Photodynamic therapy using mono-L-aspartyl chlorin e6 for rabbit experimental hepatoma

Photodynamic therapy and photodynamic diagnosis using photosensitizers have yet to be clinically employed for hepatoma. Mono-L-aspartyl chlorin e6, a chlorin derivative with high tumor affinity developed as a second-generation photosensitizer, enables rapid tumor detection after administration, without light-shielding. This study examined the potential of photodynamic therapy, using this photosensitizer, for hepatoma in rabbits. VX2 tumor cells were transplanted into the liver of Japanese white rabbits, and the animals were administered 2.5 mg/kg of mono-L-aspartyl chlorin 36 1 week later. Accumulation of mono-L-aspartyl chlorin e6 in hepatoma was observed over time with an epifluorescence stereoscope, and the efficacy of continuous photodynamic therapy following photodynamic diagnosis was examined. A diode laser system was used for treatment, and efficacy was examined in a control group and four other groups that were irradiated at different times following administration. Efficacy in suppressing tumor growth, tumor necrosis rates, and efficacy in suppressing pulmonary metastasis were studied. For all these aspects, treatment was significantly more effective in the group irradiated 5 minutes after administration than in groups irradiated at later times. Liver function testing in all groups revealed no distinct disorders. Photodynamic therapy with mono-L-aspartyl chlorin e6 may be suitable for clinical use in therapy for hepatoma.