Photodynamic Therapy Using IR-783 Liposomes for Advanced Tongue and Breast Cancers in Humans

Photodynamic therapy (PDT) is a minimally invasive treatment that elicits tumor apoptosis using laser light exclusively applied to the tumor site. IR-783, an HMC dye, impedes the proliferation of breast cancer cells, even without light. However, the mechanism by which IR-783 exerts its antiproliferative effects remains unclear. We aimed to determine the efficacy of PDT using IR-783 liposomes. A heptamethine cyanine (HMC) dye excited by long-wavelength infrared light and with high tissue permeability was used for PDT after liposomization to enhance tumor tissue accumulation. PDT was performed using IR-783 in two patients with tongue and breast cancers. IR-783 liposomes similarly inhibited cell proliferation in lung cancer cells even when not excited by light. Tumor size was markedly reduced in both cases, with no significant adverse events. Furthermore, the patient with tongue cancer exhibited improved respiratory, swallowing, and speech functions, which were attributed not only to the shrinkage of the tumor, but also to the improvement of airway narrowing. In conclusion, PDT using IR-783 liposomes effectively reduces tumor size in tongue and breast cancers.