GZMB and neoplasm: Bi-specific antibodies (BsAbs) concomitantly bind to two different antigens; one side binds to CD3 on T cells or CD16 on NK cells, and the other side binds to a tumor-specific antigen on tumor cells, which redirects the host immune system for cytotoxic T cell activation to secrete cytotoxic granules such as granzyme B, perforin and interferon, leading to exhibit effector cell-mediated cytotoxicity against tumor cells [45,46,47].