In vitro activity: PD 166866 inhibits human full-length FGFR-1 tyrosine kinase with an IC50 value of 52.4 nM and is characterized as an ATP competitive inhibitor of the FGFR-1. PD 166866 is a potent inhibitor of FGFR autophosphorylation in NIH 3T3 cells expressing endogenous FGFR-1 and in L6 cells overexpressing the human FGFR-1 tyrosine kinase. PD 166866 also inhibits bFGF-induced tyrosine phosphorylation of the 44- and 42-kDa (ERK 1/2) mitogen-activated protein kinase isoforms in L6 cells. Daily exposure of PD 166866 to L6 cells at concentrations from 1 to 100 nM results in a concentration-related inhibition of bFGF-stimulated cell growth for 8 consecutive days with an IC50 value of 24 nM.

Kinase Assay: PD166866, a member of a new structural class of tyrosine kinase inhibitors, the 6-aryl-pyrido[2,3-d]pyrimidines, is a a new nanomolar potent and selective small molecule inhibitor of FGFR (fibroblast growth factor-1 receptor) tyrosine kinase inhibitor with an IC50 of 52.4 nM. PD 166866 is a potent inhibitor of FGFR autophosphorylation in NIH 3T3 cells expressing endogenous FGFR-1 and in L6 cells overexpressing the human FGFR-1 tyrosine kinase. PD 166866 also inhibits bFGF-induced tyrosine phosphorylation of the 44- and 42-kDa (ERK 1/2) mitogen-activated protein kinase isoforms in L6 cells. PD 166866has potential use as antiproliferative/antiangiogenic agent for such therapeutic targets as tumor growth and neovascularization of atherosclerotic plaques.

Cell Assay: PD 166866 is dissolved in DMSO. PD 166866 or vehicle (0.5% DMSO, final concentration) are added every day to triplicate cultures of cells together with 25 ng/mL bFGF to stimulate FGF-driven growth. In some experiments, PD 166866 is added every day to triplicate cultures of cells together with 30 ng/mL PDGF-BB to stimulate PDGF-driven growth. Cell number is measured by Coulter counting on days 1, 3, 6 or 8 after drug exposure.