Discovery of a novel antifungal agent: All‐hydrocarbon stapling modification of peptide Aurein1.2

Abstract

Aurein1.2 is secreted by the Australian tree frog Litoria aurea and is active against a broad range of infectious microbes including bacteria, fungi, and viruses. Its antifungal potency has garnered considerable interest in developing novel classes of natural antifungal agents to fight pathogenic infection by fungi. However, serious pharmacological hurdles remain, hindering its clinical translation. To alleviate its susceptibility to proteolytic degradation and improve its antifungal activity, six conformationally locked peptides were synthesized through hydrocarbon stapling modification and evaluated for their physicochemical and antifungal parameters. Among them, SAU2‐4 exhibited significant improvement in helicity levels, protease resistance, and antifungal activity compared to the template linear peptide Aurein1.2. These results confirmed the prominent role of hydrocarbon stapling modification in the manipulation of peptide pharmacological properties and enhanced the application potential of Aurein1.2 in the field of antifungal agent development.

Exploring biocompatible chemistry to create stapled and photoswitchable variants of the antimicrobial peptide aurein 1.2

“…This substitution pattern replaced the two negatively charged aspartate and glutamate residues (increasing the net charge to +3), a stapling pattern that had previously proven successful in enhancing the antifungal activity of aurein 1.2. 20 Positions 4 and 11 used for stapling of peptide 2 were also found to be least important for antimicrobial activity in an alanine scanning of aurein 1.2. 52 Interestingly, both peptides exhibited reduced helicity compared to the wildtype aurein 1.2 at 25% TFE (as shown in Table 1 and Figure 1).…”

“…This contrasts with recent investigations involving all-hydrocarbon staples, which resulted in increased helicity for the same stapling pattern as in 2, however, with a different net charge due to acetylation of the N-terminus. 20 Peptide 1 displayed reduced solubility, which might be related to its overall low helicity observed in the CD experiments (Figure 1B).…”

“…Previous studies with aurein 1.2 used all-hydrocarbon stapling in i, i + 4 and i, i + 7. 19,20 We designed four stapled analogues of aurein 1.2, compounds 1-4 (Table 1), exploring classical i, i + 7 and unconventional i, i + 8 stapling patterns. We further included two bicyclic aurein 1.2 derivatives, 5 and 6 (Table 1), which were previously published, for comparison.…”

“…Notably, the stapling pattern in peptide 2 has previously been reported to inhibit various Candida species with MICs as low as 4-8 μg/ml. 20 Therefore, peptide 2 might also be a promising antifungal agent, which may be the focus of a future study.…”

“…Stabilising the active conformation may result in higher biological activity but, importantly, also improves proteolytic stability and membrane permeability. Both magainin 2 17,18 and aurein 1.2 19,20 were previously stapled to improve their properties. While all these studies used all‐hydrocarbon stapling, 21 we have recently developed an alternative biocompatible stapling strategy that relies on the unique reactivity of cyanopyridine and 1,2‐aminothiols, which can be used for one‐ and two‐component peptide stapling and (bi)cyclisation 22–25 .…”