Recent success of immune checkpoint inhibitors (CPIs) in the clinic underscores the role of cancer immune surveillance and the therapeutic potential of targeting immune receptors. Unlike CPIs, many members of the TNF receptor superfamily (TNFRSF), e.g., CD40, 4-1BB, OX-40, and GITR deliver agonistic signals to immune cells that may directly activate antitumor immune responses and, in combination with CPIs, may improve outcomes of active immunotherapy. Sugar-Engineered Antibody (SEA)-CD40 is a non-fucosylated, humanized IgG1 anti-human CD40 monoclonal antibody currently being evaluated in a phase 1 clinical trial in solid tumors and lymphoma. It binds FcγR3A with higher affinity and demonstrates enhanced immune stimulatory activity compared to its parent dacetuzumab. An SEA version of an anti-mouse CD40 antibody (mouse IgG2a), SEA-1C10, has been generated. As expected, SEA-1C10 bound to mouse FcγRIV, the functional homolog of human FcγR3A in mice, at a higher affinity than parent 1C10. Enhanced FcγRIV engagement by SEA-1C10 translated into stronger antitumor activity in the CD40 (-) B16F10 melanoma and CD40 (+) A20 lymphoma models. In the A20 model, tumor free mice that survived the initial A20 tumor implantation and SEA-1C10 treatment were re-challenged with live A20 cells. Twenty nine out of thirty one such tumor free mice rejected A20 tumor re-engraftment, suggesting that a strong memory immune response was elicited by SEA-1C10 treatment. The SEA-1C10/anti PD-1 combination also showed greater antitumor activity compared to SEA-1C10 or anti-PD-1 alone, supporting the hypothesis that stimulation of antigen-presenting cells by agonistic CD40 signaling can complement immune checkpoint inhibition. In addition, a transgenic (TG) mouse strain has been generated in which the endogenous Cd40 locus is inactivated by the targeted insertion of a human-mouse chimeric CD40 gene. This allows for incorporation of the extracellular domain of human CD40 while keeping the transmembrane and cytoplasmic domains of mouse CD40. Lineage-restricted expression of the CD40 TG on B cells and monocytes was confirmed. CD40 TG cells responded to SEACD40-mediated agonistic signaling in vitro by secreting CD40 signature cytokines and up-regulating the costimulatory molecules CD86 and MHC class II. Treatment of CD40 TG animals with SEA-CD40 resulted in cytokine induction and B-cell depletion. Similar to studies in human PBMCs and non-human primates, SEA-CD40 induced more robust cytokine production and immune cell activation than its fucosylated parent dacetuzumab. These experimental systems will be further applied to address clinically important questions including mechanism(s) of anti-tumor effects, biomarkers indicating immune activation, dosing strategies, and timing of combinatorial regimens with CPIs.

Citation Format: Shyra J. Gardai, Weiping Zeng, Che-Leung Law. Therapeutic activity of effector function-enhanced, non-fucosylated anti-CD40 antibodies in preclinical immune-competent rodent tumor models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3647. doi:10.1158/1538-7445.AM2017-3647