Site-Specific Antimicrobial Activity of a Dual-Responsive Ciprofloxacin Prodrug

Abstract

Bacterial infections create distinctive microenvironments with a unique mix of metabolites and enzymes compared with healthy tissues that can be used to trigger the activation of antibiotic prodrugs. Here, a single and dual prodrug masking the C3 carboxylate and C7 piperazine of the fluoroquinolone, ciprofloxacin, responsive to nitroreductase (NTR) and/or hydrogen sulfide (H₂S), was developed. Masking both functional groups reduced the activity of the prodrug against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i>, increasing its minimum inhibitory concentration (MIC) by ∼512-fold (<i>S. aureus</i>) and ∼8000-fold (<i>E. coli</i> strains), while masking a single group only increased the MIC by ∼128-fold. Bacteria subjected to prolonged prodrug exposure did not show any increase in resistance. Triggering assays demonstrated the conversion of prodrugs to ciprofloxacin, and in a murine infection model, responsive prodrugs showed antibacterial activity comparable to that of ciprofloxacin, suggesting <i>in vivo</i> activation of prodrugs. Thus, the potential for site-specific antibiotic treatment with reduced threat of resistance is demonstrated.