Abstract B028: Tipifarnib synergizes with axitinib in renal cell carcinoma models

Abstract

Abstract Clear cell renal cell carcinoma (ccRCC) is a highly vascularized tumor type, primarily due to loss of the Von Hippel-Lindau (VHL) gene that stabilizes hypoxia-inducible factor alpha proteins (HIF1α and HIF2a), primary drivers of the angiogenic response in this cell type. This includes production of angiogenic factors, such as VEGFA, which promotes the formation of blood vessels that provide tumors oxygen, nutrients, and growth factors. Anti-angiogenic tyrosine kinase inhibitors (TKIs) such as the VEGFR1/2/3 inhibitor axitinib have demonstrated therapeutic benefit in RCC patients by exploiting the critical dependency of RCC tumors on their vasculature. However, resistance to TKIs is commonly observed, leading to clinical relapse. Here, we report that the farnesyltransferase inhibitor (FTI), tipifarnib synergizes with axitinib, resulting in tumor regressions in the VHL-mutant RCC cell line-derived xenograft (CDX) models, 786-O and A498, and stasis in VHL-wild type Caki1 CDX and KI-9310 PDX models, despite the modest antitumor activity of either drug as monotherapy. To investigate the mechanism underlying this synergism, we performed immunohistochemical analysis of angiogenic markers in 786-O tumors treated with tipifarnib, axitinib, or the combination. Consistent with its mechanism of action, axitinib alone decreased angiogenesis compared to vehicle, which was evident as reduced expression of endothelial cell (EC) markers in the tumors. The combination of tipifarnib and axitinib, however, led to a further two-fold reduction in EC staining, suggesting that tipifarnib is enhancing the anti-angiogenic effect of axitinib. Further in vitro and in vivo studies are underway to establish the scope and mechanistic underpinnings of the axitinib-tipifarnib effects in RCC. Citation Format: Jovylyn Gatchalian, Linda Kessler, Hetika Vora Patel, Stacia Chan, Francis Burrows, Shivani Malik. Tipifarnib synergizes with axitinib in renal cell carcinoma models [abstract]. In: Proceedings of the AACR Special Conference: Advances in Kidney Cancer Research; 2023 Jun 24-27; Austin, Texas. Philadelphia (PA): AACR; Cancer Res 2023;83(16 Suppl):Abstract nr B028.