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Acceleron Pharma Presents Anabolic Bone Effects of ACE-661 at International Scientific Meeting

Novel BMP signaling inhibitor expands understanding of bone biology and has therapeutic potential for bone loss

CAMBRIDGE, Mass.--(BUSINESS WIRE)--May 9, 2011 - Acceleron Pharma, Inc., a biopharmaceutical company developing protein therapeutics for cancer and orphan diseases, presented preclinical data highlighting the significant anabolic bone effects in normal and osteopenic mice of RAP-661. Treatment with the investigational compound showed increased bone mineral density, increased osteoblast activity and decreased osteoclast activity. Aaron Mulivor, Ph.D. from Acceleron presented these data at the 3rd Joint Meeting of the European Calcified Tissue Society & the International Bone and Mineral Society in Athens, Greece, 7-11 May 2011.

The bone morphogenetic protein receptor type 1A (BMPR1A) is a high-affinity receptor for members of the BMP family, which contribute to the development and remodeling of bone. ACE-661 is a soluble fusion protein consisting of the extracellular domain of human BMPR1A and the Fc portion of human IgG1. RAP-661 is a murine version of ACE-661. In this study, mice underwent an ovariectomy (OVX) and were aged to establish bone loss. A control group underwent sham surgery and did not develop bone loss. The OVX and sham surgery mice were each separated into treatment groups to receive one of the following: twice weekly injections of RAP-661, the bone anabolic agent parathyroid hormone (PTH), the antiresorptive agent zoledronate, or placebo.

Summary of results:


  • After six weeks of treatment, RAP-661 significantly increased trabecular bone (tibia) volume and cortical bone (femur) thickness compared to placebo in both OVX and sham-treated mice.
  • Whole-body bone mineral density (BMD) as measured by DEXA after six weeks' treatment in OVX mice revealed that RAP-661 increased BMD from baseline by 14%, compared with increases of 14% for PTH, 7% for zoledronate, and 2% for placebo. In sham-treated mice with no bone loss, RAP-661 increased whole-body BMD by 12%, compared with increases of 9% for PTH, 8% for zoledronate and 1% for placebo.
  • Bone mechanical strength was significantly increased in RAP-661 treated OVX mice.
  • Histomorphometry and serum biomarker analysis showed an increase in osteoblast activity and a reduction in osteoclast activity, suggesting that RAP-661 has both anabolic and anti-resorptive effects.

“Over the past two decades, scientists and clinicians have recognized the important roles that BMPs play in the development and remodeling of bone,” said Ravindra Kumar, PhD, Vice President of Cell Biology at Acceleron Pharma. “The rapid and significant increases in bone mass, volume and strength we observed with systemic administration of RAP-661 are remarkable. These results expand our understanding of bone biology and support the therapeutic potential for ACE-661 in patients with bone loss.”

About ACE-661

ACE-661, a novel bone anabolic agent currently in preclinical research, is a protein therapeutic based on the bone morphogenetic protein receptor type 1A (BMPR1A). In normal rodents and in preclinical models of bone loss, a murine form of ACE-661 increased bone mineral density, increased osteoblast activity and decreased osteoclast activity.

About Bone Loss

Bone loss poses significant clinical concerns for patients and economic challenges to society. Causes of bone loss include diseases (notably osteoporosis and advanced cancers that spread to bones, such as lung and multiple myeloma), treatment with certain medications (hormone therapy for prostate or breast cancer and corticosteroids for various diseases); and trauma relating to fractures. There is tremendous need for a novel therapy that not only halts bone degradation but also can rebuild bone, even after substantial loss has already occurred.

About Acceleron Pharma

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


Contact: Acceleron Pharma:
Steven Ertel, 617-649-9234
Senior Vice President, Corporate Development
Suda Communications LLC
Maureen L. Suda, 585-387-9248


Posted: May 2011