Hypomethylating Agents in Combination with Venetoclax As a Bridge to Allogeneic Transplant in Acute Myeloid Leukemia

Introduction Older adults with AML are often ineligible for high intensity chemotherapy and potentially curative allogeneic hematopoietic cell transplantation (HCT) due to poor performance status at presentation, comorbidities, and/or adverse genetic features associated with refractory disease and chemoresistance. Recently, the lower intensity combination of a hypomethylating agent and venetoclax (HMA/Ven) was shown to achieve durable responses in patients with AML. Despite this combination having been studied primarily in older, transplant-ineligible adults, a small subset of patients on the Phase 1b trial were successfully bridged to HCT (Pratz et al, 2019). We conducted a multi-center analysis assessing patient characteristics and clinical outcomes of patients treated with HMA/Ven who subsequently proceeded to HCT. Methods We retrospectively identified 51 adults who received HMA/Ven in either the front-line or relapsed/refractory (R/R) setting and underwent subsequent HCT between 2017 - 2019 at Stanford University, the University of California, San Francisco, and the University of California, Los Angeles. Patients received either azacitidine or decitabine in combination with venetoclax. Patients were evaluated for efficacy endpoints including: best response prior to HCT (complete remission [CR], CR with incomplete hematologic recovery [CRi], morphologic leukemia-free state [MLFS]), measurable residual disease (MRD) prior to HCT by flow cytometry (sensitivity threshold ≤1x10-4), and post-HCT relapse and survival. Results The median age at HCT was 65.5 years (24 - 76). Fifty-three percent of patients had a KPS of ≤ 80, and 29% had an HCT-CI of ³ 3. Fifty-seven percent had adverse-risk disease by 2017 European Leukemia Net criteria. The majority (63%) received decitabine; 23 (45%) received HMA/Ven as front-line induction and 28 (55%) for R/R disease. Compared to patients with R/R disease, patients who received front-line HMA/Ven were more likely to be older (67 vs 54 years, p = 0.003) and have a KPS ≤ 80 (65% vs 47%, p = 0.03). Patients with R/R disease had a median of 2 (1 - 4) lines of therapy prior to receiving HMA/Ven and 2 patients had undergone prior HCT. The number of HMA/Ven cycles prior to HCT varied considerably, with a median of 3 (1 - 11). The majority (78%) of patients achieved a complete remission prior to HCT. Of the patients who received front-line HMA/Ven, 83% achieved CR, 13% CRi, and 4% MLFS; 17 (74%) patients had a pre-HCT MRD assessmen