In vitro activity: PHA-665752 significantly inhibits c-Met kinase activity with Ki of 4 nM, and exhibits>50-fold selectivity for c-Met compared with various tyrosine and serine-threonine kinases. PHA-665752 potently inhibits the HGF-stimulated c-Met autophosphorylation with IC50 of 25-50 nM. PHA-665752 also significantly blocks HGF- and c-Met-dependent functions such as cell motility and cell proliferation with IC50 of 40-50 nM and 18-42 nM, respectively. In addition, PHA-665752 potently inhibits HGF-stimulated or constitutive phosphorylation of mediators of downstream of c-Met such as Gab-1, ERK, Akt, STAT3, PLC-γ, and FAK in multiple tumor cell lines. PHA-665752 inhibits cell growth in TPR-MET-transformed BaF3 cells with IC50 of<60 nM, and inhibits constitutive cell motility and migration by 92.5% at 0.2 μM. Inhibition of c-Met by PHA665752 (0.2 μM) also induces cell apoptosis of 33.1% and G1 cell cycle arrest with cells in G1 phase increasing from 42.4% to 77.0%. PHA665752 can cooperate with rapamycin to inhibit cell growth of TPR-MET-transformed BaF3 cells and non-small cell lung cancer H441 cells.

Kinase Assay: The c-Met kinase domain GST-fusion protein is used for the c-Met assay. The IC50 value of PHA-665752 for the inhibition of c-Met is based on phosphorylation of kinase peptide substrates or poly-glu-tyr in the presence of ATP and divalent cation (MgCl2 or MnCl2 10-20 mM). The linear range (i.e., the time period over which the rate remains equivalent to the initial rate) is determined for c-Met, and the kinetic measurement and IC50 determination are performed within this range.

Cell Assay: For proliferation assays, cells (S114, GTL-16, NCI-H441, and BxPC-3) are grown in medium with 0.1% FBS for 48 hours after which they are treated with various concentrations of PHA-665752 in HGF (50 ng/mL) in a medium containing 2% FBS. After 18 hours, cells are incubated with BrdUrd for 1 hour, fixed, and stained with anti-BrdUrd peroxidase-conjugated antibody, and plates are read at 630 nm. For apoptosis assays, cells are grown in medium with 2% FBS in presence and absence of HGF (50 ng/mL) and various concentrations of PHA-665752 for 72 hours. After 72 hours, a mixture containing ethidium bromide and acridine orange is added, and apoptotic cells (bright orange cells or cell fragments) are counted by fluorescence microscopy.

Cancer Res. 2003 Nov 1;63(21):7345-55; Clin Cancer Res. 2005 Mar 15;11(6):2312-9; Cancer Res. 2007 Apr 15;67(8):3529-34.