Intratumoral electroporation of plasmid encoded IL-12 and membrane-anchored anti-CD3 increases systemic tumor immunity.

Intratumoral delivery of plasmid IL 12 via electroporation (IT tavo EP) induces localized expression of IL 12 leading to regression of treated and distant tumors with durable responses and minimal toxicity. A key driver in amplifying this local therapy into a systemic response is the magnitude and composition of immune infiltrate in the treated tumor. While intratumoral IL 12 typically increases the density of CD3+ tumor infiltrating lymphocytes (TIL), this infiltrate is composed of a broad range of T cell subsets, including activated tumor specific T cells, less functional bystander T cells, as well as suppressive T regulatory cells. To encourage a more favorable on treatment tumor microenvironment, we explored combining this IL 12 therapy with an intratumoral polyclonal T cell stimulator membrane anchored anti CD3 to productively engage a diverse subset of lymphocytes including the non reactive and suppressive T cells. This study highlighted that combined intratumoral electroporation of IL 12 and membrane anchored anti CD3 plasmids can enhance cytokine production, T cell cytotoxicity, and proliferation while limiting the suppressive capacity within the TME. These collective anti tumor effects not only improve regression of treated tumors but drive systemic immunity with control of non treated contralateral tumors in vivo. Moreover, combination of IL 12 and anti CD3 restored the function of TIL isolated from a melanoma patient actively progressing on PD 1 checkpoint inhibitor therapy. This DNA encodable polyclonal T cell stimulator (membrane anchored anti CD3 plasmid) may represent a key addition to intratumoral IL-12 therapies in the clinic.