In the process of developing imaging probes and near-infrared (near-IR) fluorophores to aid in the identification of cancerous tumors, senior investigator in the Molecular Imaging Program at the National Cancer Institute/National Institutes of Health (NIH; Bethesda, MD) and leader of the Laboratory of Molecular Theranostics (LMT) Hisataka Kobayashi and LMT colleagues discovered a new dye (IRDye700DX) that is highly lethal to cancer cells when conjugated to an antibody.Unlike standard photodynamic therapy (PDT), the dye does not need to be internalized by the cell, but is applied to the cell membrane and activated with low-energy (150 mW/cm2) deep-red light (690 nm) from an LED or a laser system, effectively killing cancer cells through necrosis and stimulating the release of antigenic intracellular contents that initiate immunity against surviving cancer cells, even at some distance from the killed cells. Tumors in both mice and humans were seen to shrink beginning 24 hours after treatment.
This patented near-IR photoimmunotherapy (NIR-PIT) was licensed by the NIH to Rakuten Medical (San Mateo, CA), which raised $284 million in Series C financing in late 2018 and has since received Fast Track designation by the FDA for a Phase 3 trial to evaluate NIR-PIT therapy to treat recurrent head and neck squamous cell carcinomas. Reference: H. Kobayashi, Proc. SPIE, 10893, 1089302 (Mar. 4, 2019).