The IgG4 anti‐PD‐1 antibody tislelizumab has had its FcγR contact residues in the lower hinge E233, F234, L235 substituted with the equivalent residues of IgG2 P, V, A (E233P, F234V, L235A) as well as the additional D265A mutation which disrupts a major FcγR contact in CH2.