In vitro activity: In taxane-sensitive (SKOV3ip1) and taxane-resistant (SKOV3-TR) cell lines, Defactinib significantly inhibits pFAK (Tyr397) expression. The combination of Defactinib and paclitaxel synergistically decreases proliferation and increases apoptosis in SKOV3ip1, SKOV3-TR, HeyA8 and HeyA8-MDR cells. The combination of Defactinib and Y15 synergistically decreases viability, clonogenicity, and cell attachment in thyroid cancer cell lines.

Kinase Assay: Defactinib inhibited FAK phosphorylation at the Tyr397 site in a time- and dose-dependent manner. The combination of Defactinib and paclitaxel markedly decreased proliferation and increased apoptosis, which resulted in 92.7% to 97.9% reductions in tumor weight. RPPA data showed that Defactinib reduced levels of AKT and YB-1 in taxane-resistant cell lines. FAK inhibition enhanced chemosensitivity in taxane-resistant cells by decreasing YB-1 phosphorylation and subsequently CD44 in an AKT-dependent manner. In human ovarian cancer samples, nuclear FAK expression was associated with increased nuclear YB-1 expression (χ2) = 37.7; P < .001). Coexpression of nuclear FAK and YB-1 was associated with statistically significantly worse median overall survival (24.9 vs 67.3 months; hazard ratio = 2.64; 95% confidence interval = 1.38 to 5.05; P = .006).

Cell Assay: Ovarian cancer cells are treated with increasing concentrations of Defactinib for 96 hours and then subjected to the MTT assay. Results are confirmed with triplicate experiments.