In total, 80 patients, including 18 pediatric patients, with R/R KMT2A-r acute leukemias (AML and ALL) were treated across six dose-escalation cohorts, and a RP2D of 276 mg twice a day, without a strong CYP3A4 inhibitor, was established (for patients treated with strong CYP3A4 inhibitors, i.e., azoles, the RP2D was 163 mg twice a day). The gene discussed is CYP3A4; the disease is acute myeloid leukemia.