Identification of PKMYT1 inhibitors by screening the GSK published protein kinase inhibitor set I and II

As a member of the Wee-kinase family protein kinase PKMYT1 is involved in G2/M checkpoint regulation of the cell cycle. Recently, a peptide microarray approach led to the identification of a small peptide; EFS247-259 as substrate of PKMYT1, which allowed for subsequent development of an activity assay. The developed activity assay was used to characterize the PKMYT1 catalyzed phosphorylation of EFS247-259. For the first time kinetic parameters for PKMYT1, namely Km, Km, ATP and vmax were determined. The optimized assay was used to screen the published protein kinase inhibitor sets (PKIS I and II), two sets of small molecule ATP-competitive kinase inhibitors reported by GlaxoSmithKline. We identified ten inhibitors, providing different scaffolds. The inhibitors were further characterized by using binding assay, activity and functional assay. In addition, docking studies were carried out in order to rationalize the observed biological activities. The derived results provide the basis for further chemical optimization of PKMYT1 inhibitors and for further analysis of PKMYT1 as target for anti-cancer therapy.