Abstract 4287: Talimogene laherparepvec activates systemic T-cell-mediated anti-tumor immunity

Abstract

Abstract Talimogene laherparepvec is an investigational oncolytic immunotherapy based on a modified herpes simplex virus type-1 (HSV-1) immunotherapy designed to selectively replicate in tumors and to initiate an anti-tumor immune response. Intralesional administration of talimogene laherparepvec is intended to result in oncolysis within injected tumors. Iterative replication of virus within permissive tumor tissue results in lytic cell destruction and local release of progeny virus and tumor derived antigens. GM-CSF, a product of the viral transgene, is also produced locally such that it can recruit and stimulate antigen presenting cells which, in addition to relevant tumor-derived antigens, are required for the initiation of a systemic antitumor immune response. The talimogene laherparepvec-induced immune mediated mechanism of action in both the virus-injected and distant tumors have yet to be fully understood therefore, we evaluated viral replication, tumor cell lysis, and the changes in immune cell populations in both the injected and distant tumors using syngeneic contralateral tumor models. Animals received a single intratumoral dose of the murine surrogate of talimogene laherparepvec (OncoVEXmuGM-CSF), which induced regression in the majority of virus-injected tumors and tumor growth inhibition/regression in the contralateral (uninjected) tumors. HSV-1 antigen was only detected by IHC in the virus-injected tumor and not the contralateral tumor (and no other tissues). Virally-mediated tumor destruction (oncolysis) was also localized to only the virus-injected tumor. In preliminary experiments, morphometric analysis of the tumor tissue revealed that the percent area of CD3+ and CD8+ lymphocytes were significantly increased in both the virus-injected and contralateral tumors compared to the formulation control mice. In addition, the percent area occupied by CD103+ cells (a marker found on potent cytotoxic T cell stimulating dendritic cells) was increased in the virus-injected tumor compared to the contralateral tumor and the tumors in the control animals. Although cellular infiltration was increased in both virus-injected and contralateral tumors and was inversely correlated with tumor volume, the decreased volume of injected tumors was attributed to viral oncolysis. Taken together these data supports that talimogene laheparepvec activates a systemic T cell mediated anti-tumor immune response. Citation Format: Julia Piasecki, Jim Rottman, Tiep Le, Rafael Ponce, Courtney Beers. Talimogene laherparepvec activates systemic T-cell-mediated anti-tumor immunity. [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 4287. doi:10.1158/1538-7445.AM2015-4287