PD-1/PD-L1 Inhibitor is a macrocyclic inhibitor of PD-1/PD-L1 interaction with an IC50 of 5.6 nM. In vitro ab231310 is capable of inhibiting the interaction of PD-L1 with PD-1 and with CD80. It has highly efficacious binding to PD-L1 and promotes enhanced T cell functional activity.