Humanization of a strategic CD3 epitope enables evaluation of clinical T-cell engagers in a fully immunocompetent in vivo model
Julie A. Zorn, Matthew L. Wheeler, Ralston M. Barnes, Jim Kaberna, Winse Morishige, Marek Harris, Richard Y.‐C. Huang, Jack Lohre, Yu Chang, Bryant Chau, Kathleen Powers, Ian Schindler, Naveen K. Neradugomma, Winston S. Thomas, Xiaoyun Liao, Yinhan Zhou, Sean M. West, Feng Wang, Srikanth Kotapati, Guodong Chen, Sayumi Yamazoe, Anastasia Kosenko, Gavin Dollinger, Tim W. Sproul, Arvind Rajpal, Pavel Strop
Abstract
T-cell engagers (TCEs) are a growing class of biotherapeutics being investigated in the clinic for treatment of a variety of hematological and solid tumor indications. However, preclinical evaluation of TCEs in vivo has been mostly limited to xenograft tumor models in human T-cell reconstituted immunodeficient mice, which have a number of limitations. To explore the efficacy of human TCEs in fully immunocompetent hosts, we developed a knock-in mouse model (hCD3E-epi) in which a 5-residue N-terminal fragment of murine CD3-epsilon was replaced with an 11-residue stretch from the human sequence that encodes for a common epitope recognized by anti-human CD3E antibodies in the clinic. T cells from hCD3E-epi mice underwent normal thymic development and could be efficiently activated upon crosslinking of the T-cell receptor with anti-human CD3E antibodies in vitro. Furthermore, a TCE targeting human CD3E and murine CD20 induced robust T-cell redirected killing of murine CD20-positive B cells in ex vivo hCD3E-epi splenocyte cultures, and also depleted nearly 100% of peripheral B cells for up to 7 days following in vivo administration. These results highlight the utility of this novel mouse model for exploring the efficacy of human TCEs in vivo, and suggest a useful tool for evaluating TCEs in combination with immuno-oncology/non-immuno-oncology agents against heme and solid tumor targets in hosts with a fully intact immune system.