132-hydroxy-bacteriopheophorbidea-methylester pharmacokinetics in mice bearing Lewis lung carcinoma

Abstract

The photosensitiser 13²-hydroxy bacteriopheophorbide a-methylester (13²-OH-BPME) is characterised by a high absorption coefficient at the far red wavelength 750 nm and a good singlet oxygen quantum yield. The pharmacokinetics of 13²-OH-BPME was studied on the Lewis lung carcinoma in mice after i.v. administration of 5 mg/kg body weight at different incubation intervals. The accumulation dye was chemically extracted from selected tissues and the concentrations were measured by absorption spectroscopy. The parenchymatous organs, liver, spleen and kidney, showed maximum 13²-OH-BPME concentrations after 2 h incubation (liver, spleen) and 4 h postinjection (kidney). A high uptake was detected in the lung with the maximum concentration at 2 h. The malignant tissue accumulated high 13²-OH-BPME concentrations at 2–12 h postinjection with peaking at 8 h. The 13²-OH-BPME concentrations in muscle tissue, representing the normal tumour surroundings, and in the skin were very low. The results of our study suggest that photodynamic therapy (PDT) using 13²-OH-BPME could be effective at an incubation time of about 8 h postsensitiser injection, when the tumour 13²-OH-BPME concentration has reached its maximum and the muscle and skin concentrations are at a minimum.