Abstract 3262: Effects of lenvatinib mesilate in combination with everolimus on VEGF and FGF-driven angiogenesis and tumor growth

Lenvatinib mesilate (lenvatinib) is an orally available inhibitor for multiple receptor tyrosine kinases (RTKs) that selectively inhibits the kinase activities of VEGFR1, 2, and 3, in addition to other proangiogenic and oncogenic pathway-related RTKs including FGFR1, 2, 3, and 4; PDGFRα; KIT; and RET. Recently, lenvatinib in combination with everolimus has shown longer progression free survival compared to lenvatinib or everolimus alone in renal cell carcinoma in a Phase 2 study. In this study, we evaluated the effect of lenvatinib in combination with everolimus on VEGF and bFGF-driven angiogenesis to elucidate the mechanism of combination action in preclinical models. Preclinical studies provide a plausible biologic rationale for the significant clinical benefit observed in RCC with the combination of lenvatinib and everolimus. Effects of lenvatinib, everolimus, and its combination on VEGF or bFGF activated intracellular signaling were analyzed in HUVEC by western blotting. Combination effects of lenvatinib and everolimus on VEGF and bFGF-induced proliferation or tube formation of HUVEC were examined using combination indexes (CI). Antitumor activities were tested in the KP-1/VEGF or KP-1/FGF models, where VEGF or FGF-induced tumor angiogenesis and tumor growth were enhanced in nude mice due to overexpressed VEGF or FGF in human pancreatic cancer KP-1 cells. Lenvatinib inhibited the VEGF or bFGF-driven phosphorylation of Erk1/2 (Thr202/Tyr204), S6K (Thr389), and S6K (Thr421/Ser424), and S6 (Ser235/Ser236), indicating the inhibition of both the MAPK pathway and the mTOR-S6K-S6 pathway. Everolimus inhibited the phosphorylation of S6K (Thr389), S6K (Thr421/Ser424), and S6 (Ser235/Ser236), but not Erk1/2. The combination showed greater inhibition for the phosphorylation of S6K (Thr421/Ser424) and S6 (Ser235/Ser236) than each single agent. Inhibitory activity of the combination at several molar ratios was mostly additive for VEGF-driven proliferation (CI: 0.799-1.167) and mostly synergistic for bFGF-driven tube formation (CI: 0.469-0.741). In the KP-1/VEGF or KP-1/FGF xenogtaft models, lenvatinib, everolimus, and the combination (p.o., qd x 14) significantly inhibited tumor growth compared to vehicle. In addition the combination of lenvatinib (7.5 mg/kg) and everolimus (15 mg/kg) showed significantly greater antitumor activity than higher dose of either lenvatinib (10 mg/kg) or everolimus (30 mg/kg) monotherapy. These results demonstrated enhancement of the in