Cancer Cell-Selective In Vivo Near Infrared Photoimmunotherapy Targeting Specific Membrane Molecules

Three major modes of cancer therapies, surgery, radiation and chemotherapy, have been the mainstay of modern oncologic therapy. To minimize side effects, molecular targeted cancer therapies including armed antibody therapy have been developed with limited success. In this study, we developed a new type of molecular targeted cancer therapy, photoimmunotherapy (PIT), employing a target-specific photosensitizer based on a near infrared (NIR) phthalocyanine dye, IR700, conjugated to monoclonal antibodies (MAb) targeting epidermal growth factor receptors (EGFR). Cell death was induced immediately only upon irradiating, MAb-IR700 bound, target cells with NIR light. In vivo tumor shrinkage after irradiation with NIR light was observed only in target EGFR-expressing cells. The MAb-IR700 conjugates were most effective when bound to the cell membrane, producing no phototoxicity when not bound, suggesting a different mechanism for PIT compared with conventional photodynamic therapies. Target selective PIT enables treatment of cancer based on MAb binding on the cell membrane.