Fcgamma-receptor-independent controlled activation of CD40 canonical signaling by novel therpeutic antibodies for cancer therapy

Activation of CD40-mediated signaling in antigen-presenting cells is a promising therapeutic strategy to promote immune responses against tumors. Agonistic anti-CD40 antibodies currently in development require Fc{gamma}-receptor-mediated crosslinking of CD40 molecules for meaningful activation of CD40 signaling but have limitations due to dose-limiting toxicities. Here we describe the identification of CD40 antibodies which strongly stimulate antigen-presenting cells in an entirely Fc-independent manner. These novel Fc-silenced anti-CD40 antibodies induce upregulation of costimulatory receptors CD80 and CD86 and cytokine release by dendritic cells with an efficacy exceeding that of existing antibodies. Binding to the CD40L interaction region on CD40 appears to be a prerequisite to achieving such strong activities. Finally, the most active identified anti-CD40 antibody shows evidence of activity in terms of the expected markers of canonical CD40 signaling when injected in humanized mice. There are no signs of obvious toxicities whereas the clinical-stage anti-CD40 antibody CP-870,893 induced severe signs of toxicity in these animals despite a lower dose compared with the novel Fc-silenced canonical agonist. These studies thus demonstrate potent activation of antigen-presenting cells with anti-CD40 antibodies lacking Fc{gamma}-receptor-binding activity and open the possibility of an efficacious and safe combination therapy for cancer patients. One Sentence SummaryTreatment of antigen-presenting cells and humanized mice with novel Fc-silenced CD40 antibodies demonstrates an Fc{gamma}-receptor-independent canonical agonistic mode of action for therapeutic use.