EU-103 is a humanized monoclonal antibody that targets V-Set And Immunoglobulin Domain Containing 4 (VSIG4), with a KD value range between 10^-7 and 10^-9. It disrupts the interaction between VSIG4 and CD8+ T cells, facilitating the transformation of M2 macrophages to M1 macrophages, inducing proliferation of CD8+ T cells, and promoting the secretion of pro-inflammatory cytokines, thereby inhibiting tumor growth. EU-103 shows potential for research in cancer treatment, including bladder cancer, breast cancer, and colon cancer.