De Novo Design of Mirror-Image Dimeric Antimicrobial Peptides with Low Drug Resistance and In Vivo Efficacy.

Dimerization and mirror-image modification are effective strategies for enhancing the antimicrobial activity and stability of antimicrobial peptides (AMPs). However, mirror-image dimeric AMPs, characterized by their mirror-image amino acid sequences and mirror-image stereocenters within a single peptide, have been rarely reported. In this study, 19 mirror-image dimeric AMPs and 2 all d-/l-type AMPs are designed and synthesized to investigate their structure-activity relationships. Peptides with YYYXXxxyyy or yyyxxXXYYY sequences (X/Y represents cationic/hydrophobic residues, x/y denotes d-type residues) possess favorable bacterial selectivity. The superior peptide M-WL-D/L exhibits potent activity against multidrug-resistant bacteria, a low propensity for drug resistance, favorable stability, robust membrane disruption, high DNA affinity, and immunoregulatory activity. Notably, M-WL-D/L demonstrates in vivo half-lives of 22.4 min (5 mg/kg) and 20.7 min (10 mg/kg), along with effective in vivo efficacy and satisfactory safety. This innovative AMP design strategy, with M-WL-D/L as a standout candidate, offers a promising avenue for combating multidrug-resistant bacteria.