Anti-Tumor Effects of Gilteritinib on FLT3 Mutations: Insights into Resistance Mechanisms in Ba/F3 Cell Models

Taisuke Nakazawa, Hirofumi Tsuzuki, Tatsuya Kawase, Masamichi Mori, Taku Yoshida Astellas Pharma Inc, Ibaraki, JapanCorrespondence: Taisuke Nakazawa, Astellas Pharma Inc, 21 Miyukigaoka, Tsukuba-shi, Ibaraki, 305-8585, Japan, Tel +81-29-829-6288, Fax +81-29-852-2955, Email [email protected]: The efficacy of Fms-like tyrosine kinase 3 (FLT3) inhibitors has been well established against acute myeloid leukemia (AML) with FLT3 internal tandem duplication (FLT3-ITD) mutations. However, comparative data on the available inhibitors are limited, and drug resistance remains a major concern.Methods: This study examined the inhibitory effects of gilteritinib, quizartinib and midostaurin on Ba/F3 cells with FLT3-ITD mutations, or point mutations in the tyrosine kinase domain (TKD-PM) or juxtamembrane domain (JMD-PM), both in vitro and in vivo. Quizartinib and midostaurin were selected as comparators due to their clinical relevance in the AML setting and differing mechanisms of action.Results: Gilteritinib showed similar or superior growth inhibition against the majority of FLT3-TKD-PM or FLT3-JMD-PM cells compared to FLT3-ITD-mutant cells. In contrast, the inhibitory effects of quizartinib were reduced on cells with most types of FLT3-TKD-PM, and the inhibitory effects of midostaurin were attenuated on cells with FLT3-TKD-PM N676K. Gilteritinib also effectively suppressed FLT3 autophosphorylation and phosphorylation of signal transducer and activator of transcription 5 (STAT5), AKT and extracellular signal-regulated kinase (ERK) in FLT3-TKD-PM cells, while quizartinib showed a reduced inhibitory effect on FLT3 autophosphorylation and phosphorylation of downstream signaling molecules in FLT3-TKD-PM cells. In mice xenografted with Ba/F3 cells expressing FLT3-ITD mutations or FLT3-TKD-PM, gilteritinib showed a potent antitumor effect, whereas the antitumor effect of quizartinib was significantly diminished in the FLT3-TKD-PM xenograft model.Conclusion: These findings highlight the potent efficacy of gilteritinib against a wide range of FLT3 mutations, including TKD-PM and JMD-PM, as well as those associated with resistance to quizartinib or midostaurin. This comparative analysis underscores the need for tailored therapeutic strategies in AML treatment, emphasizing the clinical significance of gilteritinib in overcoming drug resistance.Keywords: acute myeloid leukemia, gilteritinib, FLT3-TKD, FLT3-JMD, drug resistance, xenograft mouse models