The efficacy and tolerability of 5-aminolevulinic acid 5% thermosetting gel photodynamic therapy (PDT) in the treatment of mild-to-moderate acne vulgaris. A two-center, prospective assessor-blinded, proof-of-concept study

Background: Acne vulgaris is a chronic inflammatory skin disease, commonly treated with topical or systemic drugs, according to the severity of the condition. Retinoids and antibiotic compounds are considered cornerstone approaches in this condition. However, low adherence to the therapy and the issue of bacterial resistance undermine the efficacy in the long term. Photodynamic therapy (PDT) with 20% aminolevulinic acid (ALA) has shown to be effective in the treatment of inflammatory acne. Skin tolerability, however, could be a limiting factor for a widespread use of this approach. A new formulation of 5% ALA in thermosetting gel has been recently available. This formulation allows a more convenient application procedure without occlusion and better and more efficient release of the active compound in comparison with traditional ALA formulations like creams or ointments. Study aim: To evaluate in a two-center, assessor-blinded, prospective, proof-of-concept study, the efficacy, and tolerability of red-light (630 nm) PDT with a new 5-ALA "low-dose" topical gel formulation (5%) in the treatment of inflammatory mild-to-moderate acne vulgaris (AV). Subjects and methods: A total of 35 subjects with moderate AV of the face (mean age: 24 ± 8 years, 13 men and 22 women) were enrolled, after their written informed consent. The primary outcome was the evolution of GAG (Global Acne Grade System) score at baseline and after an average of three, 630-nm, 15-minute, PDT sessions, performed every 2 weeks. GAG score was also calculated in a follow-up visit 6 months after the last PDT session. Skin tolerability was assessed during PDT sessions with a patient-reported discomfort level evaluation score from 0 (no discomfort at all) to 3 (severe discomfort). Results: At baseline, the GAG score was 21 ± 6. After the last PDT session, the GAG score evaluated in a blinded fashion (digital photographs) was significantly reduced to 6.5 ± 5.7, representing a 70% reduction (P = .0001, Wilcoxon test; mean difference 14.9; 95% CI of the difference: 12.1-17.6). At the follow-up visit, the GAG score was 6.7 ± 6.8. The 5% ALA thermosetting gel Red-light PDT was in general very well tolerated with a discomfort mean level score of 0.5 ± 1. Conclusion: This proof-of-concept study supports the efficacy of 5% ALA thermosetting gel red-light PDT in inflammatory acne of the face with a relevant clinical improvement of inflammatory lesions with a very good tolerability profile. Clinical improvement was maintained in the medium term (Trial Registration Number: ISRCTN66066651).