr. Bhatt.

“There is increasing evidence that combining anti-angiogenesis inhibitors with distinct mechanisms of action, such as a VEGF inhibitor with an ALK1 ligand trap, like ACE-041, can more effectively inhibit tumor angiogenesis,” said Matthew Sherman, M.D., Chief Medical Officer at Acceleron.  “We believe this approach holds great promise and we’re excited to pursue Phase 2 studies of ACE-041 in combination with VEGF inhibitors later this year.”

About ACE-041

ACE-041 is an ALK1 ligand trap that inhibits angiogenesis by preventing BMP9 and BMP10, members of the TGFβ protein superfamily, from interacting with activin receptor-like kinase 1 (ALK1), a receptor found on proliferating endothelial cells. ACE-041 inhibits ALK1 signaling, which is required for the development of mature, functional capillary networks. In animal studies, treatment with ACE-041 inhibits tumor angiogenesis and growth.  In a clinical study of patients with advanced, refractory solid tumors, treatment with ACE-041 was generally well-tolerated and antitumor activity was observed, resulting in tumor shrinkage and stabilization of disease. ACE-041 is being studied in a Phase 2 clinical trial in patients with squamous cell carcinoma of the head and neck.

About Acceleron

Acceleron is a privately-held biopharmaceutical company committed to discover, develop, manufacture and commercialize novel protein therapeutics for orphan diseases and cancer. Acceleron’s scientific approach takes advantage of its unique insight to discover first-in-class therapies based on the TGF-β protein superfamily. Acceleron utilizes proven biotherapeutic technologies and capitalizes on the company’s internal GMP manufacturing capability to advance its therapeutic programs rapidly and efficiently. The investors in Acceleron include Advanced Technology Ventures, Alkermes, Avalon Ventures, Bessemer Ventures, Celgene, Flagship Ventures, MPM BioEquities, OrbiMed Advisors, Polaris Ventures, QVT Financial, Sutter Hill Ventures and Venrock. For further information on Acceleron, please visit www.acceleronpharma.com.

CONTACT:

Acceleron Pharma:
Steven Ertel, 617-649-9234
Chief Business Officer

Maureen L. Suda (Media)
Suda Communications LLC
585-387-9248

###

“This fortifies Acceleron’s solid financial position and provides the Company with the resources to continue to advance and expand our robust clinical and preclinical pipeline”, said John Knopf, Ph.D., Chief Executive Officer of Acceleron.  “We’re especially pleased with Celgene’s commitment to Acceleron as we jointly develop several promising products for the treatment of anemia.”

In conjunction with this financing, George Golumbeski, Senior Vice President of Corporate Development of Celgene, has joined the Acceleron Board of Directors.

About Acceleron

Acceleron is a privately-held biopharmaceutical company committed to discover, develop, manufacture and commercialize novel protein therapeutics for orphan diseases and cancer. Acceleron’s scientific approach takes advantage of its unique insight to discover first-in-class therapies based on the TGF-β protein superfamily. Acceleron utilizes proven biotherapeutic technologies and capitalizes on the company’s internal GMP manufacturing capability to advance its therapeutic programs rapidly and efficiently. The investors in Acceleron include Advanced Technology Ventures, Alkermes, Avalon Ventures, Bessemer Ventures, Celgene, Flagship Ventures, MPM BioEquities, OrbiMed Advisors, Polaris Ventures, QVT Financial, Sutter Hill Ventures and Venrock. For further information on Acceleron, please visit www.acceleronpharma.com.

Contact:

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

Maureen L. Suda (Media)
Suda Communications LLC, 585-387-9248

# # #

Piper Jaffray 23^rd Annual Health Care Conference

Date:                Wednesday, November 30, 2011

Location:          The New York Palace, New York City

Time:                9:30 to 9:50 AM (EST)

Oppenheimer 22^nd Annual Healthcare Conference
Date:                Tuesday, December 13, 2011

Location:          The Waldorf-Astoria, New York City

Time:                9:40 to 9:55 AM (EST)

About Acceleron

Acceleron is a privately-held biopharmaceutical company committed to discover, develop, manufacture and commercialize novel protein therapeutics for orphan diseases and cancer. Acceleron’s scientific approach takes advantage of its unique insight to discover first-in-class therapies based on the TGF-β protein superfamily. Acceleron utilizes proven biotherapeutic technologies and capitalizes on the company’s internal GMP manufacturing capability to advance its therapeutic programs rapidly and efficiently. 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 further information on Acceleron, please visit www.acceleronpharma.com.

