Abstract 2242: Roles of FGFR inhibition on murine RCC cells in combination antitumor activity of lenvatinib with anti-PD1 antibody via regulatingIFN gamma signaling pathway
Authors: Adachi Yusuke , Ichikawa Kenji , Kato Yu , Funahashi Yasuhiro 
Published: August 2019

Abstract
Lenvatinib mesilate (LEN) 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. LEN plus everolimus for advanced renal cell carcinoma (RCC) after one prior anti-VEGF therapy was approved in the US and EU in 2016. Currently, Phase1b/2 clinical trial of LEN in combination with pembrolizumab with selected solid tumors including RCC and Phase3 study of LEN in combination with everolimus or pembrolizumab for metastatic RCC patients are in progress. In this study, we investigated the antitumor and immunomodulatory activities of LEN alone and in combination with anti-PD1 Ab and explored the mechanism of action underlying the activities of LEN and PD1 blockade in preclinical syngeneic RCC models.
We examined antitumor activity of combination treatment of LEN at 10 mg/kg (po, qd) and anti-PD1 Ab at 10 mg/kg (ip, twice weekly) in the murine subcutaneous RCC model using RAG cell line. Immune cell population analyses in tumor tissues were performed by flow cytometer. Immune-related gene expression profile in tumor tissues or cultured cells was analyzed by qPCR and RNA seq. Effects on FGFR and IFN gamma (IFNγ) signaling pathways and their downstream molecules in cultured cells were analyzed by western blot.
In the murine syngeneic RAG tumor model, the combination treatment of LEN and anti-PD1 Ab showed tumor shrinkage, and some of tumors were regressed to nonpalpable sizes with long duration of response. LEN alone and in combination with anti-PD1 Ab significantly decreased the population of tumor associated macrophage in tumor tissues by FCM analysis. Gene expression analysis for immune cell responses in tumor tissues revealed the upregulation of IFNγ and its downstream genes including PD-L1 with combination of LEN and anti-PD1 Ab. Western blot analysis elucidated that FGFR signaling pathway inhibited the activation of IFNγ signaling pathway and the induction of PD-L1 expression in murine RCC cells, and LEN-treatment reactivated the IFNγ signaling pathway by inhibition of FGFR signaling.
Combination of LEN and anti-PD1 Ab showed greater antitumor activity including tumor shrinkage with long duration of response in the murine RCC model. Modulation of immune microenvironment by LEN and combination of LEN with PD1 Ab may underlie the strong antitumor activity in preclinical RCC model. Inhibitory activity of LEN against FGFR reactivated the IFNγ pathway and PD-L1 expression suppressed by activation of FGFR signaling pathway, and this inhibitory activity of LEN may potentiate the antitumor activity of combination treatments with anti-PD1 Ab. These preclinical results provide one of the unique mechanisms of combinational effect of LEN with PD1 blockade in the preclinical RCC model.
Citation Format: Yusuke Adachi, Kenji Ichikawa, Yu Kato, Yasuhiro Funahashi. Roles of FGFR inhibition on murine RCC cells in combination antitumor activity of lenvatinib with anti-PD1 antibody via regulatingIFN gamma signaling pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2242.