Photosensitization with derivatives of chlorin p6

Biophysical and photobiological properties of three derivatives of chlorin p6 were examined. These agents can be considered as lysyl analogs of the aspartyl chlorin NPe6. Lysyl chlorin p6 diester (LCP) and the triester analog (LCP2) were readily accumulated by murine leukemia L1210 cells, localized in lysosomes, and were relatively inefficient photosensitizing agents in vitro. In contrast, lysyl chlorin e6 imide (LCI) was poorly accumulated, concentrated in mitochondrial and plasma membranes, but was more efficacious. LCI was the most effective agent with regard to photosensitization of a murine tumor in vivo, but all three agents caused substantially more toxicity than was observed with NPe6.