MCL1 inhibition to enhance the efficacy of MYB targeting in pediatric acute myeloid leukemia.

Outcomes for pediatric acute myeloid leukemia (AML) have improved significantly in recent years. However, relapsed and refractory disease remains a significant problem. The chemotherapy burden experienced by these patients makes the translational development of non-genotoxic experimental therapies attractive. We previously reported that the anti-helminth drug mebendazole induces degradation of the transcription factor MYB and has potent anti-AML activity. In the present study, we use CRISPR drop-out screening to identify genes encoding the proapoptotic regulators BAK and NOXA as hits conferring resistance to mebendazole activity in AML cells. Conversely, targeting MCL1 with a BH3-mimetic significantly enhanced the anti-AML activity of mebendazole in both AML cell lines in vitro and pediatric patient-derived xenograft (PDX) AML cells ex vivo. Treatment of mice transplanted with THP-1 AML cells or aggressive infant PDX AML cells with this drug combination significantly impaired disease progression in vivo. Our data indicate that mebendazole-induced MYB degradation in combination with MCL1 targeting is a novel non-genotoxic therapeutic strategy for pediatric AML.