PHOTOSENSITIZATION AND TISSUE DISTRIBUTION STUDIES OF THE PICKET FENCE PORPHYRIN, 3,1-TPRO, A CANDIDATE FOR PHOTODYNAMIC THERAPY

From a structurally distinct set of o-substituted tetraphenylporphyrin s, the picket fence porphyrin (PFP), 3,1-meso-tetrakis(o-propionamidop henyl)porphyrin (3,1-TPro) has been selected as a potential candidate for use in the photodynamic therapy (PDT) of cancer. In this report, t he time-dependent tissue distribution of C-14-labeled 3,1-TPro is desc ribed along with the results of various treatment regimens. The tissue distribution of radiolabeled 3,1-TPro is comparable to that of other porphyrin photosensitizers with the advantage of being most effective at 4 h and being cleared rapidly from most tissues. The results of the various treatment regimen experiments, as well as other studies, indi cate that the 3,1-TPro mechanism of action is similar to that of other photosensitizers, but may include some minor differences. The conclus ion is that 3,1-TPro and other PFP offer a class of effective photosen sitizers that may be exploited for their structural versatility, strai ghtforward synthesis leading to a compound of high purity and known st ructure, and stability (both in terms of shelf-life and in vivo metabo lism) as potential candidates for PDT.