Design, synthesis, activity and properties of selective inhibitors of focal adhesion kinase.
Authors: Michael J. Luzzio, Christopher Autry, Beth Cooper, Matt Griffor, Catherine Hulford, John Kath, Jing Lin, Eric Marr, Daniel Richter, W. Gregory Roberts, Ethan Ung, Felix Vajdos, Mathew Wessel, Pamela Whalen, Lili Yao
Journal: Cancer Research (2006)

5711   Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that localizes to focal adhesion plaques and is phosphorylated in response to integrin β1, β3, β5 binding to cellular ligands. FAK is the kinase signal transducer for integrins which when constitutively active inhibits anoikis allowing anchorage independent cell growth. The continuing growing body of FAK biology suggests that FAK is an important target for anticancer chemotherapy and necessitated the need to further investigate the development of FAK inhibitors. We previously reported that PF-941222, a 2,4-dianilino pyrimidine and related analogs demonstrated potent FAK kinase and cell activity and that these molecules have potential for further lead optimization (2005 AACR NCI EORTC, Philadelphia, PA). Chemistry efforts reported herein focused on increasing analog selectivity for FAK and improving ADME while maintaining or improving potency. SAR efforts focused on the C-2 indole, C-4 linker, C-4 aryl ring coupled with replacement of the aryl ring with heteroaryl rings combined with additional functional group(s) and the C-5 position. At the pyrimidine C-2 position, the indole was replaced with other heteroaromatic rings that were additionally substituted with groups to improve binding interactions with the Arg and Glu at the periphery of the ATP pocket. At the C-4 position, the 2-amino pyridine was replaced with different anilines, heteroaryl amines, aryl/heteroaryl methylamines and aryl/heteroaryl 2-phenyl ethylamines. Additional functional group(s) on the aryl/heteroaryl ring further optimized inhibitor binding interactions with FAK in the ribose phosphate binding region in the ATP pocket. Detailed SAR studies allowed us to obtain >100 fold selectivity for FAK over other structurally related kinases including PYK-2 as well as all other kinases with closely related sequence homology. The pyrimidine C-5 position interacts with a flexible lipophilic pocket. We undertook SAR studies at C-5 to determine the impact of replacing the bromine of PF-941222 with other groups. A seemingly minor modification to the C-5 position had a pronounced effect on kinase activity. In summary, detailed SAR studies were executed at the pyrimidine C-2, C-4 and C-5 positions of PF-941222. Taking all the SAR together, novel analogs have been produced that are potent inhibitors of FAK [kinase (1–10 nM), cell (10–100 nM)] and are >100X selective against other related kinases. A number of these potent and selective inhibitors have been co-crystallized with FAK. Subsets of these analogs demonstrated excellent  in vitro  selectivity against all CYPs screened with a low susceptibility to microsome and hepatocyte clearance and are suitable for further  in vitro  and  in vivo  evaluation. Design, synthesis, inhibitor kinase and cell activity, kinase selectivity profile, ADME as well as inhibitor chemical structure and inhibitor-FAK co-crystal structure data will be presented.