Photodynamic therapy (PDT) is a promising new methodology for the treatment of cancer. PDT has mostly involved the intravenous administration of photosensitizing agents (porphyrins and structurally related compounds) which tend to be preferentially accumulated by malignant tissues . A novel approach to PDT involves endogenous photosensitization by administration of 5-aminolevulinic acid (ALA) which is converted by the heme biosynthesis pathway to protoporphyrin IX, an efficient photosensitizer . Although ALA-PDT has proved very successful clinically for certain applications , problems have arisen in treating deeper tumors where ALA applied topically may not penetrate sufficiently deeply. Attempts to solve this problem are currently being made by the use of alkylesters of ALA rather than ALA itself . The use of these esters is however limited by their toxicity at the high concentrations that must be injected to compensate for the lack of selectivity. In this poster, we wish to report the synthesis and use of new ALA derivatives which are able to release free ALA more selectively. ALA-PEG-esters (PEG = polyethylenglycol) appeared to be potentially less toxic ALA-esters leading to the production of PpIX in cells. Moreover, a promising use of ALA-ester-peptide derivatives is described .
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