A mouse/human cross-reactive immunoglobulin G2 (IgG2) monoclonal antibody against the immune checkpoint immunoglobulin-like domain containing receptor 2 (ILDR2; Chromosome 1 Open Reading Frame 32; C1orf32), with potential immune checkpoint inhibitory and antineoplastic activities. Upon administration, bapotulimab targets, binds to and inhibits ILDR2, thereby blocking the immunosuppressive activity of ILDR2. This prevents ILDR2-mediated inhibition of T-cell activities and induces a cytotoxic T-lymphocyte (CTL) response against tumor cells. ILDR2, a type I transmembrane protein belonging to the B7 family of immunomodulatory receptors, negatively regulates T-cell responses.