Abstract 12: Antitumor activity of lenvatinib in combination with everolimus or an anti-PD1 antibody in preclinical RCC models
Authors: Adachi Yusuke , Kimura Takayuki , Matsuki Masahiro , Matsui Junji , Funahashi Yasuhiro 
Published: August 2018

Abstract
Lenvatinib mesilate (lenvatinib) is an oral multiple receptor tyrosine kinase (RTK) inhibitor that selectively inhibits the kinase activities of VEGFR1-3, in addition to other proangiogenic and oncogenic pathway-related RTKs including FGFR1-4; PDGFRα; KIT; and RET. Lenvatinib plus everolimus for advanced renal cell carcinoma (RCC) after one prior anti-VEGF therapy was approved in the US and EU in 2016. Currently, Phase3 clinical study of lenvatinib in combination with everolimus or pembrolizumab for metastatic RCC patients is in progress. However, the detailed mechanisms underlying the efficacy of these combination treatments remain to be elucidated. In this study, we investigated the antitumor activities of lenvatinib in combination with everolimus or anti-PD1 mAb in preclinical RCC models. We examined antitumor activities in four human RCC (A-498, VMRC-RCW, Caki-1, and ACHN) xenograft models orally treated with lenvatinib, everolimus, and their combination. Expression of Ki67 and phosphorylation of S6 in RCC xenograft models were analyzed by immunofluorescence (IF) staining. Inhibitory effects of lenvatinib and everolimus on the phosphorylation of S6K (T389 and T421/S424), and S6 (S235/S236) were analyzed by western blot in vitro. We also examined antitumor activity of combination treatment of lenvatinib and anti-PD-1 mAb in RAG murine RCC model. The combination of lenvatinib with everolimus showed greater antitumor activity than that of either mono-treatment in all of 4 RCC xenograft models we examined and led to tumor regression in three out of 4 models (A-498, Caki-1, and ACHN). IF imaging showed expression of Ki67 was further suppressed with the combination treatment compared to lenvatinib and everolimus mono-treatments. Phospho-S6 (p-S6) signal were localized in perivascular regions of control group. Lenvatinib mono-treatment decreased p-S6 in the region apart from vessels, but some staining of p-S6 in perivascular regions were remained. The combination treatment further suppressed p-S6 staining regardless of the regions. In RAG syngeneic model, the combination treatment of lenvatinib at 10 mg/kg and anti-PD-1 mAb showed tumor shrinkage and tumors were regressed to nonpalpable sizes in 3 of 6 mice, although lenvatinib and anti-PD-1 mAb mono-treatments only slowed growths of RAG tumor. Our results indicate that combination of lenvatinib and everolimus enhances the inhibitory effects of mTOR signaling and tumor proliferation and showed greater antitumor activities. Combination of lenvatinib and anti-PD-1 mAb showed greater antitumor activity including tumor shrinkage, which was not demonstrated by each monotherapy in the murine RCC syngeneic model. These preclinical results provide one of the mechanisms of combinational effect of lenvatinib and everolimus, or PD-1 blockade in RCC.
Citation Format: Yusuke Adachi, Takayuki Kimura, Masahiro Matsuki, Junji Matsui, Yasuhiro Funahashi. Antitumor activity of lenvatinib in combination with everolimus or an anti-PD1 antibody in preclinical RCC models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 12.