Immunogenic tumor cell death and T-cell-derived IFN-γ elicit tumoricidal macrophages to potentiate OX40 immunotherapy.

Understanding the mechanisms limiting OX40 agonist antibody efficacy is critical for developing more effective combination immunotherapies. Tumor microenvironment (TME) analysis revealed that OX40-antibody-responsive mice harbored tumor-associated macrophages (TAMs) with elevated NOS2 expression and heightened pattern recognition receptor (PRR) activation and interferon gamma (IFN-γ) signaling. In addition, patients with more favorable treatment responses to OX40 antibody therapy exhibited increased NOS2 expression. Mechanistically, tumor-infiltrating T-cell-derived IFN-γ synergizes with endogenous ligands of PRR released during immunogenic cell death to drive NOS2+ TAMs reprogramming. Translating these insights into therapeutic strategy, a Combo approach composing of MPLA, IFN-γ, and OX40 agonist antibody is designed to actively polarize TAMs to express NOS2, which mediate tumor clearance through an NOS2-dependent cytotoxicity. Moreover, OX40-antibody-mediated regulatory T cell (Treg) depletion potentiated NOS2+ macrophage induction. This multimodal strategy offers a promising solution to overcome the limitations of OX40 antibody monotherapy and enhance outcomes of the OX40-targeted immunotherapies.