PF-573228 is an ATP-competitive FAK inhibitor. In a cell-free assay, the IC50 of FAK is 4 nM.

Affinity determination: Purified activated FAK kinase domain (amino acids 410–689) is reacted with 50 μM ATP, and 10 μg/well of a random peptide polymer of Glu and Tyr (molar ratio of 4:1), poly(Glu/Tyr) in kinase buffer (50 mM HEPES, pH 7.5, 125 mM NaCl, 48 mM MgCl2) for 15 min. Phosphorylation of poly(Glu/Tyr) is challenged with serially diluted compounds at 1/2-Log concentrations starting at a top concentration of 1 μM. Each concentration is run in triplicate. Phosphorylation of poly(Glu/Tyr) is detected with a general anti-phospho-tyrosine (PY20) antibody, followed by horseradish peroxidase-conjugated goat anti-mouse IgG antibody. The standard horseradish peroxidase substrate 3, 3', 5, 5'-tetramethylbenzidine is added, and Optical Density readings at 450 nm are obtained following the addition of stop solution (2 M H2SO4). The IC50 values are determined using the Hill slope model.

Growth assays are performed by seeding 1 × 104 REF52 or PC3 cells/well of a 24-well plate in triplicate 24 h prior to daily treatment with the indicated concentrations of each inhibitor for 3 days. Subsequently, the cells are harvested and counted.(Only for Reference)