Phase 1: Oral SNDX-5613; sequential cohorts of escalating dose levels of SNDX-5613 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 SNDX-5613 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 3 indication-specific expansion cohorts to determine the efficacy, short- and long-term safety, and tolerability of SNDX-5613:~Cohort 2A: Participants with MLLr acute lymphoblastic leukemia (ALL)/mixed phenotype acute leukemia (MPAL)~Cohort 2B: Participants with MLLr AML~Cohort 2C: Participants with NPM1c AML
Phase 1 dose escalation will determine the maximum tolerated dose (MTD) and recommended Phase 2 dose (RP2D) of SNDX-5613 in participants with acute leukemia.~In Phase 2, participants will be enrolled in 3 indication-specific expansion cohorts to determine the efficacy, short- and long-term safety, and tolerability of SNDX-5613.