Proline-regulated G5P2 antimicrobial peptide achieves 93.52% bacterial clearance in vivo, synergizes with antibiotics

The escalating crisis of antibiotic resistance poses a severe global health threat, necessitating the urgent discovery of novel antimicrobial agents. Traditional antibiotics are increasingly ineffective against multidrug-resistant (MDR) bacterial pathogens, driving a critical need for new therapeutic strategies. Antimicrobial peptides (AMPs) represent a promising alternative due to their distinct, often membrane-disrupting, mechanisms of action, which can circumvent established resistance pathways. However, the rational design and efficient screening of AMPs that balance potent efficacy with high selectivity and low toxicity remain significant challenges in drug discovery.

Researchers designed a universal palindromic sequence template, G(LK)n(KL)nG-NH2 (designated GnPm), to systematically explore the impact of secondary structure on antimicrobial activity. This template allowed for varying numbers of LK/KL repeats (n = 2-6) and the uniform insertion of 0 to 3 proline residues (m = 0-3) in the middle region to regulate peptide secondary structures. Peptides were synthesized and screened for antibacterial activity and their ability to disrupt bacterial membranes. The optimized peptide, G5P2, was further evaluated for its potential to induce bacterial drug resistance, its synergistic effects with traditional antibiotics, and its in vivo antibacterial efficacy and safety in an animal model.

Both the number of LK/KL repeats and the presence of proline residues were confirmed to effectively regulate the secondary structure of the GnPm peptides, directly influencing their antibacterial activity. The optimized peptide, G5P2, exhibited potent antibacterial activity primarily through a typical membrane-disrupting mechanism. Importantly, G5P2 was not prone to inducing bacterial drug resistance, a critical advantage over conventional antibiotics. Furthermore, it demonstrated significant synergy with traditional antibiotics, effectively delaying the emergence of antibiotic resistance when used in combination. > In an in vivo model, G5P2 achieved an impressive 93.52% bacterial clearance, underscoring its robust efficacy. The peptide also showed a high safety profile, with an LD50 of 89.87 mg/kg, indicating a wide therapeutic window. These findings highlight G5P2 as a promising candidate molecule and validate the proline-regulation strategy for developing new antimicrobial agents.