Abstract PO047: AVB-500, a receptor tyrosine kinase AXL inhibitor, improves response to olaparib in uterine serous cancer

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Abstract Objectives: We determined whether inhibition of GAS6/AXL with AVB-500 in combination with olaparib could improve response in HR-proficient (HRP) uterine serous cancer (USC). Methods: Two USC cell lines (ARK1 & ARK4) were radiated with 10Gy, and RAD51 foci were identified by immunofluorescence (IF). These were treated with AVB-500 (Aravive Biologics, Houston, TX) in combination with the poly ADP ribose polymerase (PARP) inhibitor, olaparib. Colony forming assays were assessed after 4 days of treatment with either AVB-500 alone, olaparib alone or combination treatment (olaparib + AVB-500). Colonies were stained and absorbance was obtained to calculate relative cell survival using Graph Pad Prism. In vivo studies were performed using NOD-SCID mice injected with 1 × 107 ARK1 cells intraperitoneally followed by treatment q3 days for 14-day treatment period. Treatment groups were vehicle control, AVB-500 alone, olaparib alone and olaparib with AVB-500. Results: ARK1 and ARK4 cells were found to have an increase in gamma-H2AX and RAD51 foci after radiation that was consistent with HRP. In clonogenic assays, colonies were stained and absorbance was obtained for each experimental arm. Olaparib + AVB-500 had significantly less absorbance than the olaparib only group for ARK1s (0.417nm vs 0.756nm, p=0.001) as well as in ARK4s (0.186nm vs 0.641nm, p=0.003). In an intraperitoneal model with ARK1 tumors, the olaparib + AVB-500 treated group had less tumor weight than those treated with olaparib alone (0.008g vs 0.138g, p=0.002) and AVB-500 alone (0.008g vs 0.145g, p=0.0006) after a 14-day treatment period. Conclusions: AVB-500 in combination with olaparib demonstrates an improved response than olaparib alone with a greater decrease in tumor burden. This was demonstrated in two HRP cell lines. Additional therapeutic and mechanistic experiments are ongoing. Citation Format: Michael D. Toboni, Mary Mullen, Jo'an Tankou, Hollie Noia, Alyssa Oplt, Daniel Wilke, Dineo Khabele, Lindsay Kuroki, Andrea Hagemann, Carolyn McCourt, Premal Thaker, David Mutch, Matthew Powell, Katherine Fuh. AVB-500, a receptor tyrosine kinase AXL inhibitor, improves response to olaparib in uterine serous cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference: Endometrial Cancer: New Biology Driving Research and Treatment; 2020 Nov 9-10. Philadelphia (PA): AACR; Clin Cancer Res 2021;27(3_Suppl):Abstract nr PO047.