This is a humanized IgG4 antibody using the same sequences as the therapeutic antibody tislelizumab. It was designed to bind to PD1, a cell surface receptor that plays an important role in allowing tumor cells to evade the immune system. Tislelizumab can potentially restore the ability of CTLs to kill cancer cells by binding to PD1, without activating the receptor, thereby preventing PDL1 from engaging PD1. It is specifically designed to minimize binding to FcγR on macrophages. In pre-clinical studies, binding to FcγR on macrophages has been shown to compromise the anti-tumor activity of PD1 antibodies through activation of antibody-dependent macrophage-mediated killing of T effector cells. Tislelizumab is being developed as a monotherapy and in combination with other therapies for the treatment of a broad array of both solid tumor and hematologic cancers.