Abstract 1496: Novel hCD3e mouse models for preclinical pharmacology studies of therapeutic bi-specific antibodies

Abstract

Abstract Recently it has been demonstrated that T cell-mediated immunotherapy is an attractive treatment strategy for various diseases. For this therapeutic approach, the CD3 complex is one of the key targets to modulate T cell activation; however, in many instances we cannot directly evaluate antibody candidates in mice because the monoclonal antibodies specific to human CD3 cannot cross-react to mouse endogenous CD3. In order to overcome the current model limitation, we have generated CD3e-extracellular domain KI mice for anti-human CD3e bispecific antibody in vivo efficacy evaluation. In this model, the mouse CD3e extracellular domain was replaced by human CD3e. We used conventional mouse ES/HR technology to knock-in human CD3e genomic DNA from the 3’ end of exon 2 to the 5’ end of exon7 to replace murine exon 2-exon 6. CD3e is one of four subunits of the CD3 co-receptor, which plays an important role in the immune response, associating with the T cell receptor (TCR) to couple antigen recognition to intracellular signal transduction, leading to T cell activation. We have characterized our B-hCD3e mice with the following features: 1.Mouse CD3e+ cells were detected in the wildtype C57BL/6 mice, while human CD3e+ cells were only detected in the homozygous B-hCD3e mice. 2.T cell development was normal in B-hCD3e homozygous mice. 3.T cell subtypes in the spleen, thymus, lymph nodes, and PBMC in B-hCD3e mice were similar and comparable to that in wildtype C57BL/6 mice. 4.Normal in vitro T cell proliferation and cytokine production were found in anti-hCD3e antibody treated humanized B-hCD3e mice 5.Mouse anti-PD-1 antibody can significantly repress the growth of MC38 tumor cells engrafted on B-hCD3e mice, suggesting that T cells in B-hCD3e mice are functionally normal 6.Treatment of B-hCD3e mice with anti-human CD3e antibody OKT leads to T cell depletion, resulting in more aggressive tumor growth. Furthermore, efficacy and toxicity evaluation of CD3e based bispecific antibodies in B-hCD3e mice are ongoing. Based on our data from extensive phenotypical analyses of B-hCD3e mice, we believe this novel humanized CD3e mouse model will be very useful for in vivo efficacy studies of CD3- mediated therapy, especially anti-CD3e bi-specific antibodies. Citation Format: Jie Xiang, Yanan Li, Yuelei Shen, Yanan Guo. Novel hCD3e mouse models for preclinical pharmacology studies of therapeutic bi-specific antibodies [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 1496.