Longitudinal Monitoring Of Neoepitope-Specific T Cell Repertoires In Patient Blood Following Cancer Immunotherapy

Abstract T cells targeting neoepitopes derived from mutations exclusive to the tumor are one of the main drivers of cancer immunotherapy efficacy. Tracking these neoepitope-specific T cells during cancer immunotherapy has been hampered by the impracticality of repeated sampling from the tumor, and by the low frequency of neoepitope-specific T cells in peripheral blood. An ultra-sensitive and high-throughput technology (imPACT) has been developed for the identification and isolation of neoepitope-specific T cells from peripheral blood. Subjects with colorectal cancer, endometrial adenocarcinoma, nasopharyngeal carcinoma and other solid tumors were treated with AB122 (anti-PD-1 antibody) as part of an ongoing dose-escalation clinical trial. Pre-treatment blood samples were analyzed to identify the basal repertoire of neoepitope-specific T cells. Evolution of this repertoire during AB122 treatment was monitored to enable immune phenotyping and correlation with clinical outcomes. In addition, transcriptional profile changes were monitored at the single-cell level for each neoepitope-specific T cell. These data will enable us to analyze T cells targeting neoepitopes and identify driver mutations that correlate with and may be responsible for therapeutic benefit. More broadly, this platform technology promises to significantly advance our understanding of T cell-mediated mechanisms of cancer immunotherapy. Citation Format: Songming Peng, Benjamin Yuen, Joanne Tan, Fangfang Yin, Robert Bao, Zheng Pan, Olivier Dalmas, Duo An, Boi Quach, Michael Yi, Michael Bethune, Stefanie Mandl, Matt Walters, Juan Jaen, Alex Franzusoff. Longitudinal monitoring of neoepitope-specific T cell repertoires in patient blood following cancer immunotherapy [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 4042.