Suresh de Silva, George Fromm, Casey W Shuptrine, Kellsey Johannes, Arpita Patel, Kyung Jin Yoo, Kaiwen Huang and Taylor H Schreiber
Abstract for – CD40 Enhances Type I Interferon Responses Downstream of CD47 Blockade, Bridging Innate and Adaptive Immunity
Disrupting the binding of CD47 to SIRPα has emerged as a promising immunotherapeutic strategy for advanced cancers by potentiating antibody dependent cellular phagocytosis (ADCP) of targeted antibodies. Pre-clinically, CD47/SIRPα blockade induces antitumor activity by increasing the phagocytosis of tumor cells by macrophages and enhancing the cross-presentation of tumor antigens to CD8+ T cells by dendritic cells; both of these processes are potentiated by CD40 signaling. Here we generated a novel, two-sided fusion protein incorporating the extra cellular domains of SIRPα and CD40L, adjoined by a central Fc domain, termed SIRPα-Fc-CD40L. SIRPα-Fc-CD40L bound CD47 and CD40 with high affinity and activated CD40 signaling in the absence of Fc receptor cross-linking. No evidence of hemolysis, hemagglutination or thrombocytopenia was observed in vitro or in cynomolgus macaques. Murine SIRPα-Fc-CD40L outperformed CD47 blocking and CD40 agonist antibodies in murine CT26 tumor models and synergized with immune checkpoint blockade of PD1 and CTLA4. SIRPα-FcCD40L activated a type I interferon response in macrophages and potentiated the activity of ADCP-competent targeted antibodies both in vitro and in vivo. These data illustrated that whereas CD47/SIRPα inhibition could potentiate tumor cell phagocytosis, CD40-mediated activation of a type I interferon response provided a bridge between macrophage and T cell mediated immunity that significantly enhanced durable tumor control and rejection
