Used in cancer immunotherapy research, particularly for hepatocellular carcinoma (HCC) and other GPC3-expressing tumors. Due to its modified form with serine-to-alanine mutations and Fc tag, it serves as a critical reagent in binding assays, antibody screening, and immunoassay development. It helps evaluate the affinity and specificity of anti-GPC3 antibodies or chimeric antigen receptors (CARs) used in CAR-T cell therapies. Also employed as a detection standard in ELISA, flow cytometry, and surface plasmon resonance (SPR) to support diagnostic and therapeutic development. Its Fc tag enables easy detection and purification using anti-Fc secondary reagents and protein A/G systems.