Onvansertib (NMS-1286937) is a PLK1 inhibitor (IC50=2 nM) with high selectivity and oral activity. Onvansertib has antitumor activity and inhibits tumor growth.

MELK:744 nM, PLK1:2 nM, FLT3:510 nM, CK2:826 nM

Kinase profile: The inhibitory activity of putative kinase inhibitors and the potency of selected compounds are determined using a trans-phosphorylation assay. Specific peptide or protein substrates are trans-phosphorylated by their specific serine-threonine or tyrosine kinase, in the presence of ATP traced with 33P-γ-ATP, at optimized buffer and cofactors conditions. At the end of the phosphorylation reaction, more than 98% unlabeled ATP and radioactive ATP is captured by adding an excess of the ion exchange dowex resin; the resin then settles down to the bottom of the reaction plate by gravity. Supernatant, containing the phosphorylated substrate, is subsequently withdrawn and transferred into a counting plate, followed by evaluation by b-counting. Inhibitory potency evaluation for all the tested kinases was performed at 25 °C using a 60 min end-point assay where the concentrations of ATP and substrates are kept equal to 2 x αKm and saturated (>5 x αKm), respectively.

Cells are seeded into 96- or 384-well plates at densities ranging from 10,000 to 30,000/cm2 for adherent and 100,000/mL for nonadherent cells in appropriate medium supplemented with 10% fetal calf serum. After 24 hours, cells were treated in duplicate with serial dilutions of NMS-P937, and 72 hours later, the viable cell number was assessed by the CellTiter-Glo Assay (Promega). IC50 values were calculated with a sigmoidal fitting algorithm (Assay Explorer MDL). Experiments were carried out independently at least twice.(Only for Reference)