Extensive functional comparisons between chimeric antigen receptors and T cell receptors highlight fundamental similarities

CLDN18.2-targeting STAR-T cell therapy for pancreatic cancer: a strategy to minimize gastric off-tumor toxicity compared to CLDN18.2 CAR-T

Claudin18 isoform 2 (CLDN18.2), primarily expressed in gastric tissue and upregulated in pancreatic cancer (PC), is a key target for innovative treatments like chimeric antigen receptor T (CAR-T) cell therapy. However, CAR-T's effectiveness comes with a significant risk of on-target, off-tumor (OTOT) toxicity due to CLDN18.2's presence in normal gastric mucosa. To address this, we developed CLDN18.2-specific synthetic T cell receptor and antigen receptor T (STAR-T) cells. Our research shows that STAR-T and CAR-T cells have comparable in vitro cytotoxicity, but STAR-T cells cause less gastric damage in vivo despite having weaker antitumor effects than CAR-T cells. Clinical tests with gastroscopes confirmed the gastric safety of STAR-T cell therapy, which effectively controlled the disease. Additionally, incorporating the IL12β p40 subunit into STAR-T cells enhanced their function in both lab and animal studies. This evidence suggests that CLDN18.2 STAR-T cell could be a safer alternative to CAR-T cell therapy for PC, meriting further clinical trials.

De novo functional discovery of peptide-MHC restricted CARs from recombinase-constructed large-diversity monoclonal T cell libraries

Chimeric antigen receptors (CAR) that mimic T cell receptors (TCR) on eliciting peptide-major histocompatibility complex (pMHC) specific T cell responses hold great promise in the development of immunotherapies against solid tumors, infections, and autoimmune diseases. However, broad applications of TCR-mimic (TCRm) CARs are hindered to date largely due to lack of a facile approach for the effective isolation of TCRm CARs. Here, we establish a highly efficient process for de novo discovery of TCRm CARs from human naïve antibody repertories by combining recombinase-mediated large-diversity monoclonal library construction with T cell activation-based positive and negative screenings. Panels of highly functional TCRm CARs with peptide-specific recognition, minimal cross-reactivity, and low tonic signaling were rapidly identified towards MHC-restricted intracellular tumor-associated antigens MAGE-A3, NY-ESO-1, and MART-1. Transduced TCRm CAR-T cells exhibited pMHC-specific functional avidity, potent cytokine release, and efficacious and persistent cytotoxicity. The developed approach could be used to generate safe and potent immunotherapies targeting MHC-restricted antigens.

Further investigation of blockade effects and binding affinities of selected natural compounds to immune checkpoint PD-1/PD-L1

The breakthrough in the discovery of immune checkpoint PD-1/PD-L1 inhibitors, such as the series of Bristol Myers Squibb synthetic compounds, boosted the research of small molecules with blockade effects on the interaction of PD-1/PD-L1. However, the search for natural products derived PD-1/PD-L1 inhibitors can be impeded by the false positive and/or negative results from the screening assays. Herein, we combined a PD-1/PD-L1 blockade assay (pair ELISA) and a PD-L1/PD-L1 binding assay (surface plasmon resonance; SPR) to evaluate a panel of natural compounds previously reported to show anti-PD-1/PD-L1 activity. The test compounds included kaempferol, cosmosiin, tannic acid, pentagalloyl glucose, ellagic acid, resveratrol, urolithin A, and rifubutin. Based on the analyses of their responses to the combined screening assays, these compounds were categorized into four groups: I) PD-1/PD-L1 inhibitors that can bind to PD-1 and PD-L1; II) PD-1/PD-L1 inhibitors selectively bind to PD-L1 protein; III) PD-1/PD-L1 inhibitors without binding capacity, and IV) PD-1/PD-L1 binders without blockade effect. Discrimination of positive responders in the PD-1/PD-L1 blockade and binding assays can provide useful insights to avoid false outcomes. Examples demonstrated in this study suggest that it is crucial to adopt proper evaluation methods (including using multiple-facet functional assays and target binding techniques) for the search for natural products derived PD-1/PD-L1 inhibitors.