CONTACT:

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

Maureen L. Suda (Media)
Suda Communications LLC, 585-387-9248

# # #

CAMBRIDGE, Mass. – September 13, 2011 –  Acceleron Pharma, Inc., a biopharmaceutical company developing protein therapeutics for cancer and orphan diseases today announced that it has initiated a Phase 1 clinical study of ACE-536.  ACE-536 is a ligand trap that increases red blood cells and hemoglobin by inhibiting members of the TGF-beta superfamily involved in late stages of erythropoiesis.  ACE-536 is being developed for the treatment of anemia in a global collaboration with Celgene Corporation. The Phase 1 clinical trial is a multiple-dose, dose-escalating study designed to assess the safety, tolerability, pharmacokinetics and pharmacodynamics of ACE-536.  Acceleron will receive a $7.5 million payment from Celgene for achieving this milestone event.

“ACE-536 has the potential to make a significant impact on the treatment of anemia, specifically, in diseases such as Myelodysplastic syndromes and beta-thalassemia in which the severe anemia isn’t well managed by currently available therapies.  By affecting production of red blood cells via a mechanism distinct from erythropoiesis stimulating agents, ACE-536 may become an option for patients for whom current therapies are ineffective,” said John Knopf, Ph.D., Chief Executive Officer of Acceleron. “Acceleron’s leadership in the biology of the TGF-beta superfamily proteins and our related expertise in discovering, developing and manufacturing potent biologic modulators of these proteins has enabled incredible productivity achievements in a short period of time.  ACE-536 is our fourth internally discovered, developed and manufactured drug to enter human clinical trials in the past five years.”

About ACE-536

ACE-536 is a ligand trap that increases red blood cells and hemoglobin by inhibiting members of the TGF-beta superfamily involved in the late stages of erythropoiesis.  ACE-536 affects the red blood cell production by a distinct mechanism from currently available erythropoiesis stimulating agents and has the potential to treat anemia in diseases such as Myelodysplastic syndromes (MDS) and beta-thalassemia that are poorly managed with current therapy.  In MDS, a subset of patients has a defect in the late stage maturation process of red blood cell precursors.  ACE-536 specifically targets and positively affects late stage red blood cell maturation and therefore ACE-536 may be particularly effective in correcting the anemia in these MDS patients.

About Acceleron

Acceleron is a privately-held biopharmaceutical company committed to discover, develop, manufacture and commercialize novel protein therapeutics for orphan diseases and cancer. Acceleron’s scientific approach takes advantage of its unique insight to discover first-in-class therapies based on the TGF-β protein superfamily. Acceleron utilizes proven biotherapeutic technologies and capitalizes on the company’s internal GMP manufacturing capability to advance its therapeutic programs rapidly and efficiently. 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 further information on Acceleron, please visit www.acceleronpharma.com.

CONTACT:

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

Maureen L. Suda (Media)
Suda Communications LLC, 585-387-9248

Rodman & Renshaw Annual Global Investment Conference

Date:                Tuesday, September 13, 2011

Location:           The Waldorf-Astoria, New York City

Time:                3:15 to 3:40 PM (EDT)

2011 UBS Global Life Sciences Conference

Date:                Wednesday, September 21, 2011

Location:           The Grand Hyatt, New York City

Time:                2:00 to 2:30 PM (EDT)

About Acceleron

Acceleron is a privately-held biopharmaceutical company committed to discover, develop, manufacture and commercialize novel protein therapeutics for orphan diseases and cancer. Acceleron’s scientific approach takes advantage of its unique insight to discover first-in-class therapies based on the TGF-β protein superfamily. Acceleron utilizes proven biotherapeutic technologies and capitalizes on the company’s internal GMP manufacturing capability to advance its therapeutic programs rapidly and efficiently. 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 further information on Acceleron, please visit www.acceleronpharma.com.

CONTACT:

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

Maureen L. Suda (Media)
Suda Communications LLC, 585-387-9248

# # #

SUMMIT, NJ and CAMBRIDGE, Mass. – August 3, 2011 –  Acceleron Pharma, Inc., a biopharmaceutical company developing protein therapeutics for cancer and orphan diseases, and Celgene Corporation (NASDAQ: CELG) today announced that the companies have entered into a joint development and commercialization agreement for ACE-536 for the treatment of anemia.  The companies already have a collaboration around sotatercept (ACE-011) entered in 2008.   Under the new agreement, the companies will collaborate to develop both products and potentially others for treating anemia across a wide range of indications.

