Recent Advances in the Exploration of Therapeutic Analogues of Gramicidin S, an Old but Still Potent Antimicrobial Peptide.

Gramicidin S (GS), one of the oldest commercially used peptide antibiotics, is known for its robust antibacterial activity against both Gram-positive and Gram-negative bacterial strains. Although it was discovered well over 70 years ago, its clinical potential was limited to topical applications because of its high hemolytic activity. To overcome this side effect, significant efforts have been invested in the chase for GS analogues with high therapeutic index (e.g., high antimicrobial activity and low hemolytic activity) in the past decades. In this Perspective, the structural properties and biological profiles (including the recently discovered activities) of representative GS analogues designed by different approaches are described and analyzed. We also present how the general structure-activity relationships were established and how they could help in the design of more efficient GS analogues.