Development and Characterization of Selective FAK Inhibitors and PROTACs with In Vivo Activity.

Focal adhesion kinase (FAK) is an attractive drug target due to its overexpression in cancer. FAK functions as a non-receptor tyrosine kinase and scaffolding protein, coordinating several downstream signaling effectors and cellular processes. While drug discovery efforts have largely focused on targeting FAK kinase activity, FAK inhibitors have failed to show efficacy as single agents in clinical trials. Here, using structure-guided design, we report the development of a selective FAK inhibitor (BSJ-04-175) and degrader (BSJ-04-146) to evaluate the consequences and advantages of abolishing all FAK activity in cancer models. BSJ-04-146 achieves rapid and potent FAK degradation with high proteome-wide specificity in cancer cells and induces durable degradation in mice. Compared to kinase inhibition, targeted degradation of FAK exhibits pronounced improved activity on downstream signaling and cancer cell viability and migration. Together, BSJ-04-175 and BSJ-04-146 are valuable chemical tools to dissect the specific consequences of targeting FAK through small-molecule inhibition or degradation.

Discovery of a Pyrimidothiazolodiazepinone as a Potent and Selective Focal Adhesion Kinase (FAK) Inhibitor.

Focal adhesion kinase (FAK) is a tyrosine kinase with prominent roles in protein scaffolding, migration, angiogenesis, and anchorage-independent cell survival and is an attractive target for the development of cancer therapeutics. However, current FAK inhibitors display dual kinase inhibition and/or significant activity on several kinases. Although multitargeted activity is at times therapeutically advantageous, such behavior can also lead to toxicity and confound chemical-biology studies. We report a novel series of small molecules based on a tricyclic pyrimidothiazolodiazepinone core that displays both high potency and selectivity for FAK. Structure-activity relationship (SAR) studies explored modifications to the thiazole, diazepinone, and aniline "tail," which identified lead compound BJG-03-025. BJG-03-025 displays potent biochemical FAK inhibition (IC50 = 20 nM), excellent kinome selectivity, activity in 3D-culture breast and gastric cancer models, and favorable pharmacokinetic properties in mice. BJG-03-025 is a valuable chemical probe for evaluation of FAK-dependent biology.

Rapid and direct control of target protein levels with VHL-recruiting dTAG molecules.

Chemical biology strategies for directly perturbing protein homeostasis including the degradation tag (dTAG) system provide temporal advantages over genetic approaches and improved selectivity over small molecule inhibitors. We describe dTAGV-1, an exclusively selective VHL-recruiting dTAG molecule, to rapidly degrade FKBP12F36V-tagged proteins. dTAGV-1 overcomes a limitation of previously reported CRBN-recruiting dTAG molecules to degrade recalcitrant oncogenes, supports combination degrader studies and facilitates investigations of protein function in cells and mice.

Identification of a potent and selective covalent Pin1 inhibitor.

Peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (Pin1) is commonly overexpressed in human cancers, including pancreatic ductal adenocarcinoma (PDAC). While Pin1 is dispensable for viability in mice, it is required for activated Ras to induce tumorigenesis, suggesting a role for Pin1 inhibitors in Ras-driven tumors, such as PDAC. We report the development of rationally designed peptide inhibitors that covalently target Cys113, a highly conserved cysteine located in the Pin1 active site. The inhibitors were iteratively optimized for potency, selectivity and cell permeability to give BJP-06-005-3, a versatile tool compound with which to probe Pin1 biology and interrogate its role in cancer. In parallel to inhibitor development, we employed genetic and chemical-genetic strategies to assess the consequences of Pin1 loss in human PDAC cell lines. We demonstrate that Pin1 cooperates with mutant KRAS to promote transformation in PDAC, and that Pin1 inhibition impairs cell viability over time in PDAC cell lines.