Acceleron Pharma Initiates First-in-Human Study of ACE-041, a Novel Angiogenesis Inhibitor, in Patients with Advanced Cancer.

Company advances 3rd internally discovered program into clinical studies

CAMBRIDGE, Mass. -- Acceleron Pharma, Inc., a biopharmaceutical company developing novel therapeutics that modulate the growth of cells and tissues including red blood cells, bone, muscle, fat, and the vasculature, today announced the initiation of a Phase 1 clinical study of ACE-041, a novel angiogenesis inhibitor that binds to and prevents members of the TGF- superfamily from signaling through the activin receptor-like kinase 1 (ALK1) receptor. The Phase 1 trial is a multiple-dose, dose-escalating study designed to assess the safety, tolerability, pharmacokinetics, and preliminary anti-tumor activity of ACE-041 in patients with advanced cancer.

"There is a tremendous need for novel angiogenesis inhibitors in cancer. The first generation treatments, while ground-breaking, ultimately showed that VEGF is just one piece of the tumor angiogenesis puzzle," said Matthew Sherman, M.D., Chief Medical Officer at Acceleron. "ACE-041, with its unique mechanism of action of targeting members of the TGF- superfamily of proteins by using the ALK1 receptor, has the potential to become an important addition to anti-angiogenesis therapy."

"We are pleased to advance ACE-041 into human clinic studies, as it underscores the richness and versatility of our discovery platform," said John Knopf, Ph.D., Chief Executive Officer of Acceleron. "In the past few months, we have initiated three clinical studies of three separate programs, with the potential to treat anemia, bone loss, neuromuscular disease, and cancer. We are proud of how rapidly the Acceleron pipeline is maturing and expanding. These unique therapies may one day offer new hope to patients who desperately need novel treatments for serious and life-threatening diseases."

ACE-041 is a novel angiogenesis inhibitor that binds to and prevents members of the TGF- superfamily from signaling through the activin receptor-like kinase 1 (ALK1) receptor. Unlike current treatments, ACE-041 prevents angiogenesis by blocking a common, later phase of the blood vessel development process termed vascular maturation. In preclinical studies, ACE-041 inhibits blood vessel formation induced by multiple angiogenesis factors, including VEGF and FGF, even though ACE-041 does not bind to these molecules. In several animal models of cancer, administration of ACE-041 inhibits tumor growth and prolongs survival by preventing tumor-induced angiogenesis.

Acceleron's commitment to being the leader in the field of developing therapeutics based on inhibiting members of the TGF- superfamily was further strengthened by the recent issuance of a patent covering antibodies to ALK1. In addition to other patents covering the use of a soluble ALK1 receptor to inhibit angiogenesis, Acceleron has established a strong and broad portfolio of intellectual property covering therapeutics targeting the ALK1 pathway.

About Acceleron

Acceleron is a privately held biopharmaceutical company committed to discover, develop, manufacture and commercialize novel biotherapeutics that modulate the growth of red blood cells, 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 TGF- superfamily of proteins. ACE-011 is currently being studied in two Phase 2 clinical trials in cancer patients. ACE-031 is currently being studied in a Phase 1 clinical trial in healthy volunteers. In addition, the company is advancing new product candidates that increase muscle mass, control angiogenesis, inhibit fat accumulation and increase hemoglobin. 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 include Advanced Technology Ventures, Bessemer Ventures, Celgene, Flagship Ventures, MPM BioEquities, OrbiMed Advisors, Polaris Ventures, QVT Financial, Sutter Hill Ventures and Venrock. For more information, visit www.acceleronpharma.com.