CD40 receptor is a member of TNF-receptor superfamily, broadly expressed on the surface of antigen-presenting cells (APC) including B cells, dendritic cells (DC), macrophages, monocytes, and non-APC like platelets, endothelial cells and even some tumor cells. CD40 is essential for APC activation and signalling via ligation of CD40 ligand located on helper T cells and CD40 on APC to mediate licensing (activating) of APC. Ligation of CD40 on DCs, for example, can induce increased surface expression of costimulatory and MHC molecules, production of pro-inflammatory cytokines, and enhanced T cell activation. CD40 ligation on resting B cells can increase its antigen-presenting function and proliferation. In contrast to its critical role in the induction of effective innate and adaptive immune responses, CD40 signalling on certain malignant cells, particularly B cell lymphomas, triggers tumor apoptosis. The dual function of CD40 signalling provide unique opportunities for the use of agonistic CD40 antibodies in cancer immunotherapy. Indeed, several CD40 monoclonal antibodies are now in different stages of clinical development, some shown promising preliminary results in combination with other cancer immunotherapies. However, we are lacking preclinical models to evaluate efficacy of therapeutic CD40 agonistic antibodies, which usually don’t cross-bind to mouse targets. To fill this gap, we developed a human CD40 knock-in model (CD40 HuGEMM), of which mouse exon 2-5 are replaced by human counterparts. These KI mice express a chimeric CD40 with human extracellular domain & mouse trans-membrane and intracellular sequences. We have characterized the human CD40 expression of CD40 HuGEMM on a broad spectrum of mouse cells, such as lymphocytes, macrophages, DCs, and endothelial cells. In addition, we confirmed that human CD40 antibodies bind to the chimeric m/hCD40 recombinant protein, and lead to increased expression of MHCII on the B cells. Finally, the in vivo efficacy study indicates that human CD40 antibody treatment lead to robust anti-tumor response and contribute to better survival of the mice. Taken together, our CD40 HuGEMM provides a powerful preclinical model to assess the efficacy of the human-specific CD40 agonistic antibodies. It may also serve as a model for proof of concept studies of CD40 agonistic antibodies with other therapies.

Citation Format: Daniel Xianfei He, Lei Zheng, Ruilin Sun, Annie Xiaoyu An, Jian Fei, Henry Qixiang Li, Davy Xuesong Ouyang. Ex vivo functional characterization and in vivo efficacy validation of human CD40 agonistic antibodies in the human CD40 knock-in model (CD40 HuGEMM) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4976.