Prophylactic maintenance with venetoclax/azacitidine after reduced intensity conditioning allo-transplant for high risk MDS and AML.

We conducted a phase 1 trial assessing safety and efficacy of prophylactic maintenance therapy with venetoclax and azacitidine (Ven/Aza) in patients with high risk myelodysplastic syndromes (MDS)/acute myeloid leukemia (AML) undergoing reduced intensity allogeneic hematopoietic stem cell transplantation following venetoclax and FluBu2-conditioning (Ven/FluBu2 allo-SCT) with tacrolimus and methotrexate as graft-versus-host disease (GVHD) prophylaxis. Among 27 patients who underwent Ven/FluBu2 allo-SCT (55.6% prior venetoclax exposure and 96% molecular measurable residual disease (MRD)-positive), 22 received maintenance therapy with azacitidine 36 mg/m2 intravenously on days 1-5 and venetoclax 400 mg by mouth on days 1-14 on one of two schedules (42-day cycles x 8 or 28-day cycles x 12). During maintenance, the most common grade 3/4 adverse events were leukopenia, neutropenia and thrombocytopenia, which were transient and manageable. Infections were uncommon (n=4, all grade 1-2). The 1-year and 2-year moderate/severe chronic GVHD rates were 4% (95% CI, 0.3-18%) and 22% (95% CI, 9-40%). After a median follow-up of 25-months among survivors, median overall survival (OS) was not reached. In the 22 patients who received Ven/Aza maintenance, the 2-year OS, progression-free survival, non-relapse mortality, and cumulative incidence of relapse rates were 67% (95% CI, 43-83%), 59% (95% CI, 36-76%), 0%, and 41% (95% CI, 20-61%), respectively. Immune monitoring demonstrated no significant impact on T cell expansion, but identified reduced B cell expansion compared to controls. This study demonstrates prophylactic Ven/Aza maintenance can be safely administered in high risk MDS/AML patients, but a randomized study is required to properly assess any potential benefit. (NCT03613532).