Abstract 2715: Utilizing a pH sensitive peptide (pHLIP) for tumor targeted delivery of an immunogenic peptide motif

Abstract Chimeric antigen receptor (CAR) T cell and immune-cell therapies are revolutionizing how patients are treated in the clinic by targeting tumor-specific antigens. Specifically, advances in antigen targeting of CD20 and CD19 with CAR T cell therapy has increased overall survival of this patient population and has influenced to expand T cell repertoire to novel antigen targets. However, limitations to these cell-based therapies are the lack of development against solid tumor antigens, partly due to the paucity of antigen candidates that are sufficiently specific to epithelial cancers. Therefore, technologies that can mark tumor cells for immune recognition could prove beneficial in the treatment of these solid cancers. This project aims to artificially deliver an antigen to tumor cells by harnessing a universal property of tumors: acidic microenvironment. The pH low insertion peptide (pHLIP) is a technology that targets solid tumors based on the low pH produced by the Warburg effect. pHLIP-conjugates have undergone extensive development for drug delivery, with one notable candidate CBX12 entering phase I clinical trials in 2021. Our system uses a pHLIP-conjugated SIINFEKL peptide (derived from ovalbumin) to serve as our model antigen system, with SIINFEKL-targeting T cells (OT1) that can be used as a tool to investigate antigen delivery, recognition, and functionality. We have observed through immunofluorescence that B16 F10 mouse melanoma cells treated in vitro with the 1uM pHLIP-SIINFEKL construct under acidic conditions can recruit OT1 cells and induce a T cell synapse. Preliminary in vivo experiments in C57BL/6-Tg OT1 mice bearing B16 F10 flank tumors showed that treatment with pHLIP-SIINFEKL by intravenous administration led to a suppression of tumor growth compared to controls, with approximately 50% smaller fold change in tumor volume. Cumulatively, these initial results suggest that pHLIP-SIINFEKL can be delivered to tumors to recruit OT1 cells to engage in antigen recognition and lead to efficacy in tumor growth delay in vivo. This technology has the capability to provide a novel approach to decorate solid tumors with engineered antigens for enhanced immune recognition and anti-tumor efficacy. Citation Format: Annali M. Yurkevicz, Yanfeng Liu, Peter M. Glazer. Utilizing a pH sensitive peptide (pHLIP) for tumor targeted delivery of an immunogenic peptide motif [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2715.