Antibody-TLR3 agonist-conjugates for immunotherapy of tumors

In most cancers, immunosuppressive tumor-associated macrophages (TAMs) restrains immunotherapy. Induction of immunogenic cell death in tumor cells and simultaneously programming M2 TAMs to pro-inflammatory M1 TAMs employing dsRNA agonists for Toll-like receptor 3 (TLR3) represents an appealing in situ immunomodulation strategy. Here we describe an exceptional therapeutically effect of systemically delivered antibody-TLR3 agonist conjugates for targeting epidermal growth factor variant III (EGFRvIII) on tumor cells. We show in the SMAvIII tumor model that monotherapy with picomolar amounts of RICIA induces regression of tumors leading to increase in survival time and results in complete tumor clearance in a significant fraction of mice when compared to treatment with TLR3 agonist conjugated with an unspecific control antibody. Mechanistically, targeted delivery of TLR3 agonist reshapes the immunosuppressive tumor environment by mimicking viral infection leading to increased expression of the interferon beta (IFN-β) gene (Ifnb1), by subsequent induction of an inflammatory state characterized by RNA-expression signatures indicating induction of apoptosis, interleukin 1beta (IL-1β) signaling, and programming of immunosuppressive M2 TAMs to activated pro-inflammatory M1 TAMs. Thus, we show that targeted activation of TLR3 represents a promising therapeutic strategy for immune-modulation of tumors with the prospect to elicit anti-tumor immune responses.