Photodynamic activity of lutetium-texaphyrin in a mouse tumor system

Background and Objective: New photosensitizers proposed for photodynamic therapy (PDT) treatment of tumors need to be evaluated in animal models to determine the parameters needed for treatment. They also need to be compared with existing photosensitizers for efficacy. We examined the PDT response to lutetium-texaphyrin (PCI-0123) in a mouse mammary adenocarcinoma model and compared it with the PDT response seen when using Photofrin®. Study Design/Materials and Methods: DBA/2 mice with SMT-F tumors were used to explore PCI-0123 toxicity, laser light dose, and drug dose effects on PDT response and to determine the most effective time for light application. The PDT response of PCI-0123-treated tumors was compared with that of Photofrin®-treated tumors. Results: Treatment of tumors with 150 J/cm² of 740 nm laser light 5-6 hr after PCI-0123 administration (40 mg/kg) resulted in a 100% response rate and a 55% cure rate. Tumors treated with 150 g/cm² of 630 nm laser light 24 hr after Photofrin® administration (10 mg/kg) resulted in a 67% response rate and a 16% cure rate. Conclusion: PCI-0123 was found to be a more effective photosensitizer than Photofrin®.