Following topical application, 5-aminolaevulinic acid (ALA) is metabolised to protoporphyrin IX, a photosensitiser for photodynamic therapy (PDT). This compound accumulates intracellularly in the treated actinic keratosis lesions where it is activated by illumination with red light of a suitable wavelength and energy. This triggers the formation of reactive oxygen species which cause damage to cellular components and eventually destroy the target cells.1
The efficacy and tolerability of ALA (78mg/g gel) was compared with that of methyl-5-aminolaevulinate (MAL, 160mg/g cream) or placebo in a randomised, observer-blind study involving 571 adults with 4–8 mild to moderate actinic keratosis lesions on the face or scalp. Patients underwent one PDT session, repeated once after 12 weeks if residual lesions remained.1,2
ALA was superior to both placebo and MAL in terms of the primary endpoint, complete patient clearance 12 weeks after the last PDT (78.2% versus 17.1% [p<0.0001] and 64.2% [p<0.05], respectively). In addition, lesion complete clearance rates were greater for ALA than for placebo or MAL (90.4% versus 37.1% and 83.2%, respectively).1,2
In a double-blind study of similar design (n=122), ALA was significantly more effective than placebo in terms of complete patient clearance rates (64% versus 11%; p<0.0001) and lesion complete clearance rates (81% versus 22%) 12 weeks after the last PDT.3
Efficacy and tolerability dependent on light source
In both studies, significant differences in efficacy rates and adverse event profiles were observed for the two light sources, in favour of narrow spectrum sources for efficacy and broad spectrum sources for tolerability.1-3
- Ameluz Summary of Product Characteristics, December 2011
- Dirschka T et al. Br J Dermatol 2012; 166: 137-46.
- Szeimies R-M et al. Br J Dermatol 2010; 163: 386-94.
Further information: Spirit Healthcare