Abstract 3264: Lenvatinib in combination with everolimus demonstrated enhanced antiangiogenesis and antitumor activity in human RCC xenograft models

Lenvatinib mesilate (lenvatinib) is an oral multiple receptor tyrosine kinase (RTK) inhibitor that selectively inhibits the kinase activities of vascular endothelial growth factor (VEGF) receptors VEGFR1 (FLT1), VEGFR2 (KDR), and VEGFR3 (FLT4), in addition to other proangiogenic and oncogenic pathway-related RTKs including fibroblast growth factor (FGF) receptors FGFR1, 2, 3, and 4; the platelet-derived growth factor (PDGF) receptor PDGFRα; KIT; and RET. Lenvatinib showed antitumor activity against various tumor types mainly through its potent inhibition of angiogenesis, and is currently marketed for the treatment of patients with radioactive iodine-refractory differentiated thyroid cancer. Recently, lenvatinib in combination with everolimus has shown longer progression free survival compared to lenvatinib or everolimus alone in renal cell carcinoma in Phase 2 study. The aim of this study is to elucidate the activity of the combination of lenvatinib and everolimus in preclinical human RCC xenograft models. We examined antitumor activity in two human RCC (A-498 and Caki-1) xenograft models orally treated with lenvatinib (10 mg/kg), everolimus (30 mg/kg), and the combination of lenvatinib and everolimus for 1 or 2 weeks. The antitumor proliferation and antiangiogenic effects were evaluated by immunohistochemistry (IHC) using anti Ki67 antibody and anti CD31 antibody, respectively. The induction of apoptosis was detected by TUNEL assay. To analyze the gene expression profile of tumor samples, microarray analysis were also conducted. The antitumor activity of the combination of lenvatinib and everolimus was greater than that of either agent administered alone in A-498 and Caki-1 xenograft models. The combination caused tumor regression and had no remarkable body weight loss. IHC analysis revealed decrease of microvessel density in lenvatinib and combination groups, and also decrease in the proportion of proliferative cells in everolimus treated and combination-treated group in A-498 model. In TUNEL assay, significant induction of apoptosis was observed only in the combination-treatment group. The analysis of gene expression profile in A-498 xenograft tumors also supported these results: lenvatinib alone upregulated hypoxia-related genes and everolimus decreased proliferation-related genes. The combination of these 2 drugs induced blends of the gene expression changes caused by each single treatment. Our results indicate that treatment of lenvatinib in combinat