Defactinib

Defactinib is a novel FAK inhibitor, which inhibits FAK phosphorylation at the Tyr397 site in a time- and dose-dependent manner.

In Vitro:VS-6063 inhibits FAK phosphorylation at the Tyr397 site in a time- and dose-dependent manner. The combination of VS-6063 and Paclitaxel markedly decreases proliferation and increases apoptosis, which results in 92.7% to 97.9% reductions in tumor weight. RPPA data shows that VS-6063 reduces levels of AKT and YB-1 in taxane-resistant cell lines. The expression of pFAK (Tyr397) is statistically significantly inhibited by VS-6063 in a dose-dependent manner in all cell lines. VS-6063 inhibits pFAK (Tyr397) expression within 3 hours, with a gradual return of expression by 48 hours[1].

In Vivo:VS-6063 doses of 25 mg/kg twice a day or greater statistically significantly inhibits pFAK (Tyr397) at 3 hours, with return of expression noted by 24 hours. Therefore, administration of VS-6063 at 25 mg/kg twice a day is selected as the dosing schedule for subsequent therapy experiments. For therapy experiments, female nude mice bearing HeyA8 tumors in the peritoneal cavity are randomly divided into 4 groups (n=10 per group): 1) vehicle orally twice daily and phosphate-buffered saline intraperitoneally weekly (control); 2) VS-6063 25 mg/kg orally twice daily; 3) PTX intraperitoneally weekly; and 4) both VS-6063 25 mg/kg orally twice daily and PTX intraperitoneally weekly. There is an 87.4% reduction in tumor weight by PTX monotherapy in the HeyA8 model, and combination therapy resulted in the greatest tumor weight reduction, with a 97.9% reduction (P=0.05 compared with PTX). In the SKOV3ip1 model, a 92.7% tumor weight reduction is observed in the combination group compared with PTX (P<0.001)[1].

References:
[1]. Kang Y, et al. Role of focal adhesion kinase in regulating YB-1-mediated paclitaxel resistance in ovarian cancer. J Natl Cancer Inst. 2013 Oct 2;105(19):1485-95.

Maintenance Defactinib Versus Placebo After First-Line Chemotherapy in Patients With Merlin-Stratified Pleural Mesothelioma: COMMAND-A Double-Blind, Randomized, Phase II Study.[Pubmed:30785827]

J Clin Oncol. 2019 Apr 1;37(10):790-798.

PURPOSE: Inhibition of focal adhesion kinase has been shown to selectively kill mesothelioma cells that express low levels of moesin-ezrin-radixin-like protein (merlin). On this basis, we designed a randomized, phase II trial to investigate whether Defactinib as maintenance therapy after standard first-line chemotherapy could improve progression-free survival (PFS) in patients with malignant pleural mesothelioma (MPM). METHODS: This global, double-blind, randomized, placebo-controlled trial was conducted in patients with advanced MPM and disease control after at least four cycles of first-line chemotherapy. Patients were stratified for merlin and then randomly assigned (in a 1:1 fashion) to receive either oral Defactinib or placebo until disease progression, unacceptable toxicity, or withdrawal occurred. The coprimary end points were PFS and overall survival (OS). Quality of life (QoL) was assessed using the Lung Cancer Symptom Scale for Mesothelioma tool. RESULTS: Three hundred forty-four patients were randomly assigned to receive either Defactinib (n = 173) or placebo (n = 171). The median PFS was 4.1 months (95% CI, 2.9 to 5.6 months) for Defactinib versus 4.0 months (95% CI, 2.9 to 4.2 months) for placebo. The median OS was 12.7 months (95% CI, 9.1 to 21 months) for Defactinib versus 13.6 months (95% CI, 9.6 to 21.2 months) for placebo (hazard ratio, 1.0; 95% CI, 0.7 to 1.4). Although shorter survival for both Defactinib- and placebo-treated patients was observed, in the patients who had merlin-low MPM compared with the patients who had merlin-high MPM, there were no statistical differences in response rate, PFS, OS, or QoL between the treatment groups. The most common grade 3 or worse adverse events were nausea, diarrhea, fatigue, dyspnea, and decreased appetite. CONCLUSION: Neither PFS nor OS was improved by Defactinib after first-line chemotherapy in patients with merlin-low MPM. Defactinib cannot be recommended as maintenance therapy for advanced MPM.

LC-ESI-MS/MS determination of defactinib, a novel FAK inhibitor in mice plasma and its application to a pharmacokinetic study in mice.[Pubmed:29145097]

J Pharm Biomed Anal. 2018 Feb 5;149:358-364.

A sensitive, specific, selective and rapid LC-ESI-MS/MS method has been developed and validated for the quantification of Defactinib in mice plasma using (13)C3,(15)N-tofacitinib as an internal standard (I.S.). Sample preparation was accomplished through a liquid-liquid extraction process. Baseline chromatographic resolution of Defactinib and the I.S. was achieved on an Atlantis dC18 column using an isocratic mobile phase comprising 0.2% formic acid in water and acetonitrile (25:75, v/v) delivered at a flow rate of 0.5mL/min. Defactinib and the I.S. eluted at approximately 1.59 and 0.99min, respectively. The total chromatographic run time was 2.50min. A linear response function was established in the concentration range of 0.13-106 ng/mL. Method validation was performed as per regulatory guidelines and the results met the acceptance criteria. The intra- and inter-day accuracy and precision were in the range of 5.57-13.3 and 8.63-12.1%, respectively. Defactinib was found to be stable under various stability conditions. This novel method has been applied to a pharmacokinetic study in mice.