Type-1 Interferon to Prevent Leukemia Relapse after Allogeneic Transplantation.

A potent graft-versus-leukemia (GVL) response is crucial in preventing relapse, the major impediment to successful allogeneic hematopoietic cell transplantation (HCT). In preclinical studies, Type-1 interferon (IFNα) enhanced cross-presentation of leukemia specific antigens by CD8α dendritic cells (DCs) and amplified GVL. This observation was translated into a proof-of-concept phase I/II clinical trial with long-acting IFNα (pegIFNα) in patients undergoing HCT for high-risk acute myeloid leukemia (AML). Patients with treatment resistant AML not in remission or poor risk leukemia were administered four dosages of pegIFNα every 14 days beginning at day -1 before HCT. Dose selection was established by adaptive design that continuously assessed the probability of dose limiting toxicities throughout the trial. Efficacy was evaluated by determining the six-month incidence of relapse at the maximum tolerated dose (MTD). Thirty-six patients (median age of 60 years) received pegIFNα treatment. Grade 3 or greater SAEs occurred in 25% of patients establishing 180mcg as the MTD. In phase II, the incidence of relapse was 39% at six-months, which was sustained through one-year post HCT. The incidence of transplant-related mortality was 13% and severe grade III-IV acute GVHD occurred in 11%. Paired blood samples from donors and recipients after HCT indicated elevated levels of Type-1 IFN with cellular response, persistence of cross-presenting DCs and circulating leukemia antigen specific T cells. These data suggest that prophylactic administration of pegIFNα is feasible in the peri-HCT period. In high-risk AML, increased toxicity was not observed with preliminary evidence for reduction in leukemia relapse after HCT.