Purity >98%. LJH685 is an inhibitor of p90 ribosomal S6 kinases (RSKs, also known as MAP kinase-activated protein kinases, or MAPKAPKs) that inhibits RSK1, 2, and 3 in vitro with IC50 values of 6, 5, and 4 nM, respectively. It is selective for RSKs over a panel of 96 other kinases. LJH685 blocks RSK activity in cells, preventing phosphorylation of y-box-binding protein 1 on Ser102 . The inhibition of RSK activity correlates with antiproliferative effects in MAPK pathway-dependent cancer cell lines, but only in an anchorage-independent growth setting.