Identification of novel lysine demethylase 5-selective inhibitors by inhibitorbased fragment merging strategy

Histone lysine demethylases (KDMs) have drawn much attention as targets of therapeutic agents. KDM5 proteins, which are Fe(II)/alpha-ketoglutarate-dependent demethylases, are associated with oncogenesis and drug resistance in cancer cells, and KDM5-selective inhibitors are expected to be anticancer drugs. However, few cellactive KDM5 inhibitors have been reported and there is an obvious need to discover more. In this study, we pursued the identification of highly potent and cell-active KDM5-selective inhibitors. Based on the reported KDM5 inhibitors, we designed several compounds by strategically merging two fragments for competitive inhibition with a-ketoglutarate and for KDM5-selective inhibition. Among them, compounds 10 and 13, which have a 3-cyano pyrazolo[ 1,5-alpha] pyrimidin-7-one scaffold, exhibited strong KDM5-inhibitory activity and significant KDM5 selectivity. In cellular assays using human lung cancer cell line A549, 10 and 13 increased the levels of trimethylated lysine 4 on histone H3, which is a specific substrate of KDM5s, and induced growth inhibition of A549 cells. These results should provide a basis for the development of cell-active KDM5 inhibitors to highlight the validity of our inhibitor-based fragment merging strategy.