Conjugation of Vancomycin with a Single Arginine Improves Efficacy against Mycobacteria by More Effective Peptidoglycan Targeting

Abstract

Drug resistant bacterial infections have emerged as one of the greatest threats to public health. The discovery and development of new antimicrobials and anti-infective strategies are urgently needed to address this challenge. Vancomycin is one of the most important antibiotics for the treatment of Gram-positive infections. Here, we introduce the vancomycin-arginine conjugate (V-R) as a highly effective antimicrobial against actively growing mycobacteria and difficult-to-treat mycobacterial biofilm populations. Further improvement in efficacy through combination treatment of V-R to inhibit peptidoglycan synthesis and ethambutol to inhibit arabinogalactan synthesis underscores the ability to identify compound synergies to more effectively target the Achilles heel of the cell-wall assembly. Moreover, we introduce mechanistic activity data and a molecular model derived from a d-Ala-d-Ala-bound vancomycin structure that we hypothesize underlies the molecular basis for the antibacterial improvement attributed to the arginine modification that is specific to peptidoglycan chemistry employed by mycobacteria and distinct from Gram-positive pathogens.

Engineered Vancomycin, with Increased Interactions with Peptidoglycan Stem Peptide, Conquers Non-tuberculosis Mycobacteria

“…9 Now, the same group show that V-R is also active against non-tuberculosis mycobacteria, and in some cases the MIC for V-R is 8 times lower than that of V against some NTMs. 4 The major highlight of this study, however, is not the demonstration that V-R is also active against NTM, but rather the mechanistic insight (other than enhanced membrane penetration) provided by the authors to account for the increased activity of V-R against Gram-negative bacteria and mycobacteria, vide infra.…”

“…In this issue of the Journal of Medicinal Chemistry, the groups of Wender and Cegelski at Stanford University reveal that when vancomycin (V), a glycopeptide antibiotic (see Figure 1 for structure), is conjugated to a single arginine (designated V-R, see Figure 2 for structure), it is highly effective at killing many NTM strains. 4 Of note, V-R is also able to disperse pre-established NTM biofilms. The Stanford team proposes that the enhanced activity of V-R over V in killing mycobacteria arises from an additional interaction between the arginine moiety in V-R and the mesodiaminopimelic acid (mDAP) residue, a constituent of the peptidoglycan (PG) stem peptide of mycobacteria and Gramnegative bacteria.…”

“…The Stanford team proposes that the enhanced activity of V-R over V in killing mycobacteria arises from an additional interaction between the arginine moiety in V-R and the mesodiaminopimelic acid (mDAP) residue, a constituent of the peptidoglycan (PG) stem peptide of mycobacteria and Gramnegative bacteria. 4 Vancomycin is a staple antibiotic that finds use in various bacterial infections, including methicillin-resistant Staphylococ-cus aureus and Clostridioides dif ficile infections. V inhibits cell wall synthesis via binding to the C-terminal D-Ala-D-Ala dipeptide of PG to inhibit peptidoglycan elongation and/or cross-linking.…”

“…For example, mycobacteria lack a true outer membrane but possess covalently linked mycolic acids that are interspersed with lipids and glycolipids to form the mycomembrane (akin to the Gram-negative outer membrane), which also presents a formidable challenge to penetration of antibiotics, including vancomycin. 4 The increasing rates of resistance to vancomycin, even among previously susceptible Gram-positive bacteria, led to sustained efforts to improve the activity of vancomycin, and many V analogs were developed (see Figure 1B for sites in V that have been modified). 6−8 A key feature of some of the V analogs with improved antibacterial properties, including approved drugs oritavancin, dalbavancin, and telavancin, is that the hydrophobic moieties help the compounds dimerize and anchor into the bacterial membrane to increase affinity for the PG target.…”

“…Both Gram-positive and Gram-negative bacteria contain PG stem peptide, but a major difference is that the third residue in most Gram-negative bacteria is mDAP, whereas in most Grampositive bacteria the third residue of the stem peptide is a lysine. 4 Interestingly, mDAP is also found in the Gram-positive Bacillus genus and mycobacteria. The Stanford team postulates that an enhanced binding to PG, via additional interactions with mDAP (see Figure 2), could explain the superior activity of V-R versus vancomycin in bacteria harboring mDAP in the PG stem peptide.…”