sintilimab + paclitaxel + S-1

This is a combination regimen consisting of three drugs: - **Sintilimab** is a fully human IgG4 monoclonal antibody targeting programmed cell death protein 1 (PD-1), functioning as an immune checkpoint inhibitor to enhance anti-tumor immune responses. - **Paclitaxel** (including its nanoparticle albumin-bound formulation, nab-paclitaxel) is a microtubule-stabilizing chemotherapeutic agent that inhibits cell division by promoting tubulin polymerization and preventing microtubule disassembly. - **S-1** is an oral fluoropyrimidine derivative combining tegafur (a prodrug of 5-fluorouracil), gimeracil, and oteracil potassium, designed to enhance the efficacy and reduce the gastrointestinal toxicity of 5-FU. The combination has been investigated primarily as adjuvant or second-line therapy for advanced or metastatic gastric cancer, especially in patients with peritoneal metastasis. The rationale for this triplet regimen is to combine immunotherapy with cytotoxic chemotherapy to achieve synergistic anti-tumor effects—chemotherapy can increase tumor antigen release and modulate the tumor microenvironment ("turning cold tumors hot"), thereby enhancing the efficacy of PD-1 blockade[1][9]. Clinical trials have demonstrated promising antitumor activity and manageable safety profiles for this combination in gastric cancer[1][9].