Background:Gilteritinib, an oral FMS-like tyrosine kinase 3 (FLT3) inhibitor, is approved for the treatment of adults with FLT3-mutated (FLT3mut+) relapsed or refractory (R/R) acute myeloid leukemia (AML) in the United States and many other countries/regions. However, not all respond to treatment and most patients eventually develop recurrent disease. Combining gilteritinib with other agents may improve response. Atezolizumab (840 mg intravenous [IV] every 2 weeks [Q2W]) + azacitidine demonstrated an overall response rate of 62% in hypomethylating agent-naive patients with higher-risk myelodysplastic syndrome (Gerds AT, et al. Blood. 2018;132[suppl 1]:466). Therefore, the safety and efficacy of combination therapy with gilteritinib and atezolizumab was investigated in an ongoing phase 1, open-label, single-arm, dose-escalation study (ClinicalTrials.gov identifier: NCT03730012) in adult patients with FLT3mut+R/R AML.