Structure-activity relationship analyses to enhance the activity of antimicrobial peptides for selective therapeutic application

• Applicants: Dr. Daniel Friedrich; Professorin Dr. Ines Neundorf
• Subject Area: Pharmacy
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 575619215

Antimicrobial resistance represents a critical global health threat, particularly due to the rapid emergence of multidrug-resistant pathogens such as Neisseria gonorrhoeae and ESKAPE bacteria. The inefficacy of conventional antibiotics and the limited therapeutic pipeline underscore the urgent need for novel antimicrobial agents with high potency and selectivity. Antimicrobial peptides (AMPs) have emerged as promising candidates due to their unique membrane-disruptive mechanisms, which circumvent classical resistance pathways. However, clinical translation remains limited by challenges including low stability, insufficient selectivity, and proteolytic degradation. Building on our recent work, this project aims to develop and optimize novel AMPs with potent activity against N. gonorrhoeae by leveraging a structure-based design approach. We previously identified the cell-penetrating peptide sC18 as a promising scaffold and demonstrated that its antibacterial activity can be significantly enhanced through targeted amino acid substitutions and structural rigidification. A particularly active derivative, peptide 8A – derived from the truncated analog RL-8 and stabilized via a triazolyl bridge – showed remarkable potency, attributed to its preformed α-helical structure and distinct molecular surface properties. Using high-resolution NMR spectroscopy, we characterized these structural features and established a correlation between α-helical rigidity, surface charge distribution, and antimicrobial efficacy. The proposed project will extend this approach by systematically modifying the RL-8/8A peptide scaffold to generate a focused library of 40–50 analogs. Modifications will include incorporation of natural and unnatural amino acids to fine-tune hydrophobicity, charge distribution, and structural stability while preserving α-helical character through triazolyl-bridging or alternative stapling strategies. These analogs will be evaluated using a multidisciplinary pipeline combining solid- and solution-state NMR spectroscopy, antimicrobial activity assays, and biophysical membrane interaction studies. Three interconnected objectives will guide our work: (1) elucidating the molecular mechanism of membrane recognition by 8A and its variants; (2) enhancing antimicrobial potency through rational sequence modifications; and (3) increasing selectivity toward pathogenic bacteria, particularly N. gonorrhoeae, while minimizing cytotoxicity. Our iterative design-screen-optimize strategy will facilitate the identification of lead candidates with strong therapeutic potential. The collaborative effort between the Friedrich and Neundorf laboratories brings together complementary expertise in peptide synthesis, NMR-based structural biology, and cell biology. By integrating these strengths, this project seeks to advance the development of next-generation peptide antibiotics to treat gonorrhea, with broader implications for combating antimicrobial resistance.

• DFG Programme: Research Grants
• International Connection: Italy
• Co-Investigators: Professor Dr. Andreas Klatt; Professor Rasmus Linser, Ph.D.; Professorin Dr. Berenike Maier
• Cooperation Partners: Professorin Dr. Anna Maria Papini; Professor Dr. Paolo Rovero