BRD4 and MYB Inhibition Overcomes Venetoclax Resistance in EVI1-rearranged Acute Myeloid Leukemia

EVI1-rearranged acute myeloid leukemia (AML) with inv(3)(q21q26) or t(3;3)(q21q26) represents a distinct and aggressive subtype characterized by poor prognosis and limited treatment options. However, the optimal strategy to overcome resistance to conventional therapy remains elusive. Building upon observations correlating EVI1 overexpression with reduced sensitivity to venetoclax, a BH3-mimetic inhibitor, we investigated the mechanisms of resistance to venetoclax in combination with hypomethylating agents in inv(3)/t(3;3) AML cells. Utilizing novel murine models recapitulating inv(3) AML with concomitant SF3B1 mutations, we conducted comprehensive phenotypic and transcriptomic analyses in the presence or absence of venetoclax-containing therapy. Despite initial therapeutic responses, manifested as partially prolonged survival and myeloid differentiation, resistant leukemic cells demonstrated enhanced dependency on BRD4 and MYB pathways with a dormant phenotype. Notably, inhibition of either BRD4 or MYB significantly augmented the efficacy of venetoclax and hypomethylating agents in both murine and patient-derived AML models harboring inv(3) and SF3B1 mutations. These findings elucidate the transcriptional dynamics underlying venetoclax resistance and propose alternative therapeutic strategies targeting BRD4 and MYB as promising avenues for improving outcomes in patients with EVI1-rearranged AML. Our work highlights the necessity for innovative combination therapies to address the multifaceted mechanisms of resistance in this high-risk leukemia subtype.