Abstract 3457: Rebastinib, a TIE2 antagonist improves chemotherapy response in homologous recombination proficient epithelial ovarian cancer murine models
Authors: Gupta Vijayalaxmi G. , Roby Katherine F. , Pathak Harsh B. , Godwin Andrew K. , Gunewardena Sumedha , Khabele Dineo 
Published: June 2022

Abstract
Objectives: The Angiopoietin (ANGPT)/TIE2 kinase axis plays a critical role in cancer angiogenesis. Rebastinib, an investigational TIE2 inhibitor inhibits Tie2 receptor in endothelial cells and macrophages. M2-like Tie2+ macrophages, being pro-tumorigenic, are an attractive target for cancer therapy. Current clinical trials are testing rebastinib with chemotherapy in platinum-resistant ovarian cancer. However, the mechanism is not fully understood. The objective of this study was to determine the effects of rebastinib alone and combined with chemotherapy in preclinical models of ovarian cancer.
Methods: RNA-Seq was carried out to determine rebastinib-induced gene expression in ID8 cells and PMJ2R murine peritoneal macrophages. To determine the pharmacodynamics of immune cells in ascites, syngeneic ID8 mice were pre-treated with 10 mg/kg/day rebastinib/control for a week, followed by rebastinib with or without 20 mg/kg carboplatin + 12 mg/kg paclitaxel (chemo) for two weeks. Mice were sacrificed 24h after the last treatment to harvest ascites for flow cytometry. Cohorts of mice from syngeneic ID8 murine model and from a patient derived xenograft (PDX) model of ovarian cancer were used for survival analysis.
Results: RNA-Seq showed that in ID8 cells, 1528 genes were upregulated and 3115 genes were downregulated by rebastinib. In macrophages, 2302 genes were upregulated and 2970 genes were downregulated. Several ANGPT-like genes (ANGPTL2, ANGPTL4, ANGPTL6) involved in tumorigenesis, angiogenesis, proliferation were downregulated 2X-10X (p&lt;0.001) in ID8 cells and macrophages. ANGPTL1, an anti-angiogenic and anti-apoptotic gene, was increased 10X in ID8 cells (p&lt;0.001) but not altered in macrophages. ANGPT2, a context-dependent agonist/antagonist of TIE2 pathway, was increased 1.42X in ID8 (P&lt;0.05) cells and 4.6X in macrophages (p&lt;0.001). Flow studies showed that rebastinib significantly increased CD45+ macrophage (p&lt;0.03 vs. chemo; p&lt;0.02 vs. rebastinib+chemo), maintained Th leukocytes (p&lt;0.03, vs. chemo) and significantly increased cytotoxic T cells (p&lt;0.02 vs. control; p&lt;0.0004, p&lt;0.0001 vs. chemo and rebastinib+chemo, respectively). Rebastinib had no significant effect on regulatory T cells, Tie2+ macrophages or Tie2+ M2 macrophages. Rebastinib combined with chemotherapy improved median survival significantly in murine models of ovarian cancer - ID8 (p&lt;0.01) and PDX (p&lt;0.0001).
Conclusions: Rebastinib exerts differential effects on tumor cells and macrophages that could contribute to its mechanism of action. Rebastinib alters immune cells and increases cytotoxic T cells in ascites. Rebastinib combined with chemotherapy extends survival in PDX and syngeneic ID8 murine models of ovarian cancer. Further investigation using rational combinations of rebastinib and chemotherapy are underway.
Citation Format: Vijayalaxmi G. Gupta, Katherine F. Roby, Harsh B. Pathak, Andrew K. Godwin, Sumedha Gunewardena, Dineo Khabele. Rebastinib, a TIE2 antagonist improves chemotherapy response in homologous recombination proficient epithelial ovarian cancer murine models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3457.