A Study of Revumenib in R/R Leukemias Including Those With an MLL/KMT2A Gene Rearrangement or NPM1 Mutation

Phase 1: Oral revumenib; sequential cohorts of escalating dose levels of revumenib to identify the MTD and RP2D. Participants will be enrolled in one of six dose-escalation arms: Arm A: Participants not receiving any strong cytochrome P450 3A4 (CYP3A4) inhibitor/inducers or fluconazole. Arm B: Participants receiving itraconazole, ketoconazole, posaconazole, or voriconazole (strong CYP3A4 inhibitors) for antifungal prophylaxis. Arm C: Participants receiving revumenib and cobicistat. Arm D: Participants receiving fluconazole (moderate CYP3A4 inhibitor) for antifungal prophylaxis. Arm E: Participants not receiving any weak, moderate, or strong CYP3A4 inhibitors/inducers. Arm F: Participants receiving isavuconazole (moderate CYP3A4 inhibitor) for antifungal prophylaxis. 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: * Cohort 2A: Participants with KMT2Ar acute lymphoblastic leukemia (ALL)/mixed phenotype acute leukemia (MPAL) * Cohort 2B: Participants with KMT2A AML * Cohort 2C: Participants with NPM1m AML * Cohort 2D: Participants with acute leukemia (including KMT2Ar, NPM1m, NUP98r and other acute leukemias expected to have HOX/MEIS upregulation)