ABSTRACT
PURPOSE: We investigated the combination of tivantinib, a c-MET tyrosine kinase inhibitor (TKI), and bevacizumab, an anti-VEGF-A antibody. METHODS: Patients with advanced solid tumors received bevacizumab (10 mg/kg intravenously every 2 weeks) and escalating doses of tivantinib (120-360 mg orally twice daily). In addition to safety and preliminary efficacy, we evaluated pharmacokinetics of tivantinib and its metabolites, as well as pharmacodynamic biomarkers in peripheral blood and skin. RESULTS: Eleven patients received the combination treatment, which was generally well tolerated. The main dose-limiting toxicity was grade 3 hypertension, which was observed in four patients. Other toxicities included lymphopenia and electrolyte disturbances. No exposure-toxicity relationship was observed for tivantinib or metabolites. No clinical responses were observed. Mean levels of the serum cytokine bFGF increased (p = 0.008) after the bevacizumab-only lead-in and decreased back to baseline (p = 0.047) after addition of tivantinib. Tivantinib reduced levels of both phospho-MET (7/11 patients) and tubulin (4/11 patients) in skin. CONCLUSIONS: The combination of tivantinib and bevacizumab produced toxicities that were largely consistent with the safety profiles of the individual drugs. The study was terminated prior to establishment of the recommended phase II dose (RP2D) due to concerns regarding the mechanism of tivantinib, as well as lack of clinical efficacy seen in this and other studies. Tivantinib reversed the upregulation of bFGF caused by bevacizumab, which has been considered a potential mechanism of resistance to therapies targeting the VEGF pathway. The findings from this study suggest that the mechanism of action of tivantinib in humans may involve inhibition of both c-MET and tubulin expression. TRIAL REGISTRATION: NCT01749384 (First posted 12/13/2012).
