Structure-Kinetic-Relationship Reveals the Mechanism of Selectivity of FAK Inhibitors Over PYK2

There is increasing evidence of a significant correlation between prolonged drug-target residence time and increased drug efficacy. Here, we report a structural rational for kinetic selectivity between two closely related kinases: Focal Adhesion Kinase (FAK) and Proline-rich Tyrosine Kinase 2 (PYK2). We found that slow off-rate FAK inhibitors induce helical structure at the DFG motif of FAK but not PYK2. Binding kinetic data, high resolution structures and mutagenesis data support the role of hydrophobic interactions of inhibitors with the DFG helical region providing a structural rational for slow dissociation rates from FAK and kinetic selectivity over PYK2. Our experimental data correlated well with computed relative residence times from molecular simulations providing a feasible strategy for rationally optimizing ligand residence times. We suggest that the interplay between the protein structural mobility and ligand-induced effects is a key regulator of the kinetic selectivity of inhibitors of FAK versus PYK2.