Abstract 5549: Antitumor efficacy of the oncolytic peptide LTX-315 in genetic mouse models that resist conventional chemo- and immunotherapeutic treatments

Abstract

Abstract LTX-315 is an oncolytic peptide that induces immunogenic cancer cell death and is currently evaluated in phase 1 clinical trials for its ability to trigger recruitment of tumor-specific T cells to tumors. Previous experimental studies identified LTX-315's ability to control cancer in mice grafted with various tumor cell lines. Here we extend our analyses to conditional genetic mouse models of both melanoma (driven by Braf and Pten alterations) and soft tissue sarcoma (driven by Kras and P53 alterations). In these genetic models, cancer cells are derived from somatic cells that are transformed in their normal tissue microenvironment and progress to high-grade tumors that are poorly infiltrated by T cells and typically resist prescribed chemo- and immunotherapeutic treatments. We report that LTX-315 not only delays tumor progression substantially in both models, but also profoundly alters the tumor microenvironment, most notably characterized with CD8+ T cell, NK cell and dendritic cell infiltration. Transition from a ‘cold' to a ‘hot' tumor microenvironment was also observed in patients with melanoma, sarcoma and breast cancer. Furthermore, CD8+ T cell depletion in mice abrogated long-term antitumor efficacy of LTX-315, indicating that these cells are required for drug-induced tumor control. Importantly, the ability to convert non-T-cell-infiltrated tumors into ones that display antitumor T cell immunity opens the possibility to prime and make unresponsive tumors sensitive for systemic immune treatments. Citation Format: Mikael J. Pittet, Hsin-Wei Liao, Baldur Sveinbjørnsson, Øystein Rekdal. Antitumor efficacy of the oncolytic peptide LTX-315 in genetic mouse models that resist conventional chemo- and immunotherapeutic treatments [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5549.