“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

“We are excited to see the initiation of this late-stage clinical trial of sotatercept as there is enormous unmet medical need for a safe and effective alternative to ESAs for the treatment for chemotherapy-induced anemia,” said Matthew Sherman, MD, Chief Medical Officer of Acceleron. “This study, along with an ongoing Phase 2 clinical trial in patients with end-stage renal disease on hemodialysis, will provide insight into the therapeutic potential of sotatercept as a first-in-class treatment for anemia.”

The clinical trial is designed as a randomized, dose ranging study of sotatercept in patients with metastatic cancer followed by a double-blind, randomized, placebo-controlled study of sotatercept for chemotherapy-induced anemia (CIA) in patients with metastatic non-small cell lung cancer (NSCLC) treated with first-line platinum-based chemotherapeutic regimens. For additional information on the clinical trial, please visit clinicaltrials.gov and query NCT01284348.

About Chemotherapy-Induced Anemia (CIA)

Anemia is one of the most common and debilitating complications associated with cancer chemotherapy, which depletes and prevents formation of red blood cells, leading to fatigue and weakness. Recent studies of erythropoietin-stimulating agents (ESAs) have shown an increased risk of mortality arising from exposure to high levels of recombinant erythropoietin and its derivatives, which may stimulate tumor progression and increase the occurrence of thromboembolic events. Currently, blood transfusions are the only effective alternative treatment for anemia, and are associated with the risk of transmissible diseases. There is a significant unmet need for safe and effective alternatives to ESAs and transfusions for the management of CIA.

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 expected 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 Pharma, please visit www.acceleronpharma.com.

About Acceleron/Celgene Collaboration

Under the terms of the agreement, Celgene and Acceleron will jointly develop, manufacture and commercialize sotatercept. Acceleron will retain responsibility 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 sotatercept program and up to an additional $437 million for each of three discovery stage programs. The companies will co-promote the products in North America. Acceleron will receive tiered royalties on worldwide net sales.

CONTACT:

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

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

Celgene Corporation:
Greg Geissman, 908-673-9854
Associate Director, Public Relations