Bapotulimab (BAY-1905254) is a mouse/human cross-reactive monoclonal antibody of the IgG2 isotype. It is classified as an immune checkpoint inhibitor being developed for cancer immunotherapy. Its mechanism of action involves blocking the Immunoglobulin-Like Domain Containing Receptor 2 (ILDR2). By binding to and inhibiting ILDR2, which normally exerts an immunosuppressive effect, Bapotulimab aims to lift the brake on T-cell activities. This leads to the induction of a cytotoxic T-lymphocyte (CTL) response against tumor cells, thereby restoring and enhancing the anti-tumor immune response. It has been investigated in Phase I clinical trials for advanced solid tumors, including in combination with PD-1 inhibitors like pembrolizumab.