5-aminolaevulinic acid peptide prodrugs enhance photosensitization for photodynamic therapy

L Bourre, F Giuntini, I M Eggleston, M Wilson, A J MacRobert

Research output: Contribution to journalArticle

31 Citations (Scopus)

Abstract

Intracellular porphyrin generation following administration of 5-aminolaevulinic acid (ALA) has been widely used in photodynamic therapy for a range of malignant and nonmalignant lesions. However, ALA is relatively hydrophilic and lacks stability at physiologic pH, limiting its bioavailability. We have investigated more lipophilic, uncharged ALA-peptide prodrugs based on phenylalanyl-ALA conjugates, which are water soluble and chemically stable for improving ALA delivery. Pharmacokinetics of the induced protoporphyrin IX (PpIX) were studied in transformed PAM212 keratinocyte cells and pig skin explants. The intracellular porphyrin production was substantially increased with Ac-L-Phe-ALA-Me (compound 1) and Ac-L-Phe-ALA (compound 3) compared with equimolar ALA: after 6-h incubation, the PpIX fluorescence measured using 0.01 mmol/L of compound 1 was enhanced by a factor of 5 compared with ALA. Phototoxicity results showed good correlation with PpIX levels, giving a LD50 (2.5 J/cm(2)) of 25 mu mol/L for ALA, 6 mu mol/L for 5-aminolaevulinic hexyl ester, and 2.6 mu mol/L for compound 1, which exhibited the highest phototoxicity. However, these results were stereospecific because the corresponding D-enantiomer, Ac-D-Phe-ALA-Me (compound 2), induced neither porphyrin synthesis nor phototoxicity. PpIX levels were considerably reduced when cells were incubated with compound 1 at low temperatures, consistent with active transport. In pig skin explants, compound 1 induced higher porphyrin fluorescence than ALA by a factor of 3. These results show that water-soluble peptide prodrugs of ALA can greatly increase its cellular uptake, generating more intracellular PpIX and improved tumor cell photosensitization. The derivatives are comparable in efficacy with 5-aminolaevulinic hexyl ester but less toxic and more stable at physiologic pH.
Original languageEnglish
Pages (from-to)1720-1729
Number of pages10
JournalMolecular Cancer Therapeutics
Volume7
Issue number6
DOIs
Publication statusPublished - 2008

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Photosensitivity Disorders
Aminolevulinic Acid
Photochemotherapy
Prodrugs
Peptides
Porphyrins
Phototoxic Dermatitis
Esters
Swine
Fluorescence
Skin
Water
Active Biological Transport
Poisons
Lethal Dose 50
Keratinocytes
Biological Availability

Cite this

5-aminolaevulinic acid peptide prodrugs enhance photosensitization for photodynamic therapy. / Bourre, L; Giuntini, F; Eggleston, I M; Wilson, M; MacRobert, A J.

In: Molecular Cancer Therapeutics, Vol. 7, No. 6, 2008, p. 1720-1729.

Research output: Contribution to journalArticle

Bourre, L ; Giuntini, F ; Eggleston, I M ; Wilson, M ; MacRobert, A J. / 5-aminolaevulinic acid peptide prodrugs enhance photosensitization for photodynamic therapy. In: Molecular Cancer Therapeutics. 2008 ; Vol. 7, No. 6. pp. 1720-1729.
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