(D)-PPA 1 TFA

(D)-PPA 1 TFA is a hydrolysisresistant d-peptide antagonist. (D)-PPA 1 TFA serves as a potent PD-1/PD-L1 inhibitor. (D)-PPA 1 TFA binds to PD-1 with the affinity 0f 0.51 μM with in vitro and in vivo efficacy.