Enasidenib, an inhibitor of mutant IDH2 proteins, induces durable remissions in older patients with newly diagnosed acute myeloid leukemia

Older adults with acute myeloid leukemia (AML) who are not fit for standard chemotherapy historically have poor outcomes. Approximately 12-15% of older patients with AML harbor isocitrate dehydrogenase 2 (IDH2) gene mutations. Enasidenib is an oral inhibitor of mutant IDH2 proteins. Among 39 patients with newly diagnosed mutant-IDH2 AML who received enasidenib monotherapy in this phase I/II trial, median age was 77 years (range 58-87) and 23 patients (59%) had had an antecedent hematologic disorder. The median number of enasidenib treatment cycles was 6.0 (range 1-35). The most common treatment-related adverse events were indirect hyperbilirubinemia (31%), nausea (23%), and fatigue, decreased appetite, and rash (18% each). Treatment-related grade 3-4 cytopenias were reported for eight patients (21%); there was no treatment-related grade 3-4 infections. Twelve patients achieved a response (overall response rate 30.8% [95% CI 17.0%, 47.6%]), including seven patients (18%) who attained complete remission. At a median follow-up of 8.4 months, the median duration of any response was not reached (NR). Median overall survival for all patients was 11.3 months (95% CI 5.7, 15.1), and was NR for responders. Oral, outpatient targeted treatment with enasidenib may benefit older adults with newly diagnosed mutant-IDH2 AML who are not candidates for cytotoxic regimens.