Abstract 5017: MEDI1191, a novel IL-12 mRNA therapy for intratumoral injection to promote TH1 transformation of the patient tumor microenvironment

Patients who respond to PD-L1 / PD-1 immune checkpoint blockade tend to have an inflamed, TH1 polarised tumor microenvironment (TME), characterised by expression of interferon-γ (IFNγ) and PD-L1. Novel therapies that induce TH1 transformation of the patient TME therefore have the potential to enhance anti-tumor immunity. As a central mediator of TH1 immune responses, interleukin 12 (IL-12) directly induces IFNγ release from activated NK, NKT and T cells, and is known to play a key role in driving anti-tumor responses. However systemic recombinant IL-12 was poorly tolerated in early clinical trials. We therefore designed MEDI1191 as a novel IL-12-based therapy designed for injection directly into tumors, composed of a lipid nanoparticle (LNP)-formulated mRNA encoding human IL-12. We previously reported that intratumoral (IT) mouse (m) IL-12 mRNA, the surrogate for MEDI1191, promotes cytotoxic T cell-dependent anti-tumor immunity and enhances responses to PD-L1 blockade in pre-clinical models. Here, we demonstrate that IFNγ is also required for the anti-tumor activity of mIL-12 mRNA. A single dose of mIL-12 mRNA significantly increased expression of IFNγ and TH1 genes in MC38 tumor-bearing mice. Treatment with an IFNγ neutralising antibody blocked mIL-12 mRNA anti-tumor activity in this model. In addition, we report here that MC38 tumor rejection in response mIL-12 mRNA / anti-PD-L1 combination therapy correlates with increased cytotoxic T cell infiltration into tumors, and expansion of tumor-reactive T cells in the periphery. We next investigated the pharmocodynamic activity of MEDI1191 in patient tumor-derived models. A single IT dose of MEDI1191 induced human IL-12p70 expression in mice bearing four different patient-derived xenograft tumors. Furthermore, in an ex vivo patient tumor slice culture assay, MEDI1191 induced dose-dependent IL-12 release, IFNγ expression and upregulation of TH1-signature gene expression. IL-12 protein secretion was induced in slices of all patient tumors tested. However, the magnitude of the IFNγ response to MEDI1191 varied between patient tumors. Quantification of the tumoral T cell and NK cell numbers within the patient tumor samples revealed a positive correlation between MEDI1191-induced IFNγ release and baseline tumor NK infiltrate. These preclinical data demonstrate the potential for MEDI1191 to induce IFNγ-dependent TH1 transformation of the TME, and support the development of MEDI1191 as a potential treatment for patients with solid tumors, alone and in combination with inhibitors of the PD-1/PD-L1 T cell checkpoint. Citation Format: Nadia Luheshi, Susannah Hewitt, Fabien Garcon, Shannon Burke, Amanda Watkins, Kristen Arnold, John Zielinski, Philip Martin, Michael Sulikowski, Christopher Bagnall, Jean-Martin Lapointe, Gordon Moody, Han Si, Christopher Morehouse, Robert W. Wilkinson, Ronald Herbst, Joshua Frederick. MEDI1191, a novel IL-12 mRNA therapy for intratumoral injection to promote TH1 transformation of the patient tumor microenvironment [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 5017.