Background We have developed a proprietary T cell-based anti-CD3 T cell engager delivery platform (named CAB-T), which includes two elements: a chimeric CD3e/signaling component and a CD3-based bispecific T cell engager (TCE). We have previously shown the efficacy vs. safety advantages of the CAB-T system over a traditional second-generation CAR-T format by targeting claudin18.2 (CLDN18.2) (poster no. 206, SITC2021). However, a comprehensive comparison between CAB-T vs. CAR-T had not been investigated. Here, in multiple independent in vivo tumor mouse models, we aimed to assess the safety and efficacy of our CAB-T platform using CLDN18.2-CAB-T cells.
Methods A sequence encoding for an anti-human CLDN18.2 scFv was engineered into CAB-T (CLDN18.2-CAB-T) and CAR-T (CLDN18.2-CAR-T) expression systems and generated via lentiviral transduction of T cells followed by cell expansion. Cytokine release and TCE levels were determined by ELISA and a cytometric bead array, while T cell killing was tested by the detection of LDH release. In vivo studies using CLDN18.2+ tumor cells were tested in humanized mouse models (NCG or NOG mice). T cell infiltration into tumors or normal gastric tissue were detected by immunohistochemistry with an anti-FLAG antibody.
Results Both CLDN18.2-targeting CAB-T and CAR-T cells displayed excellent dose-dependent in vivo anti-tumor efficacy towards CLDN18.2-positive tumor cells. However, CLDN18.2-CAB-T cells had a superior safety profile over its CAR-T equivalent. More specifically, mid (1 x 106 cells) to high (5 x 106 cells) single doses of CLDN18.2-CAR-T cells were lethal to mice, whereas all the dose levels of CAB-T cells were safe. CLDN18.2-CAB-T cells released less inflammatory cytokines than CLDN18.2-CAR-T, including IL-6, TNFα and IL-2, in in vitro co-culture assays with NUGC4 tumor cell targets. Mice treated with CLDN18.2-CAB-T also showed higher levels of serum GM-CSF and IFNγ compared to those treated with CLDN18.2-CAR-T. Meanwhile, CLDN18.2-CAR-T induced severe immune cell infiltration in normal gastric tissue, whereas CLDN18.2-CAB-T did not. This suggests that CAB-T may provide a wider therapeutic dosing window than traditional CAR-T platforms.
Conclusions We show that CLDN18.2-CAB-T has superior safety traits over CLDN18.2-CAR-T while maintaining high levels of in vivo anti-tumor efficacy, suggesting that CAB-T cells may offer better safety for patients in the clinic. CLDN18.2-CAB-T is currently undergoing an investigator-initiated trial to test its safety and efficacy for subjects with CLDN18.2+ solid tumors.
Ethics Approval All mice were maintained under specified pathogen-free conditions, and all studies were approved by the Animal Care and Use Committee of HUST-Suzhou Institute for Brainsmatics.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.