Structure-based discovery of hydrocarbon-stapled paxillin peptides that block FAK scaffolding in cancer.

The focal adhesion kinase (FAK) scaffold provides FAK-targeted cancer therapeutics with greater efficacy and specificity than traditional kinase inhibitors. The FAK scaffold function largely involves the interaction between FAK's focal adhesion targeting (FAT) domain and paxillin, ultimately regulating many hallmarks of cancer. We report the design of paxillin LD-motif mimetics that successfully inhibit the FAT-paxillin interaction. Chemical and biochemical screening identifies stapled peptide 1907, a high affinity binder of the FAT four-helix bundle with ~100-fold greater binding affinity than the native LD2-sequence. The X-ray co-crystal structure of the FAT-1907 complex is solved. Myristoylated 1907-analog, peptide 2012, delocalizes FAK from focal adhesions, induces cancer cell apoptosis, reduces in vitro viability and invasion, and decreases tumor burden in B16F10 melanoma female mice. Enzymatic FAK inhibition produces no comparable effects. Herein, we describe a biologically potent therapeutic strategy to target the FAK-paxillin complex, a previously deemed undruggable protein-protein interaction.