Recent advances in near-infrared dye conjugates for near-infrared photoimmunotherapy (NIR-PIT): enhancing therapeutic efficacy and immune mechanisms.

Near-infrared photoimmunotherapy (NIR-PIT) is an innovative cancer treatment modality that was approved in Japan in 2020 for the treatment of unresectable locally advanced or locally recurrent head and neck cancer. This therapy uses an antibody-dye conjugate (Ab-IR700), which consists of a monoclonal antibody targeting a specific cell-surface antigen and a phthalocyanine-based near-infrared dye, IR700, that functions as a photosensitizer. After selective accumulation in tumor tissue, Ab-IR700 is irradiated with 690 nm NIR light, which initiates a photochemical reaction that selectively damages the cell membrane of target cells, thereby inducing immunogenic cell death. Its high tumor selectivity and therapeutic efficacy establish NIR-PIT as a promising next-generation cancer therapy. However, its further application to deep-seated solid tumors remains challenging, and will require IR700 analogs and novel dye scaffolds that can be activated by longer-wavelength light to achieve greater tissue penetration and that offer greater photochemical activation efficiency. This review covers the activation mechanism of IR700, the mechanisms of cytotoxicity of NIR-PIT, emerging applications of NIR-PIT in oncology and infectious diseases, the range of dye delivery vehicles, and the development of new dyes for NIR-PIT.