An LL-37-Derived Peptide in Gel Form Killed MRSA on Human Skin

Researchers tested peptide P10 in four pharmaceutical ointment bases: hypromellose gel, Softisan-containing cream, Cetomacrogol cream, and Cetomacrogol cream with Vaseline. Chemical stability and antibacterial activity were assessed over 16 months at 4°C. Efficacy was tested on Leiden human epidermal models (LEMs) — lab-grown human skin equivalents — colonized with MRSA, including biofilm formation. Additional testing was performed on ex-vivo human skin samples. Toxicity to skin tissue was assessed for each formulation.

MRSA infections are a growing global health crisis, and skin is one of the most common sites of infection. Current topical antibiotics like mupirocin face increasing resistance. Antimicrobial peptides derived from LL-37 offer a new approach because bacteria find it much harder to develop resistance to peptides that disrupt their membranes. This study demonstrates a complete preclinical package — stability, efficacy against both planktonic bacteria and biofilms, human skin compatibility, and an optimized formulation — bringing P10 closer to clinical development.

LL-37 is the only cathelicidin antimicrobial peptide in humans, and researchers have been engineering derivatives of it for therapeutic use. P10 represents an optimized fragment that retains antibacterial potency while being more practical to manufacture. This study is part of the broader effort to develop peptide-based alternatives to conventional antibiotics, particularly for topical applications where drug-resistant bacteria like MRSA are most problematic. The formulation work is especially important — many antimicrobial peptides lose activity in certain bases, making the stability data in hypromellose gel particularly valuable.

Testing was performed on lab-grown skin models and ex-vivo skin, not in living patients. The antibacterial activity was assessed against a single MRSA strain; broader testing against diverse clinical isolates would strengthen the findings. No clinical trial data exists yet for P10. The requirement for refrigerated storage (4°C) may limit practical use in some settings. Cost of peptide synthesis for commercial production was not addressed.