SGX-523 is a selective Met inhibitor with IC50 of 4 nM, no activity to BRAFV599E, c-Raf, Abl and p38α. 

SGX-523 belongs to the class of c-Met/hepatocyte growth factor receptor (HGFR) tyrosine kinase inhibitors. SGX-523 stabilizes MET in a unique inactive conformation that is inaccessible to other protein kinases, suggesting an explanation for its selectivity. SGX523 potently inhibits the purified MET catalytic domain but not the closely related receptor tyrosine kinase RON. SGX523 indicates ATP-competitive inhibition with higher apparent affinity for the less active, unphosphorylated form of MET [MET-KD(0P), with a Ki of 2.7 nM] versus the more active phospho-enzyme [MET-KD(3P), with a Ki of 23 nM], a phenomenon consistent with preferential binding to an inactive enzyme conformation. SGX523 inhibits MET-mediated signaling, cell proliferation and cell migration at nanomolar concentrations but had no effect on signaling dependent on other protein kinases, including the closely related RON, even at micromolar concentrations.