Photodynamic therapy using a novel photosensitizer, TONS501, is similarly effective to ALA and EC036 photodynamic therapy on DMBA-and TPA-induced mouse skin papilloma

Abstract Background Although topical photodynamic therapy (PDT) using 5-aminolevulinic acid (ALA) is applied for skin tumors including actinic keratosis, Bowen disease, and squamous cell carcinoma, there are no approved photosensitizers in dermatological field in Japan. TONS501 and TONS504 are novel hydrophobic photosensitizers with anionic and cationic chemical characteristics, respectively. Objective Using 7, 12-dimethylbenz[a]anthracene (DMBA) and 12- ο -tetradecanoylphorbol-13-acetate (TPA)-induced mouse skin papilloma model, we compared the efficacy of ALA-, TONS501-, and TONS504-PDT on the skin tumor regression. Methods Following application of ALA, TONS501, TONS504 ointment or TONS501 lotion on DMBA- and TPA-induced mouse papillomas, 670 nm laser irradiation by LD670-05 diode laser was performed. Then tumor regression rate was calculated at the indicated time. Results The anti-tumor effect of ALA, TONS501, and TONS504 ointment was detected at 24 h and the maximal response was observed at 3 day following the PDT treatment. The maximal response was observed at 150 J/cm 2 irradiation in all 3 photosensitizers. Although both ALA, TONS501 (ointment)-PDT showed more potent anti-tumor effect compared with that of TONS504 ointment or TONS501 lotion, no significant difference was detected between ALA ointment and TONS501 ointment. Conclusion A novel TONS501ointment-PDT shows potent anti-tumor effect on DMBA- and TPA-induced mouse skin papilloma and might be more useful for the clinical applications.