Pharmacokinetic Study of a Gallium‐porphyrin Photo‐ and Sono‐sensitizer, ATX‐70, in Tumor‐bearing Mice

The tissue distribution of a gallium‐porphyrin photo‐ and sono‐sensitizer, 7,12‐bis(l‐decyloxy‐ethyl)‐Ga(III)‐3,8,13,17‐tetramethylporphyrin‐2,18‐dipropionyldiaspartic acid, ATX‐70, was phar‐niacokinetically examined in tumor‐bearing mice. The drug was administered intravenously to CDF1mice implanted with Colon 26 carcinoma. Blood and tissue samples were collected for up to 72 h after administration. The drug concentration was determined by high‐performance liquid chromatography (HPLC) with fluorescence detection. ATX‐70 was found to accumulate in tumors at a relatively high concentration that peaked between 2 h and 6 h after administration. However, modest concentrations of ATX‐70 also remained in healthy tissues for up to 6 h. We examined the distribution of ATX‐70 in the tumor in comparison with other tissues from the viewpoint of minimizing possible side effects of laser or ultrasound exposure while maintaining the treatment effect. About 24 h after administration, the tumor/plasma concentration ratio peaked, and relatively high tumor/skin and tumor/muscle concentration ratios were seen.