On May 8, 2017 Acceleron Pharma Inc. (NASDAQ:XLRN) and Celgene Corporation (NASDAQ:CELG), reported preliminary Phase 2 results from the ongoing three-month base and long-term extension studies with investigational drug luspatercept in patients with lower-risk myelodysplastic syndromes (MDS) at the 14th International Symposium on MDS in Valencia, Spain (Press release, Celgene, MAY 6, 2017, View Source [SID1234518896]). Luspatercept is being developed as part of the global collaboration between Acceleron and Celgene.

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"These positive data presented in lower-risk MDS confirm our optimism in new opportunities for luspatercept beyond our ongoing Phase 3 trials," said Michael Pehl, President, Hematology and Oncology for Celgene. "We are now planning a Phase 3 clinical trial to expand the development of luspatercept into this lower-risk MDS patient population."

"There is a high unmet medical need for a drug to treat patients earlier in the MDS treatment paradigm," said Habib Dable, President and CEO of Acceleron. "We continue to be motivated to find additional opportunities for luspatercept to treat anemia due to rare blood disorders and remain on track to initiate Phase 2 trials in myelofibrosis and non-transfusion dependent beta-thalassemia by year-end."

Luspatercept Phase 2 Data in First-Line, Lower-Risk MDS Patients

In lower-risk, erythropoiesis-stimulating agent (ESA)-naïve MDS patients, 48% (11/23) of patients treated with luspatercept achieved red blood cell transfusion independence (RBC-TI) and 51% (20/39) of patients achieved a clinically meaningful erythroid hematological improvement (HI-E) response per the International Working Group’s (IWG) criteria. The response rates were positive in patients treated with luspatercept in both ESA-naïve and prior ESA-treated patients.

IWG HI-E, N=82
n (%)

RBC-TI, N=56
n (%)
ESA-Naïve 20/39 (51%) 11/23 (48%)
Prior ESA 22/43 (51%) 11/33 (33%)

Luspatercept Phase 2 Data in RS+ and RS- Lower-Risk MDS Patients

In patients with baseline erythropoietin (EPO) levels ≤ 500 international units per liter (IU/L), RBC-TI and IWG HI-E response rates were positive in both ring sideroblast-positive (RS+) and -negative (RS-) patients.

Baseline
EPO (IU/L)
RS Status
IWG HI-E, N=82
n (%)

RBC-TI, N=56
n (%)
≤ 500 RS+ 30/46 (65%) 16/29 (55%)
RS- 6/14 (43%) 4/7 (57%)
> 500 RS+ 5/9 (56%) 2/9 (22%)
RS- 1/11 (9%) 0/9 (0%)
Unknown 0/2 (0%) 0/2 (0%)
*Table includes both ESA refractory and ESA naïve patients. Patients treated at dose levels ≥ 0.75 mg/kg.

Luspatercept Phase 2 Safety Data

The majority of adverse events (AEs) were grade 1 or 2. AEs at least possibly related to study drug that occurred in at least 3 patients during the studies were fatigue, headache, hypertension, diarrhea, arthralgia, bone pain, injection site erythema, myalgia, and edema peripheral. Grade 3 non-serious AEs possibly or probably related to study drug were ascites, blast cell count increase, blood bilirubin increase, hypertension, platelet count increase, and pleural effusion. Grade 3 serious AEs possibly or probably related to study drug were general physical health deterioration and myalgia.

Luspatercept is an investigational product that is not approved for use in any country.

The oral presentation given at the 14th International Symposium on MDS is available on Acceleron’s website (www.acceleronpharma.com) under the Science tab.

Acceleron MDS Symposium Conference Call Information

Acceleron will host a conference call and live webcast to discuss data presented at the MDS Symposium and its first quarter operational and financial results on May 8, 2017, at 8:00 a.m. EDT. To participate by teleconference, please dial 877-312-5848 (domestic) or 253-237-1155 (international) and refer to the Acceleron Earnings Call.

To access the live webcast, please select "Events & Presentations" in the Investors/Media section on Acceleron’s website (www.acceleronpharma.com) at least 10 minutes beforehand to ensure time for any downloads that may be required.

An archived webcast recording will be available on the Acceleron website beginning approximately two hours after the event.

About the MDS Phase 2 Studies

Data from two Phase 2 studies were presented at the conference: the base study in which patients received treatment with luspatercept for three months and the long-term extension study in which patients may receive treatment with luspatercept for up to an additional five years. In both the three-month base study and the long-term extension study, lower-risk MDS patients were enrolled and treated with open-label luspatercept, dosed subcutaneously once every three weeks.

The outcome measures for the studies included the proportion of patients who had an erythroid response (IWG HI-E) or achieved RBC transfusion independence (RBC-TI). IWG HI-E was defined as hemoglobin increase ≥ 1.5 g/dL sustained for ≥ 8 weeks in patients with < 4 units RBC / 8 weeks transfusion burden at baseline and hemoglobin levels below 10 g/dL. For patients with a ≥ 4 units RBC / 8 weeks transfusion burden at baseline, erythroid response was defined as a reduction of ≥ 4 units RBC sustained for ≥ 8 weeks. RBC-TI was defined as no RBC transfusions for ≥ 8 weeks in patients with a ≥ 2 units RBC / 8 weeks baseline transfusion burden.

About Luspatercept

Luspatercept is a modified activin receptor type IIB fusion protein that acts as a ligand trap for members in the transforming growth factor-beta superfamily involved in the late stages of erythropoiesis (red blood cell production). Luspatercept regulates late-stage erythrocyte (red blood cell) precursor cell differentiation and maturation. This mechanism of action is distinct from that of erythropoietin (EPO), which stimulates the proliferation of early-stage erythrocyte precursor cells. Acceleron and Celgene are jointly developing luspatercept as part of a global collaboration. Acceleron and Celgene are enrolling Phase 3 clinical trials that are designed to evaluate the safety and efficacy of luspatercept in patients with myelodysplastic syndromes (the "MEDALIST" study) and in patients with beta-thalassemia (the "BELIEVE" study). For more information, please visit www.clinicaltrials.gov.