Acceleron Announces Updated Results from Ongoing Phase 2 Trials of Luspatercept in Myelodysplastic Syndromes at the 59th Annual Meeting of the American Society of Hematology

Acceleron Pharma Inc. (NASDAQ:XLRN), a leading biopharmaceutical company in the discovery and development of TGF-beta therapeutics to treat serious and rare diseases, today announced preliminary results from the ongoing Phase 2 trials with luspatercept in patients with lower-risk myelodysplastic syndromes (MDS) at the 59^th Annual Meeting of the American Society of Hematology (ASH) in Atlanta, Georgia. Luspatercept is being developed as part of a global collaboration between Acceleron and Celgene.

“As the Phase 2 results in MDS mature, we are excited to see luspatercept achieving a clinically meaningful erythroid response in over 50% of patients. Luspatercept continues to provide long-term benefit to multiple patients now nearing three years on treatment. These results further reinforce luspatercept’s potential to be a transformative treatment option for patients living with lower-risk MDS,” said Habib Dable, President and Chief Executive Officer of Acceleron. “We look forward to the upcoming MEDALIST and BELIEVE Phase 3 trial top-line data readouts in mid-2018, and we and Celgene continue to make considerable progress toward initiating the COMMANDS Phase 3 trial during the first half of 2018.”

Phase 2 Results

A total of 99 lower-risk MDS patients have been treated with therapeutic dose levels of luspatercept (≥ 0.75 mg/kg) in the ongoing Phase 2 trials.

• 53% (52 of 99 patients) achieved a clinically meaningful erythroid response of an increase in hemoglobin or reduction in red blood cell (RBC) transfusion burden as per the International Working Group’s Hematologic Improvement Erythroid (IWG HI-E) response criteria.
• 43% (29 of 67 patients) with an RBC transfusion burden at baseline of ≥ 2 units per 8 weeks achieved RBC transfusion independence (RBC-TI) for ≥ 8 weeks.
  • In an updated analysis of the 23 RBC-TI responders previously reported at EHA 2017, the median duration of treatment increased to 19.0 months from 14.7 months. The current duration of treatment for RBC-TI responders ranges from 2.8 months to 37.3 months.
• Patients with a low transfusion burden at baseline (< 4 RBC units per 8 weeks and hemoglobin < 10 g/dL) demonstrated a clinically meaningful increase in hemoglobin for up to 34 months, with multiple ongoing.

The results presented at ASH 2017 confirm and extend previously reported results across the lower-risk MDS patient subpopulations, showing erythroid responses regardless of prior use of erythropoiesis-stimulating agents (ESA), baseline erythropoietin (EPO) levels, and ring sideroblast (RS) status.