Asterias Biotherapeutics, Inc. (NYSE MKT: AST), a biotechnology company focused on the emerging field of regenerative medicine, today announced positive, new, long-term follow-up data from a Phase 2 clinical trial of AST-VAC1 in patients with intermediate and high risk acute myelogenous leukemia (AML). AST-VAC1 is the Company's autologous (using cells sourced from the patient) telomerase-based dendritic cell cancer vaccine. AML is the most common form of acute leukemia in adults with 12,000 new cases diagnosed annually, and remains an unmet clinical need, especially in patients over the age of 60 who face poor outcomes and have limited therapies available to them. The long-term follow-up showed that more than 50% of patients who received AST-VAC1 had prolonged relapse-free survival, even patients with high-risk AML including those over 60 years old and patients in second remission.
H. Jean Khoury, MD, FACP, professor of hematology and medical oncology, and director of the Division of Hematology in the Department of Hematology and Medical Oncology at Emory University School of Medicine, presented the new long-term follow-up findings at the 2015 American Society of Clinical Oncology (ASCO) Annual Meeting during an oral presentation on Saturday, May 30, 2015.
"Many AML patients in complete remission following chemotherapy eventually relapse due to a substantial burden of remaining leukemic cells," said Dr. Khoury. "Additional therapies that are well-tolerated are needed for patients at high risk of relapse. The long-term follow-up data shows that patients tolerated AST-VAC1 treatment very well, and more importantly, relapse-free survival in this high-risk patient population continues to be encouraging. Eleven out of 19 patients (58 percent) receiving AST-VAC1 during complete remission were relapse-free with a median follow-up of 52 months. More importantly, four out of seven patients (57 percent) over the age of 60 remained in remission after a median 54 months of follow-up. These results suggest that targeting telomerase through a dendritic cell-based vaccine approach may prolong remission duration in patients with high-risk AML, and warrant additional study in future trials."
"AST-VAC1 represents the first development product from our proprietary dendritic cell immunotherapy technology platform that is designed to stimulate patients' immune systems to attack telomerase, a protein that is expressed in over 95 percent of cancers but is rarely expressed in normal adult cells," said Dr. Jane Lebkowski, President of R&D of Asterias. "Our dendritic cell immunotherapy technology is based on a unique mode of action that is complementary and potentially synergistic to immune checkpoint inhibitor drugs that have shown promising results in treating patients across multiple advanced cancers. These positive long-term findings provide additional clinical rationale that supports our focus on progressing our AST-VAC2 allogeneic (non-patient specific) dendritic cell cancer vaccine development program into a Phase 1/2a clinical trial in lung cancer, as well as pursue development strategies for the AST-VAC1 program."
Long-Term Follow-Up Results
Twenty-one patients received at least three injections of AST-VAC1 in the study, including 19 patients in clinical remission (CR); 16 in first clinical remission (CR1) and three in second clinical remission (CR2), and two patients in early relapse. Seven of the 19 patients in CR were at least 60 years old at the time of immunotherapy with AST-VAC1. Of the 19 patients who were in CR, 13 received all 12 doses of AST-VAC1 with one additional patient withdrawing consent just before the last vaccination dose. The two patients who were vaccinated with AST-VAC1 during early relapse progressed rapidly and did not receive the full dosing regimen.
Eleven of 19 patients (58 percent) in the trial remain in CR with a median duration of follow-up of 52 months from first vaccination. Four of the seven patients who were at least 60 years old at the time of immunotherapy with AST-VAC1 remain relapse free 52 to 59 months from first vaccination. The three patients who received AST-VAC1 while in CR2 were in remission as of their last follow-up of 24, 50 and 59 months. Historical results suggest that relapse-free survival in AML patients greater than 60 years old is poor with 10 percent to 20 percent surviving 60 months.
Patient immune response to telomerase after vaccination with AST-VAC1 was assessed by peptide ELISpot analysis to measure the presence of activated T-cells specific to hTERT. Positive immune responses were detected in 58% of patients.
AST-VAC1 was found to be safe and well-tolerated in this study over multiple vaccinations, with up to 32 serial vaccinations administered (median = 17). Idiopathic thrombocytopenic purpura (grade 3-4) was reported in one patient. Other toxicities (grade 1-2) included rash or headache.
"We are very encouraged by these promising new, long-term relapse findings, and excited by the opportunity of having a third clinical stage program at Asterias," said Pedro Lichtinger, President and CEO of Asterias. "AST-VAC1 becomes our most advanced clinical opportunity fitting our strategic focus on major unmet medical needs without adequate available therapies. We are forming our clinical development plan for AST-VAC1, and intend to explore all strategic alternatives to further advance this product for the benefit of patients, and to maximize value for Asterias shareholders."
Asterias Biotherapeutics, Inc.