| abstract |
Lipophilic and amphiphilic therapeutic or diagnostic agents having water solubilizing groups attached thereto by bonds that can be cleaved readily by one or more of the various proteases that are active in the extracellular fluid or on the surfaces of cells in many types of malignant tissue may accumulate selectively in such malignant tissues. Protease mediated removal of the water solubilizing groups converts such drugs into lipophilic or amphiphilic forms which are more soluble in plasma membrane lipids and which therefore enter cells more readily. Since the extracellular fluid in most non-malignant tissues under normal circumstances has little such protease activity, removal of the water solubilizing groups takes place primarily within malignant tissues, with consequent preferential accumulation of the lipophilic or amphiphilic forms of the drug within malignant tissues. Certain lipophilic and amphiphilic porphyrins and chlorins may be modified by the addition of water solubilizing groups, such as alcohols, which are attached by short polypeptide chains, that are stable while in the circulation but are cleaved by proteases in malignant tissue to provide novel compounds useful for the photodynamic therapy of cancer. |