Background Acne vulgaris(AV) is the eighth most prevalent disease worldwide and affects pilosebaceous units with the multifactorial pathogensis. Antibiotics are considered first-line therapy in the management of moderate to severe acne. However, currently available agents may be associated with adverse effects (AEs), their prolonged usage potentially leading to antibiotic resistance ,which may occur in Cutibacterium acnes (C. acnes), and limit the efficacy of antibiotics for the treatment of AV. These limitations demonstrate a need for antibacterial agents for acne with improved safety profiles and a targeted, well-tolerated. An antimicrobial peptide(AMP) called GDP20 is novel , topical bactericidal against C. acnes and has an anti-inflammatory effect for the treatment of acne .   Objectives To evaluate the anti-C.acnes activity of twice-daily GDP20 with help of MALDI NOF method.     Material and method Twelve subjects with mild to moderate acne were enrolled into this pilot study. All subjects were under dermatologic care and were maintained on their acne agents throughout the study. Patients applied to the bacteriological analysis by method of matrix-assisted laser desorption/ionization Time Of Flight (MALDI-TOF) mass spectrometry at two weeks intervals. The results were documented at baseline and after visits and evaluated for clinical improvement and C. acnes growth.   Results After 2 weeks of topical therapy with GDP20 in 41.7% (5/12) subjects having excellent results, 33.3% (4/12) with good results, 25% (3/12) with fair results. All subjects with mild to moderate severity of acne was marked by clinical remission. No serious AEs occurred. The levels of C.acnes contamination before and after GDP20 application are presented in Fig 1. Fig 1. Comparison of the number of C.acne before and after treatment of Acne patients     Conclusions

The application of topical agents GDP20 in this pilot study appeared to demonstrate a reduction in C.acnes growth and remarkable effect on acne manifestation. These results indicate the possibility to use GDP20 as a possible substitute for widespectrum antibiotics due to known bacterial antibiotic resistance.