CLDN18.2-positive Advanced Solid Tumor

This study consists of two research phases: Phase Ib (includes dose escalation stage and efficacy expansion stage): To explore the safety, tolerability and initial efficacy of SHR-A1904 in the treatment of CLDN18.2-positive advanced solid tumors, and to determine the recommended dose and recommended population for the Phase III combination study. Phase III: A randomized, Open-Label, multicenter clinical study of SHR-A1904 combined with chemotherapy and immunotherapy Versus chemotherapy combined with immunotherapy for CLDN18.2-positive advanced solid tumors.