Targeting gain of function and resistance mutations in Abl and KIT by hybrid compound design.

Mutations in the catalytic domain at the gatekeeper position represent the most prominent drug-resistant variants of kinases and significantly impair the efficacy of targeted cancer therapies. Understanding the mechanisms of drug resistance at the molecular and atomic levels will aid in the design and development of inhibitors that have the potential to overcome these resistance mutations. Herein, by introducing adaptive elements into the inhibitor core structure, we undertake the structure-based development of type II hybrid inhibitors to overcome gatekeeper drug-resistant mutations in cSrc-T338M, as well as clinically relevant tyrosine kinase KIT-T670I and Abl-T315I variants, as essential targets in gastrointestinal stromal tumors (GISTs) and chronic myelogenous leukemia (CML). Using protein X-ray crystallography, we confirm the anticipated binding mode in cSrc, which proved to be essential for overcoming the respective resistances. More importantly, the novel compounds effectively inhibit clinically relevant gatekeeper mutants of KIT and Abl in biochemical and cellular studies.