NVS-MELK8a

NVS-MELK8a reported in this work presents a useful addition to the chemical tools for MELK. NVS-MELK8a showed potent (low nanomolar) biochemical kinase activity inhibition for both kinase domain and full length MELK. NVS-MELK8a MELK engagement was further confirmed by SPR (low nanomolar KD). A KINOMEscan panel revealed a reasonably selective profile for NVS-MELK8a, with only ten other kinases inhibited at 1 uM. The next most inhibited kinase is FLT3, which exhibited an IC50 = 0.18 uM, about ~90-fold less potent than NVS-MELK8a inhibition for MELK. This presents an advantage over the previously reported MELK probe JNJ-47117096, which demonstrated equipotent nanomolar inhibition of FLT3 and MELK. Selective cellular MELK activity was further demonstrated through the use of differentially MELK expressed cell lines, whereby NVS-MELK8a exhibited 10-fold greater growth inhibition for a MELK dependent cell line (MDA-MB-468) vs MELK independent cell line (MCF7), which phenocopied the growth inhibition effect of MELK shRNA knockdown in MDA-MB-468. NVS-MELK8a should be used at a maximum of 100 nM concentration in cells, to avoid potential effects driven by FLT3 inhibition.