Discovery of tyrosine kinase inhibitors by docking into an inactive kinase conformation generated by molecular dynamics

Several small molecules that bind to the inactive DFG-out conformation of tyrosine kinases (called type II inhibitors) have shown a good selectivity profile over other kinase targets. To obtain a set of DFG-out structures, we performed an explicit solvent molecular dynamics (MD) simulation of the complex of the catalytic domain of a tyrosine kinase receptor, ephrin type-A receptor 3 (EphA3), and a manually docked type II inhibitor. Automatic docking of four previously reported type II inhibitors was used to select a single snapshot from the MD trajectory for virtual screening. High-throughput docking of a pharmacophore-tailored library of 175,000 molecules resulted in about 4 million poses, which were further filtered by van der Waals efficiency and ranked according to a force-field-based energy function. Notably, around 20 % of the compounds with predicted binding energy smaller than -10 kcal mol^-1 are known type II inhibitors. Moreover, a series of 5-(piperazine-1-yl)isoquinoline derivatives was identified as a novel class of low-micromolar inhibitors of EphA3 and unphosphorylated Abelson tyrosine kinase (Abl1). The in silico predicted binding mode of the new inhibitors suggested a similar affinity to the gatekeeper mutant T315I of Abl1, which was verified in vitro by using a competition binding assay. Additional evidence for the type II binding mode was obtained by two 300 ns MD simulations of the complex between N-(3-chloro-4-(difluoromethoxy)phenyl)-2-(4-(8-nitroisoquinolin-5-yl)piperazin-1-yl)acetamide and EphA3.

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