Acceleron, Celgene Offer Updated Results from Ongoing Phase 2 Study of Luspatercept

Acceleron Pharma Inc. XLRN and Celgene Corporation CELG today announced that preliminary results will be presented from an ongoing long-term Phase 2 extension study in patients with beta-thalassemia during an oral presentation and a separate poster presentation at the 21st Congress of the European Hematology Association (EHA). Results from the presentations showed that 80% (24/30) of patients achieved at least a 20% reduction in transfusion burden and 36% (8/22) of patients achieved a hemoglobin increase of at least 1.5 g/dL in the luspatercept 3-month base study. In the ongoing long-term extension study, 96% (23/24) of patients achieved at least a 20% reduction in transfusion burden and 56% (15/27) of patients achieved a hemoglobin increase of at least 1.5 g/dL. Luspatercept is being developed as part of the global collaboration between Acceleron and Celgene. "The results from the 3-month luspatercept clinical trial were very promising and the data from longer-term treatment are even more encouraging," said Professor Antonio Piga, M.D., Ph.D., Director of Pediatrics at San Luigi Gonzaga University Hospital in Torino, Italy and coordinating principal investigator of the study. "Clinicians and patients are in need of safe and effective therapies for the treatment of beta-thalassemia. These Phase 2 luspatercept data provide strong rationale for the ongoing Phase 3 BELIEVE study of luspatercept in regularly transfused beta-thalassemia patients." Highlights of the Luspatercept Beta-Thalassemia Data Presented at EHA Study Design Data from two Phase 2 studies will be presented at the conference: the completed dose-escalation study in which patients received treatment with luspatercept for three months and the ongoing long-term extension study in which patients receive treatment with luspatercept for up to an additional 24 months. In both the 3-month study and the long-term extension study, red blood cell (RBC) transfusion dependent patients (≥ 4 units RBC / 8 weeks) and non-transfusion dependent patients (< 4 units RBC / 8 weeks) were enrolled and treated with open-label luspatercept, dosed subcutaneously once every 3 weeks. The primary outcome measure of the base study was the proportion of patients who have an erythroid response, defined as 1) a hemoglobin increase of ≥ 1.5 g/dL from baseline for ≥ 14 days (in the absence of RBC transfusions) in non-transfusion dependent patients, or 2) ≥ 20% reduction in RBC transfusion burden compared to pretreatment in transfusion dependent patients. The primary outcome measure of the long-term extension was the safety and tolerability assessed by adverse events. Efficacy Results in Transfusion Dependent (TD) Beta-Thalassemia Patients RBC transfusion reduction over any 12 weeks versus 12 weeks pre-treatment Response rate (% of patients) 3-month base study (n=30) Long-term extension study (n=24) ≥ 20% 80% (24/30) 96% (23/24) ≥ 33% 67% (20/30) 83% (20/24) ≥ 50% 53% (16/30) 67% (16/24) Durability of Response: In the long-term extension study, the duration of the reduction in transfusion burden of ≥ 33% ranged from 12 to 48+ weeks. Results in Non-Transfusion Dependent (NTD) Beta-Thalassemia Patients Hemoglobin (Hb) response over any 12 weeks versus 12 weeks pre-treatment Response rate (% of patients) in patients treated with ≥ 0.6 mg/kg 3-month base study (n=22) Long-term extension study (n=27) Increase in mean Hb ≥ 1.0 g/dL 64% (14/22) 78% (21/27) Increase in mean Hb ≥ 1.5 g/dL 36% (8/22) 56% (15/27) Durability of Response: In the long-term extension study, the duration of hemoglobin increase (≥ 1.0 g/dL) ranged from 113 to 505+ days. Improvement in patient-reported quality of life (QoL) measures in NTD patients: Increases in mean hemoglobin over a 12-week period correlated (r=0.67, p=0.001) with increases in FACIT-F, a patient-reported outcome (PRO) questionnaire used to assess anemia related symptoms Safety Results in TD and NTD Patients TD Patients There were no related serious adverse events and related grade 3 adverse events included: bone pain (n=2 base, n=1 extension), asthenia (n=2 base) and myalgia (n=1 extension) The most common related adverse events (all grades) were bone pain, myalgia, arthralgia, headache, asthenia, and musculoskeletal pain NTD Patients There were no related serious adverse events and one grade 3 related adverse event of headache (n=1) in the extension study The most common related adverse events were bone pain, headache, musculoskeletal pain and arthralgia Luspatercept is an investigational product that is not approved for use in any country. The BELIEVE Trial, a global Phase 3 study in regularly transfused beta-thalassemia patients, is currently enrolling. The slides from the EHA beta-thalassemia presentations will be available immediately following the presentations at the conference on Acceleron's website (www.acceleronpharma.com) under the Science tab.