Selective in vivo tumor localization of heptacarboxylic porphyrin isomer I in a bladder tumor model: a novel technique to modulate porphyrin localization.

We were the first to report that uroporphyrin isomer I is a superior tumor localizer when compared with hematoporphyrin derivative. In the present study, we have examined the tumor localization of heptacarboxylic porphyrin isomer I (hepta-P) using a bladder tumor model. We have also compared it to that found with uroporphyrin isomer I (Uro-P). We now show, for the first time, that (hepta-P) isomer I can be selectively retained in bladder malignant cells, a novel observation which has not yet been described by other investigators. Furthermore, we have provided a novel technique to modulate and manipulate blood protein binding to porphyrin in a controlled manner, such that the tumor localization properties can be effectively utilized without prolonged retention in the skin and to produce high uptake in the tumor, i.e., a higher therapeutic ratio. The biodistribution of hepta-P in different organs is presented.