Tislelizumab (BGB-A317) is a humanized IgG4 monoclonal antibody targeting the PD-1 immune checkpoint [5
]. It contains an alternative hinge region compared to other IgG4 anti-PD-1 antibodies, and subsequently does not induce the crosslinking between PD-1 and FcγRI that is observed for existing agents and which is believed to negatively impact on anti-PD-1 antibody-mediated anti-cancer activity. This modified profile is predicted to enhance tislelizumab's clinical efficacy [5
]. Like other anti-PD-1 antibodies tislelizumab acts to prevent the binding of the ligands PD-L1 and PD-L2 to PD-1. Tislelizumab is an immuno-oncology drug candidate that was originally developed by Beigene (see their patent US8735553B1 [4
]), and Novartis announced that they had acquired the rights to tislelizumab in major markets outside China in January 2021.