Abstract: Objective The blood group-related antigen Lewis y is highly expressed in various tumors, and its humanized monoclonal antibody Hu3S193 has been applied in clinical trials as an anti-tumor drug. Previous studies have confirmed the presence of Lewis y antigen on the surface of human platelets, yet the effect of Hu3S193 on platelet function remains unclear. This study aimed to explore the regulatory effect of Hu3S193 on the in vitro functions of human platelets, providing experimental evidence for the safety and mechanism of its clinical anti-tumor application. Methods Flow cytometry was used to verify the in vitro binding ability of Hu3S193 to human platelets. The release of platelet α-granules was evaluated by detecting P-selectin expression, and the intracellular calcium concentration ([Ca²⁺]i) of platelets was measured using Fluo-3 fluorescent probe to analyze the effect of Hu3S193 on platelet activation with or without thrombin stimulation. Thromboelastography (TEG) was performed to detect platelet coagulation function, and flow adhesion assay was used to assess the adhesion ability of platelets to type Ⅰ collagen. Results In vitro experiments confirmed that Hu3S193 could specifically bind to human platelets in a concentration-dependent manner. Hu3S193 at clinical dose (5 μg/mL) and higher concentrations (10, 20 μg/mL) had no significant effect on platelet α-granule release and did not induce abnormal platelet activation. TEG detection showed that 5 μg/mL Hu3S193 had no obvious change on maximum amplitude (MA), the core index of platelet coagulation function. In the absence of thrombin stimulation, clinical-dose Hu3S193 significantly increased platelet intracellular calcium concentration and inhibited thrombin-induced calcium influx activation. Flow adhesion experiments verified that Hu3S193 inhibited the flow adhesion ability of platelets to type Ⅰ collagen in a dose-dependent manner. Conclusion Hu3S193 does not affect the basal activation and coagulation function of human platelets. but can regulate platelet intracellular calcium level and significantly inhibit platelet flow adhesion. This finding supplements a new theoretical basis for its anti-tumor mechanism and provides a reference for its clinical safe medication.

Key words: Lewis y antigen, Hu3S193 monoclonal antibody, Platelet, Cell adhesion, Coagulation function