Safety of gemtuzumab ozogamicin with cytarabine, daunorubicin, and midostaurin induction in FLT3-mutated AML

This phase 1 study investigated the addition of gemtuzumab ozogamicin (GO) to intensive chemotherapy with cytarabine, daunorubicin, and midostaurin in 21 patients with newly diagnosed (ND) FMS-like tyrosine kinase 3 (<i>FLT3</i>)-mutated acute myeloid leukemia (AML). Four dose levels of GO were evaluated. The use of GO was tolerable, with all dose-limiting toxicities similar to those seen in standard-of-care treatment. After induction, the median time to platelet recovery was 26 days, and the median time to absolute neutrophil count (ANC) recovery was 27 days. The maximum tolerated dose was cytarabine 100 mg/m² on days 1 to 7, midostaurin 50 mg twice daily on days 8 to 21, daunorubicin 60 mg/m² on days 1 to 3, and GO 3 mg/m² on days 1 and 4. For the 18 patients who were evaluable for response after induction therapy, 16 patients (76%) achieved a composite complete response (complete remission [CR] + CR with incomplete hematologic recovery), and 2 (10%) had stable disease. Of the 14 patients who proceeded to consolidation, 5 discontinued the study for transplant, 1 for disease progression, and 1 for physician discretion. Seven patients completed consolidation therapy, all of whom achieved a CR. In total, 13 of the 21 patients (62%) received a hematopoietic stem cell transplant. Our results show that GO can safely be combined with intensive chemotherapy with midostaurin in ND, <i>FLT3</i>-mutated AML. This trial was registered at www.clinicaltrials.gov as #NCT03900949.