Celgene and Acceleron will jointly develop, manufacture and commercialize ACE-536, a novel protein therapeutic that inhibits members of the TGF-beta superfamily involved in erythropoiesis, for the treatment of anemia.  Additionally, Celgene will have an option to future Acceleron programs developed for anemia.  Celgene will make an upfront payment to Acceleron of $25 million.

“Acceleron has uncovered an exciting new approach to treating disorders of erythropoiesis, and we are pleased to broaden our successful partnership with Celgene,” said John Knopf, Ph.D., Chief Executive Officer of Acceleron. “Acceleron and Celgene can now combine our strengths to develop molecules to treat a broad array of under-served diseases and conditions in which patients suffer from anemia.  To that end, we look forward to initiating the Phase 1 clinical trial of ACE-536 within the next few months.  ACE-536 is our fourth internally discovered and developed drug to enter the clinic.”

“Celgene and Acceleron have a strong partnership that continues to advance innovative therapies in areas of great unmet medical need,” said Tom Daniel, Ph.D., President, Research, Celgene.  “The work we will embark on with ACE-536 is a natural extension of our strong presence in hematology.  We look forward to exploring the potential of ACE-536 for patients with anemia worldwide.”

Under the terms of the agreement, Acceleron will be responsible for conducting the Phase 1 and initial Phase 2 clinical trials and Celgene will conduct the subsequent Phase 2 and Phase 3 clinical studies.  Acceleron will manufacture ACE-536 for the Phase 1 and Phase 2 clinical trials and Celgene will have responsibility for the manufacture of Phase 3 and commercial supplies.  Acceleron will pay a share of the development expenses through the end of 2012 and Celgene will be responsible for development costs thereafter.  Acceleron is eligible to receive development, regulatory and commercial milestones of up to $217 million for the ACE-536 program.  The companies will co-promote the products in North America.  Acceleron will receive tiered double-digit royalties on worldwide net sales.

About ACE-536

ACE-536 is a ligand trap that inhibits members of the TGF-beta superfamily involved in late stages of erythropoiesis.  ACE-536 and sotatercept are biochemically distinct molecules and may have unique pharmacological attributes that enable their preferential use in particular anemia indications.  In preclinical studies, ACE-536 promotes red blood cell (RBC) formation in the absence of erythropoietin (EPO) signaling, has distinct effects from EPO on RBC differentiation, and acts on a different population of progenitor blood cells than EPO during RBC development.

About ACE-011 / sotatercept

Sotatercept, a soluble receptor fusion protein comprised of extracellular domain of the human activin receptor type IIA (ActRIIA) fused to human immunoglobulin, is a biologic therapeutic.  Blocking signaling through ActRIIA may be a way to increase red blood cell production, promote bone formation, and inhibit tumor growth and metastasis. Sotatercept is the first in a novel class of anemia therapies. In Phase 1 clinical studies in healthy volunteers, sotatercept was generally well tolerated, and increased levels of hemoglobin and hematocrit, biomarkers of bone formation, and bone mineral density. The most common clinically significant adverse events observed included increased hemoglobin and increased hematocrit, which were pharmacologic effects of the drug, and also headache, all of which were manageable and reversible.  Sotatercept is currently being studied in Phase 2 clinical trials in patients with chemotherapy-induced anemia and in patients with end-stage renal disease on hemodialysis.   For more information on ongoing and completed clinical trials of sotatercept, visit clinicaltrials.gov and query “sotatercept.”   Sotatercept is being jointly developed by Acceleron and Celgene Corporation.

About Celgene

Celgene Corporation, headquartered in Summit, New Jersey, is an integrated global pharmaceutical company engaged primarily in the discovery, development and commercialization of innovative 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 protein therapeutics for orphan diseases and cancer. Acceleron’s scientific approach takes advantage of its unique insight to discover first-in-class therapies based on the TGF-β protein superfamily. Acceleron utilizes proven biotherapeutic technologies and capitalizes on the company’s internal GMP manufacturing capability to advance its therapeutic programs rapidly and efficiently. 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 further information on Acceleron, please visit www.acceleronpharma.com.

CONTACT:

Acceleron Pharma:
Steven Ertel, 617-649-9234
SVP, Corporate Development

Celgene Corporation:
Brian Gill, 908-673-9530
VP, Corporate Communications

Maureen L. Suda (Media)
Suda Communications, LLC, 585-387-9248