Acceleron to Present Dalantercept Clinical Data at the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting

Acceleron Pharma Inc. (NASDAQ:XLRN), a clinical stage biopharmaceutical company focused on the discovery, development and commercialization of novel therapeutic candidates that regulate cellular growth and repair, today announced that data from the DART study, an ongoing phase 2 clinical trial of dalantercept in patients with advanced renal cell carcinoma (RCC) will be presented at the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting in Chicago, IL.

Details for the two poster presentations are provided below:

The posters will be available on Acceleron’s website (www.acceleronpharma.com) under the Publications section on June 1, 2015.

About the DART Phase 2 Clinical Trial in RCC

The Phase 2 DART clinical trial is a two-part study in patients with advanced renal cell carcinoma. Part 1 is a dose-escalation study of dalantercept in combination with axitinib to evaluate the safety and tolerability of the combination in patients whose disease has progressed following one to three lines of prior therapy. Part 2 is a randomized, double-blind study of 130 patients with advanced renal cell carcinoma who have progressed following treatment with a VEGF receptor tyrosine kinase inhibitor. Patients may have also received prior mTOR therapy and/or immunotherapy. The objective of the study is to determine whether treatment with dalantercept in combination with axitinib prolongs progression-free survival compared to treatment with placebo plus axitinib. For additional information on this clinical trial, please visit www.clinicaltrials.gov, identifier NCT01727336.

About Dalantercept

Dalantercept (ACE-041) is an investigational protein therapeutic that inhibits angiogenesis by preventing BMP9, a protein in the Transforming Growth Factor-Beta (TGF-beta) superfamily, from interacting with activin receptor-like kinase 1 (ALK1), a cell-surface receptor found on proliferating vascular endothelial cells. Dalantercept inhibits ALK1 signaling, which is required for the development of mature, functional vasculature.

About Acceleron

Acceleron is a clinical stage biopharmaceutical company focused on the discovery, development and commercialization of novel therapeutic candidates that regulate cellular growth and repair. The company is a leader in understanding the biology of the TGF-beta protein superfamily, a large and diverse group of molecules that are key regulators in the growth and repair of tissues throughout the human body, and in targeting these pathways to develop important new medicines. Acceleron has built a highly productive R&D platform that has generated innovative clinical and preclinical therapeutic candidates with novel mechanisms of action. These therapeutic candidates have the potential to significantly improve clinical outcomes for patients with cancer and rare diseases.

For more information, please visit www.acceleronpharma.com.