Phase II trial of cytarabine and mitoxantrone with devimistat in acute myeloid leukemia

Combining cytarabine and mitoxantrone with the tricarboxylic acid cycle inhibitor devimistat has been reported in a phase I clinical trial with relapsed or refractory acute myeloid leukaemia (AML). Here, the authors report the outcomes of a phase II study, analyse samples from both phases and perform preclinical analyses that show mitochondrial fission or autophagy inhibition sensitizes AML cells to devimistat. Devimistat is a TCA cycle inhibitor. A previously completed phase I study of devimistat in combination with cytarabine and mitoxantrone in patients with relapsed or refractory AML showed promising response rates. Here we report the results of a single arm phase II study (NCT02484391). The primary outcome of feasibility of maintenance devimistat following induction and consolidation with devimistat in combination with high dose cytarabine and mitoxantrone was not met, as maintenance devimistat was only administered in 2 of 21 responders. The secondary outcomes of response (CR + CRi) and median survival were 44% (21/48) and 5.9 months respectively. There were no unexpected toxicities observed. An unplanned, post-hoc analysis of the phase I and II datasets suggests a trend of a dose response in older but not younger patients. RNA sequencing data from patient samples reveals an age-related decline in mitochondrial gene sets. Devimistat impairs ATP synthesis and we find a correlation between mitochondrial membrane potential and sensitivity to chemotherapy. Devimistat also induces mitochondrial reactive oxygen species and turnover consistent with mitophagy. We find that pharmacological or genetic inhibition of mitochondrial fission or autophagy sensitizes cells to devimistat. These findings suggest that an age related decline in mitochondrial quality and autophagy may be associated with response to devimistat however this needs to be confirmed in larger cohorts with proper trial design.

Automated summary

This study reports the results of a phase II study that combines devimistat with cytarabine and mitoxantrone in patients with relapsed or refractory AML. The study found that inhibition of mitochondrial fission or autophagy sensitizes AML cells to devimistat. Additionally, an age-related decline in mitochondrial quality and autophagy may be associated with response to devimistat.