Abstract 2506: Preclinical characterization of LV305, a lentiviral vector targeting tumors expressing NY-ESO-1

Abstract The cancer-testis antigen, NY-ESO-1, is an attractive tumor antigen target for cancer immunotherapy, because it is expressed in numerous cancer types (e.g., melanoma, breast cancer, sarcoma, lung cancer) but not in normal adult tissues except the testis or placenta. Although recent studies using various NY-ESO-1 formulations show promising results, an optimal immunotherapeutic strategy to generate T cell responses for controlling tumor growth is still lacking. Lentiviral vectors (LVs) are proven tools for delivering nucleic acid payloads into cells due to their ability to transduce not only dividing cells but also quiescent cells, such as dendritic cells (DCs). Because DCs are essential for the initiation of T cell responses, we have engineered LV305 (a product candidate from ZVex™, our LV-based discovery platform) to selectively deliver the antigen-encoding NY-ESO-1 gene to human DCs in vivo. To develop tools to evaluate LV305 in a preclinical setting, we 1) generated a cell line, CIN.23, which is a CT26 murine colon cancer cell line that stably expresses human NY-ESO-1 protein; and 2) mapped and confirmed NY-ESO-1 CD8 and CD4 T cell epitopes recognized by H2d. Mice immunized with LV305 developed strong, dose-dependent, poly-functional, and cytotoxic NY-ESO-1-specific CD8 T cells within 14 days post-immunization and could be boosted with LV305 at least three times to recall peak-level CD8 T cell responses. Immunization with LV305 protected mice against CIN.23 tumor challenge, which was abrogated upon depletion of CD8 T cells. Adoptive transfer of CD8 T cells, together with CD4 T cells or NK cells, from LV305-immunized donor mice to tumor-bearing mice conferred significant protection against metastatic tumor growth. This protection was not observed when CD8 T cells alone were adoptively transferred. Taken together, these findings suggest that CD8 T cells are required but not sufficient for mediating LV305-induced anti-tumor efficacy. We have demonstrated the anti-tumor therapeutic potential of LV305-mediated in vivo DC immunization in murine models and are currently investigating LV305 in a phase I clinical trial in cancer patients with tumors expressing NY-ESO-1. Citation Format: Tina C. Albershardt, David J. Campbell, Andrea J. Parsons, Jan H. ter Meulen, Peter Berglund. Preclinical characterization of LV305, a lentiviral vector targeting tumors expressing NY-ESO-1. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2506. doi:10.1158/1538-7445.AM2015-2506