Development of a Peptide-Based Photoimmunotherapy Drug Targeting PD-L1

Near-infrared photoimmunotherapy (NIR-PIT) has recently attracted attention as a highly selective cancer treatment, with good treatment outcomes observed from the only antibody-based drug currently available for clinical use. However, since only a single agent is currently used clinically and the development of new antibodies is costly, exploring other therapeutic modalities is important. In this study, we investigated a novel peptide-based PIT drug targeting programmed death ligand 1 (PD-L1), which is overexpressed in many types of cancer. The WL12 peptide, which is known to bind to PD-L1, was conjugated with the photoabsorber IRDye700DX (IR700), and its usefulness was evaluated in vitro and in vivo. In therapeutic experiments on PD-L1-positive cells, NIR-PIT with WL12-IR700 induced PIT-like morphological changes in cells and reduced cancer cell viability in an NIR light dose- and drug concentration-dependent manner. In vivo experiments showed significant suppression of tumor growth and an extended overall survival rate. These results indicate that the developed peptide-based drug can be used for PD-L1-targeted NIR-PIT.