Blocking of the PD-1/PD-L1 Interaction by a D-Peptide Antagonist for Cancer Immunotherapy.

Blockade of the protein-protein interaction between the transmembrane protein programmed cell death protein 1 (PD-1) and its ligand PD-L1 has emerged as a promising immunotherapy for treating cancers. Using the technology of mirror-image phage display, we developed the first hydrolysis-resistant D-peptide antagonists to target the PD-1/PD-L1 pathway. The optimized compound DPPA-1 could bind PD-L1 at an affinity of 0.51 μ M in vitro. A blockade assay at the cellular level and tumor-bearing mice experiments indicated that DPPA-1 could also effectively disrupt the PD-1/PD-L1 interaction in vivo. Thus D-peptide antagonists may provide novel low-molecular-weight drug candidates for cancer immunotherapy. [ABSTRACT FROM AUTHOR]