PD-L1Pep-2 was identified from a phage-displayed library for peptides that selectively bind to PD-L1-overexpressing cells. PD-L1Pep-2 has a binding affinity of 281 nM, and preferentially binds to high PD-L1-expressing cells over low PD-L1-expressing cells, binding further enhanced by interferon-i, an inducer of PD-L1 expression. In animal models, intravenously injected PD-L1Pep-2 efficiently targets tumour tissues, inhibits tumour growth, and increases the CD8+/FoxP3+ ratio in mice. PD-L1Pep-2 in combination with doxorubicin inhibits tumour growth more efficiently than doxorubicin alone. PD-L1Pep-2 blockade of PD-L1 reinvigorates T-cell activity and inhibits tumour growth by enhancing anti-tumour immunity.
