Abstract 629: Delivering type I interferon to dendritic cells empowers tumor eradication and immune combination treatments

Abstract An ideal generic cancer immunotherapy should mobilize the immune system to destroy tumor cells without harming healthy cells and remain active in case of recurrence. Furthermore, it should preferably not rely on tumor-specific surface markers, as these are only available in a limited set of malignancies. Despite approval for treatment of various cancers, clinical application of cytokines is still impeded by their multiple toxic side effects. Type I interferon (IFN), for instance, has a long history in the treatment of cancer, but its multifaceted activity pattern and complex side effects prevent its optimal clinical use. Here we develop AcTakines (Activity-on-Target cytokines), optimized (mutated) immunocytokines that are up to 1000-fold more potent on target cells, allowing specific signaling in selected cell types only. As conventional Dendritic Cells (cDC) are essential for IFN antitumor efficacy, we targeted type I IFN-derived “AcTaferon (AFN)” to Clec9A+ cDC. Clec9A-AFN therapy displayed strong antitumor activity in murine melanoma (B16), breast carcinoma (4T1) and lymphoma models (A20), as well as against human RL lymphoma in immunodeficient NSG mice reconstituted with a human immune system. In sharp contrast to wild-type IFN therapy, the antitumor efficacy of Clec9A-AFN was not accompanied by any detectable toxicity, assessed by body weight and several hematological parameters. Clec9A-AFN effects were lost in CD8-depleted or Batf3-/- mice, and depended on IFN signaling in cDCs but not in T lymphocytes. Combined with α-PDL1 immune checkpoint blockade, Treg-depleting anti-CTLA4 + anti-OX40 therapy, immunogenic chemotherapy, or low-dose TNF, complete tumor regressions and long-lasting tumor immunity (memory) were obtained, still without any adverse effects. Our findings thus indicate that DC-targeted AFN provides a highly efficient, off-the-shelf and safe cancer immunotherapy, with possible application in a broad range of malignancies. Citation Format: Jan H. Tavernier, Anje Cauwels, Sandra Van Lint, Franciane Paul, Geneviève Garcin, Alexander Van Parys, Nikolai Kley, Gilles Uzé. Delivering type I interferon to dendritic cells empowers tumor eradication and immune combination 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 629.