Study of the in vivo and in vitro photosensitizing capabilities of uroporphyrin I compared to photofrin II.

The in vivo biological activity of uroporphyrin I has been studied by determining the amount of necrosis produced in murine tumors exposed to various total doses of light at 615 nm. Similarly, the in vitro photosensitizing activity of uroporphyrin I was examined by measuring the percentage of cells killed in a cell culture system. Light doses used were 25-400 J/cm2. Mice that received uroporphyrin I at 40 mg/kg had only minimal superficial necrosis upon histological examination at doses of 400 J/cm2 (615 nm). Those tumors that received 300 J/cm2 or less showed no histological evidence of necrosis. Mice that received hematoporphyrin derivative (Photofrin II) at 10 mg/kg were completely necrotic at total doses of 100 J/cm2 (630 nm). PTK2 epithelial cells incubated with uroporphyrin I at either 40 micrograms/ml or 80 mu/ml and 10 J/cm2 (615 nm) showed no apparent damage and had 100% cell survival. By contrast, those cells treated with hematoporphyrin derivative (Photofrin II) at 25 micrograms/ml and 10 J/cm2 (630 nm) exhibited 100% cell kill. It is concluded that uroporphyrin I is a poor photosensitizer in both in vivo and in vitro systems compared to hematoporphyrin derivative (Photofrin II).