Study of Iadademstat and Gilteritinib in Patients With R/R AML With FMS-like Tyrosine Kinase Mutation (FLT3 Mut+)

Main Inclusion Criteria: * Diagnosis of primary AML or AML with myelodysplasia-related changes (AML-MRC) * Patient is in first or second relapse or has refractory disease. Patients must have had histologic verification of AML at the original diagnosis. * Patient must be positive for the following FLT3 mutations in bone marrow or PB: FLT3 internal tandem duplication (ITD), FLT3 tyrosine kinase domain (TKD) D835 or I836 or FLT3-ITD and specified FLT3-TKD. * ECOG performance status 0-2 * Life expectancy of at least 3 months in the opinion of the investigator. * Normal hepatic and renal function. * Patient is able to swallow oral medications. * Female patients are postmenopausal, documented as surgically sterile, use two methods of contraception or practice true abstinence and have a negative urine pregnancy test at screening. * Male patients even if surgically sterilized agree to practice true abstinence or use highly effective barrier contraception. Main Exclusion Criteria: * Diagnosis of acute promyelocytic leukemia. * Known BCR-ABL-positive leukemia. * AML secondary to prior chemotherapy for other neoplasms (except for MDS). * AML that has relapsed after or is refractory to more than 2 lines of therapy. * Clinically active central nervous system leukemia or prior history of NCI CTCAE Grade ≥ 3 drug-related CNS toxicity. * Major surgery or radiation therapy within 4 weeks prior to the first study dose. * Prior treatment with iadademstat is not allowed. Treatment with any other agents with KDM1A/LSD1 inhibitory activity is only allowed if treatment finalized at least 3 weeks prior to first dose on study. Previous treatment with FLT3 inhibitors is allowed in the following cases: midostaurin and sorafenib are allowed when used in first-line therapy regimen as part of induction, consolidation and/or maintenance: quizartinib and gilteritinib are allowed when used in first-line therapy regimen, as part of induction, consolidation and/or maintenance, ONLY if patients were not refractory to the drugs or if responding, relapse did not occur while on these drugs. * Patients not eligible to receive gilteritinib per label. * Prior treatment with 3 or more lines of AML therapy. * Treatment with any investigational products within 3 weeks prior to first dose of study treatment. * Uncontrolled hypertension or poorly controlled diabetes. * Evidence of active uncontrolled viral, bacterial, or systemic fungal infection. * Pregnant or lactating women.