Outcomes of HMA and Venetoclax in Relapsed AML Post-Allogenic Hematopoietic Stem Cell Transplant

Background:

There is no standard of care treatment for Acute Myeloid Leukemia (AML) in relapse post-allogeneic hematopoietic stem cell transplant (post-HSCT), with overall 5-year survival about 5-10%. Venetoclax (Ven) is a novel BCL2 inhibitor approved by the FDA for treatment of newly diagnosed AML in combination with hypomethylating agents (HMA) or low dose cytarabine for patients unfit for intensive induction. However, data in relapsed/refractory AML are limited, especially in the post-HSCT setting. In this retrospective study, we reviewed outcomes of patients with AML relapse post-HSCT who received Ven in combination with HMA in a single center.

Methods:

Charts of 17 patients who had AML relapse post-HSCT treated with combination of Ven and HMA between November 2018 - March 2020 at the University of Kansas Medical Center were reviewed. We utilized descriptive statistics for baseline characteristics and outcomes, and Kaplan-Meier log-rank test for calculating overall survival.

Results

Seventeen patients received Ven+HMA for AML relapse post-HSCT in our center. At the time of SCT, patients were in first complete remission (CR) (n=15); second CR (n=1) and primary failure induction (1). Median age was 62 at time of relapse (31-71) years, and 8 patients were female (47%). 9 patients (53%) had adverse risk AML (ELN 2017) 8 of them were in CR1 and 1 with primary induction failure. Common mutations included DNMT3a, ASLX-1, TET2 (3); TP53 (2); IDH1/2 (2); NPM1/FLT3 (1); NPM1/IDH2 (1); NPM1 (1 transplanted in CR2); FLT3 (1). 2/17 had received Ven+HMA prior to SCT; 4 patients received HMA alone prior to SCT. 11 patients (65%) were naïve to either Ven or HMA prior to relapse. Median time to relapse was 181 (44-851) days post-HSCT. 9 (53%) patients received Azacitidine+Ven and 8 (47%) received Decitabine+Ven. HMA+Ven was the first line of therapy post-HSCT relapse in 14 patients. 2 had donor lymphocyte infusion (DLI) after either MEC or dacogen but relapsed prior to Ven+HMA. 1 had IDH (2) inhibitor. Patients received median of 2 (1-10) cycles of HMA+Ven. Six (35%) patients achieved complete remission/complete remission with incomplete hematologic recovery (CR/CRi), and 2/6 patients had negative measurable residual disease by multiparameter flow cytometry. Median overall survival was 361 days from relapse (Figure 1). 3/14 patients received subsequent DLI with Ven+HMA. Disease progression was the most common cause of death in 8/9 of patients who died during the follow up period. Most common side effects included neutropenic fever (n=8, 47%) and acute graft versus host disease (aGVHD) (n=5, 30%). 2/5 developed new aGVHD on HMA+Ven with no prior history of aGVHD. However, aGVHD was mainly grade I-II and responsive to therapy.

Discussion

HMA+Venetoclax demonstrates potential activity in patients with AML relapse post-HSCT with a CR/CRi rate of 35%, comparable to other salvage therapies. There were no unexpected side effect in this high-risk population. Larger studies are needed to confirm efficacy and toxicity in this setting.

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