PF-431396 is a dual PYK2/FAK inhibitor (IC50: 11/2 nM).

PF-431396 consistently inhibits protein tyrosine kinase phosphorylation under both calcium deficiency and the presence of Ca/W-7. It also blocks tyrosine phosphorylation of Pyk2 and FAK induced by anti-Ig- and aggregated LFA-1 in A20 cells, thereby inhibiting B cell proliferation.

In Vitro Kinase Assays and Selectivity Screening : To measure Mps1 activity, 25 ng of recombinant, full-length enzyme is incubated in reaction buffer (50 mM Tris-HCl pH 7.5, 10 mM MgCl2, 0.01% Triton X-100 and 5 μM Myelin basic protein (MBP)) containing vehicle (DMSO alone) or inhibitors. Forty μM ATP (2xKm) is added with 1 μCi [γ-33P]ATP and the reaction is incubated at room temperature for 45 minutes. Reactions are terminated with 3% phosphoric acid and transferred to P81 filter plates. Samples are washed in 1% phosphoric acid and 33P radioactivity is measured on a TopCount scintillation reader. In-house kinase assays are all carried out at 2xKm ATP concentrations. MPI-0479605 (500 nM) is also screened against a larger kinase panel.