RecruitingDrug trialA Study of Revumenib in R/R Leukemias Including Those With an MLL/KMT2A Gene Rearrangement or NPM1 MutationPhase 1 dose escalation will determine the maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D) of revumenib in participants with acute leukemia. In Phase 2, participants will be enrolled in 4 indication-specific expansion cohorts to determine the efficacy, short- and long-term safety, and tolerability of revumenib.