A PI3K Inhibitor with Low Cardiotoxicity and Its Synergistic Inhibitory Effect with Gilteritinib in Acute Myelogenous Leukemia (AML) Cells.

N-(2-chloro-5-(3-(pyridin-4-yl)-1H-pyrazolo [3,4-b]pyridin-5-yl)pyridin-3-yl)-4-fluorobenzenesulfonamide, namely, FD274, is a promising 7-azaindazole-based PI3K inhibitor candidate with high antitumor efficacy against acute myeloid leukemia and reduced cardiotoxicity in the zebrafish model. To advance its clinical translation, in this work, we conducted comprehensive assessments of the cardiotoxicity of FD274 and preliminarily investigated its synergistic antitumor effects with an FLT3 inhibitor, Gilteritinib. The cardiotoxicity profile of FD274, as well as its bioisostere FD268 (positive control), was evaluated using the C57BL/6 mouse model and the H9C2 cell line. The cardiotoxicity of FD274 after a consecutive 20-day treatment period was further assessed in an HL-60 xenograft mouse model. The synergistic cytotoxicity of FD274 with Gilteritinib was evaluated in the HL-60 cell line and the FLT3-ITD cell line MV-4-11. FD274 demonstrated lower adverse effects associated with cardiac dysfunction, oxidative stress, and myocardial injury in the C57BL/6 mouse model and in the H9C2 cell line as compared with FD268. Its negligible adverse effect was further validated in the HL-60 xenograft mice after the 20-day treatment process. Moreover, FD274 demonstrated a synergistic pro-apoptotic effect with Gilteritinib in both HL-60 and MV-4-11 cells. Our findings confirmed the low cardiotoxicity of FD274 and its great potential for combination therapy with Gilteritinib, warranting further development.