Phase 2 Study of Interferon-Gamma and Donor Lymphocyte Infusion for the Treatment of Relapsed Myeloid Malignancies after Allogeneic Stem Cell Transplantation

Project Summary/Abstract Allogeneic stem cell transplantation (alloSCT) is a potentially curative therapy for acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). Donor-derived alloreactive T cells can kill recipient leukemia cells, mediating the graft-vs-leukemia effect (GVL). GVL failure leads to post-

transplant relapse, affecting 30-40% of alloSCT recipients and leading to extremely poor prognosis, with a median survival of 6 months. The clinical sensitivity of leukemias to GVL varies by disease type. Dr. Shlomchik, Co-PI, sought the mechanism of GVL resistance using preclinical GVL models and discovered that myeloblastic leukemia required the expression of

the IFN-γ receptor for GVL. Two independent groups reported lower levels of human leukocyte antigen (HLA) expression in myeloid blasts post-transplant relapse, which IFN-γ can restore in vitro. These data supported conducting a phase 1 trial to evaluate the safety of IFN-γ (ACTIMMUNE®) in AML/MDS patients with post-transplant relapse (NCT04628338). 4 out of 6

patients who received IFN-γ and subsequent donor leukocyte infusion (DLI) achieved durable complete remissions with full donor hematopoiesis recovery. Given these favorable results, we propose a multicenter phase 2 trial to evaluate the efficacy of IFN-γ/DLI compared to the outcomes in a synthetic control generated from the Center for International Blood and Marrow

Transplant Research (CIBMTR) database. Patients with AML/MDS who developed relapse with >5% bone marrow myeloblasts after an HLA-matched alloSCT will be eligible. Subjects will receive 100mcg of IFN-γ thrice weekly by self-subcutaneous injection for four weeks. If IFN-γ is tolerated, subjects will receive DLI concurrently with IFN-γ for eight more weeks to complete the

12-week treatment intervention. The primary objective is to evaluate the efficacy of IFN-γ/DLI, measured by event-free survival at 1-year. The secondary objectives are to evaluate the safety and efficacy of IFN-γ/DLI measured by secondary endpoints, including measurable disease- negative complete remission at 6 months and overall survival at 12 months. The incidence of

steroid and ruxolitinib-refractory graft-versus-host disease will be used for the stopping rule. 45 participants will be enrolled to receive IFN-γ/DLI. The major clinical endpoints will be compared to 3 CIBMTR synthetic cohorts of patients treated with 1) chemotherapy only, 2) chemotherapy+ DLI, or 3) DLI only. Each control group will have 135 subjects (1:3 ratio of treated subjects). In

exploratory studies, we will analyze IFN-γ induced transcriptomic changes in leukemic and immune cells to find the biomarkers that could be used to select subjects for future studies.