Discovery of potent focal adhesion kinase (FAK) inhibitor A8 with enhanced antitumor activity.

FAK has emerged as a promising therapeutic target for cancer treatment due to its role in tumor survival, metastasis, and invasion. Herein, we report the rational design, synthesis, and comprehensive evaluation of a novel FAK inhibitor, compound A8. Our structure-activity relationship (SAR) studies identified A8 as a potent FAK inhibitor, with an FAK-IC50 value of 0.87 nM, superior to VS6063 (1.49 nM). In vitro studies demonstrated that A8 significantly suppressed tumor cell viability, cancer stem cell activity, and cell migration in A549 and SKOV-3 cell lines. Mechanistic insights were provided by surface plasmon resonance (SPR) analysis, revealing high-affinity binding of A8 to FAK with a Kd value of 15 μM. Radiolabeling studies with [18F]A8 highlighted favorable tumor uptake and retention in S180 tumor-bearing mice. Notably, A8 efficiently penetrated the blood-brain barrier, with brain uptake values reaching 2.63 ± 0.63 %ID/g at 15 min and 1.62 ± 0.77 %ID/g at 120 min. In vivo antitumor efficacy trials in A549 and SKOV-3 tumor models confirmed A8's robust activity, with tumor inhibition rates of 59.15 % and 57.9 %, respectively, surpassing VS6063 and standard chemotherapeutics. Combination therapy with paclitaxel further enhanced A8's antitumor effects in SKOV-3 models. Acute toxicity studies indicated that A8 was well-tolerated up to 2000 mg/kg in mice, with no observed acute toxicity. Molecular docking and dynamics simulations substantiated the stable binding of A8 to the FAK protein. Collectively, our findings underscore the potential of compound A8 as a lead candidate for FAK-targeted cancer therapeutics, warranting further preclinical and clinical investigations.