Synthesis, in silico studies, and in vitro evaluation of novel isoindigo inhibitors targeting wild-type and D835Y mutant FLT3

Abstract

FMS-like tyrosine kinase 3 (FLT3) is a validated therapeutic target, but resistance mutations such as D835Y compromise its therapeutic utility by conferring resistance to existing inhibitors and limiting therapeutic options in FLT3-driven cancers, such as Acute Myeloid Leukemia (AML). In order to address this challenge and improve upon the modest activity of known isoindigo scaffolds against wild-type FLT3, this study reports the synthesis and docking of novel isoindigo-based derivatives targeting both wild-type and mutant (D835Y) FLT3. First, a series of 3-(2-oxoindolin-3-ylidene)indolin-2-one derivatives was synthesized through Sandmeyer isatin synthesis followed by Knoevenagel-type aldol condensation. Furthermore, molecular docking analysis indicated that the integration of a 1,3-dioxole moiety improves binding interactions within both the active and inactive kinase pockets and molecular dynamics analysis indicated the stability of the derivatives' virtual complexes. Moreover, in vitro assays identified derivatives 3, 5, 8, and 12 as potent nanomolar inhibitors of either or both FLT3 forms, as derivative 3 was the most potent dual inhibitor, with IC50 values of 243.3 nM against wild-type FLT3 and 121.3 nM against the D835Y mutant, while derivative 8 was the most potent against wild-type FLT3 (IC50 = 180.3 nM). These findings identify the optimized isoindigo scaffold as a promising chemical lead for the development of novel FLT3 inhibitors.