MEI Pharma Announces Positive Results from Phase II Study of Pracinostat in Acute Myeloid Leukemia, Plans to Initiate Phase III Registration Study

MEI Pharma, Inc.

, an oncology company focused on the clinical development of novel therapies for cancer, today announced positive results from a Phase II study of its investigational drug candidate Pracinostat in combination with azacitidine (marketed as Vidaza®) in elderly patients with newly diagnosed acute myeloid leukemia (AML). The results were presented earlier today at the American Society of Hematology (ASH) Annual Meeting in Orlando. A copy of the presentation is now available at www.meipharma.com. According to the oral presentation by principal investigator Dr. Guillermo Garcia-Manero, MD Anderson Cancer Center, 28 of the 50 patients in the study (56%) achieved the primary endpoint of complete response (CR) plus complete response with incomplete blood count recovery (CRi) plus morphologic leukemia-free state (MLFS), including 21 patients (42%) who achieved a CR. Notably, 19 of the 21 patients who achieved a CR are still alive with a 100% one-year survival rate among all CR patients, indicating a correlation between CR and survival with this low intensity therapy. Median overall survival for all 50 patients in the study has not been reached, with 28 patients still living and a median observation time of 14.3 months. These data compare favorably to a recent international Phase III study of azacitidine (AZA-001)1, which showed a median overall survival of 10.4 months with azacitidine alone and a CR rate of 19.5% in a similar patient population. Median survival among patients with high-risk cytogenetics in this study (n=21) was 13.3 months, more than double the median survival of the high-risk population in the AZA-001 study (6.4 months). "These are impressive results by virtually any measure for a group of patients in dire need of effective new treatment options," said Dr. Garcia-Manero. "Not only did we observe a high rate of responses, but many occurred rapidly and continued to improve with ongoing therapy. Most importantly, we are seeing an encouraging trend in overall survival, particularly among patients who achieved a complete response. These data clearly support further development of Pracinostat in combination with azacitidine for the treatment of elderly patients with AML." The open-label study enrolled a total of 50 patients at 15 centers across the U.S. Median age in the study was 76 years. Patients received 60 mg of Pracinostat orally three times a week for three weeks followed by one week of rest and 75 mg/m2 of azacitidine via subcutaneous injection or intravenous infusion for the first seven days of each 28-day cycle. The combination of Pracinostat and azacitidine was generally well tolerated in the study, with no unexpected toxicities. The most common grade 3/4 treatment-emergent adverse events reported in >10% of all patients included febrile neutropenia, thrombocytopenia, anemia and fatigue. "We are very excited about our growing body of AML data, which continues to exceed expectations and guide us forward with the development of this program," said Daniel P. Gold, Ph.D., President and Chief Executive Officer of MEI Pharma. "Over the past several months we have learned that our randomized study of Pracinostat and azacitidine in myelodysplastic syndrome (MDS) was hindered by a high rate of discontinuations due to adverse events, but appeared to show a benefit for patients who were able to tolerate treatment for at least four cycles compared to azacitidine alone. The results from our AML study demonstrate that many patients are achieving responses within the first two cycles, with fewer discontinuations overall due to adverse events compared to our MDS study, suggesting a prudent development path forward for the combination. "Based on these findings," continued Dr. Gold, "we will now begin to prepare for a Phase III registration study of Pracinostat and azacitidine in elderly patients with newly diagnosed AML, which we plan to initiate in the second half of 2016. We look forward to sharing more information regarding the design of this study in the months ahead."