Translocator protein (TSPO)-Targeted agents for photodynamic therapy of cancer

Photodynamic therapy (PDT) is a clinically approved therapeutic strategy that combines a specific wavelength of light and light-activated photosensitizers (PSs). The usage of PDT for cancer treatment is often hampered by the lack of tumor selectivity of PSs, which may cause photodamage to surrounding normal tissues. Recently, translocator protein (TSPO) has attracted great interest as a tumor biomarker, whose expression correlates with tumor aggressiveness. In this study, we report the development of a series of novel TSPO-PSs based on quinazoline, pyrazolopyrimidine, and tetrahydrocarbazole structures. These TSPO-PSs bind to TSPO with nanomolar affinities and demonstrated efficient and target-specific PDT effect upon light irradiation. Therefore, they may have great potential in the treatment of tumors associated with high-TSPO expression.