To overcome the limitation of conventional cancer treatments, photodynamic therapy (PDT) has been introduced as another treatment option. PDT provides a non-invasive, non-surgical way with reduced toxicity. To improve the antitumor efficacy of PDT, we synthesized a novel photosensitizer, a 3-substituted methyl pyropheophorbide-a derivative (Photomed). The purpose of the study was to evaluate the antitumor effect of PDT with Photomed comparing with the clinically approved photosensitizers Photofrin and Radachlorin. The cytotoxicity assay against SCC VII cells (murine squamous cell carcinoma) was performed to determine whether Photomed is safe without PDT and whether Photomed is effective against cancer cells with PDT. An in vivo anticancer efficacy study was also performed using SCC VII tumor-bearing mice. The mice were divided into small-tumor and large-tumor groups to identify whether Photomed-induced PDT is effective for not only small tumors but also large tumors. From in vitro and in vivo studies, Photomed was confirmed to be (1) a safe photosensitizer without laser irradiation, (2) the most effective photosensitizer with PDT against cancers compared to Photofrin and Radachlorin and (3) effective with PDT in treating not only small tumors but also large tumors. In conclusion, Photomed may contribute as a novel, potential photosensitizer for use in PDT cancer treatment.
Keywords: cancer treatment; chlorin derivative; novel photosensitizer; photodynamic therapy; pyrazole.