Photodynamic therapy (PDT), which is also called as photochemotherapy, is a technique for treating incurable disease such as cancer without operation or treating skin disease such as acne by the use of a photosensitizer. There has been active study about PDT since the early twentieth century. Currently, PDT is used to increase immunocompetence in diagnosis and treatment of cancer, autologous bone marrow transplantation, antibiotics, AIDS treatment, skin graft or treatment of arthritis and the like, and so its applications have been gradually expanded. Specifically, PDT used in the treatment of cancer is a therapeutic method utilizing a principle in which a photosensitizer—which is a chemical compound showing sensitivity to light—is administered to the body; when it is exposed to external light, singlet oxygen or free radicals are generated via the chemical reaction by rich oxygen in the body and external light; and then such singlet oxygen or free radicals destroy various lesion sites or cancer cells by inducing cell death.
As photosensitizers used in PDT, porphyrin derivatives, chlorin, bacteriochlorin, phthalocyanine, 5-aminolevulinic acid derivatives and the like are known. Cyclic tetrapyrrole derivatives as photosensitizers also have properties for being utilized as agents for early diagnosis of tumor since they show fluorescence and phosphorescence according to their chemical properties as well as being selectively accumulated to cancer cells. In addition, metalloporphyrin, in which metal is bound to the interior of cyclic tetrapyrrole, shows various properties according to the kind of bound metal, thereby being applied to early diagnosis of tumor cells such as cancer cells by use of a diagnostic technique wherein metalloporphyrin is used as an MRI (magnetic resonance imaging) contrasting agent. 5-Aminolevulinic acid derivatives, which are the most widely known photosensitizers, have advantages wherein the method of use is simple, they can relatively easily penetrate into the skin due to small molecular weight, and they are safe with few side effects. Furthermore, one of the photosensitizers receiving attention is a chlorin-type photosensitizer, chlorin e6. As an example of the composition using chlorin e6, Korean Patent Application No. 10-2006-0136610 discloses antitumoric compositions for oral administration comprising chlorin e6 or a pharmaceutically acceptable salt thereof as an active ingredient.
As explained above, usage in the treatment of skin diseases such as acne was suggested as one of the applications of PDT, but no report has been made about its successful application.