Assessing Cutibacterium Acnes Susceptibility With Clindamycin Phosphate 1.2%/Adapalene 0.15%/Benzoyl Peroxide 3.1% Gel Use: Six-Month Analysis.

BACKGROUND: The only approved triple-combination acne treatment – clindamycin phosphate 1.2%/adapalene 0.15%/benzoyl peroxide 3.1% (CAB) gel - demonstrated efficacy/safety in 12-week clinical trials. However, real-world treatment may require 6 months for maximum benefits in some cases. Since long-term antibiotic use can lead to resistance in the causative Cutibacterium acnes (C. acnes), this analysis evaluated the effect of long-term CAB use on C. acnes.

METHODS: Pooled data from 2 identical, 24-week, single-center, open-label studies evaluated once-daily CAB in participants aged ≥12 years with moderate/severe acne (Investigator's Global Assessment [IGA] of 3/4). Plates inoculated with central forehead swabs were monitored for C. acnes colony formation. Clindamycin susceptibility was assessed via minimum inhibitory concentration (MIC) values using Epsilometer tests; MIC ≥8 μg/mL indicated resistance.

RESULTS: Of 50 participants enrolled, 45 completed the studies. At baseline, C. acnes strains were isolated from 82% (37/45) of participants. After 24 weeks, CAB-treated participants with cultivable isolates decreased by nearly half to 44% (20/45). For susceptible strains isolated at week 24, MIC values remained low (mean, 0.19 μg/mL). Only 1 participant without growth at baseline had cultivable C. acnes at week 24, deemed clindamycin-susceptible. Only the 5 participants (11%) with resistant C. acnes isolates at baseline had resistant isolates at study end, though all 5 had acne improvements at week 24 (IGA decrease, 1-3 points; lesion reductions, 40%-100%).

CONCLUSIONS: Long-term CAB gel treatment did not lead to antibiotic resistance development and was efficacious in participants with resistant isolates at baseline, suggesting CAB is well suited for long-term acne treatment.