Extracellular vesicle proteins monitor and interfere with CLDN18.2-targeted CAR-T cell and antibody therapies against gastrointestinal cancers.

Claudin 18.2 (CLDN18.2)-targeted CAR-T cell and antibody therapies show promise against gastrointestinal cancers, but biomarkers predictive of long-term benefit and therapeutic sensitization strategies are needed. Here we show that proteins carried by circulating extracellular vesicles (EVs) can reflect and influence the efficacy of CLDN18.2-targeted therapies. By profiling serial plasma samples of patients from the CT041-CG4006 trial (CLDN18.2- CAR-T-therapy) or the GLOW trial (Zolbetuximab), we identified EV-associated CLDN18.2, PD1 and PD-L2 as therapeutic markers and integrated them into a signature (CPP-score) for better predictive robustness. Mechanistically, specific EV-proteins exhaust CAR-T cells, neutralize CLDN18.2-targeted-antibodies, activate immunosuppressive IL-6-expressing cancer-associated fibroblasts, and alter the TH1/TH2 balance, thereby reshaping the tumor microenvironment and interfere with CLDN18.2-targeted therapies. Strategies including combining anti-PD1 antibody or CAF inhibitor, CLDN18.2-CAR-T plus CLDN18.2-antibody, and depleting plasma EVs, can sensitize CLDN18.2-CAR-T/antibody by countermeasuring EV-proteins' therapeutic interferences. Collectively, our work provides potential options to monitor and improve CLDN18.2-targeted therapies in clinical practice.