Design, synthesis and evaluation of halogenated phenazine antibacterial prodrugs targeting nitroreductase enzymes for activation

Abstract

It is of great importance to develop new strategies to combat antibiotic resistance. Our lab has discovered halogenated phenazine (HP) analogues that are highly active against multidrug-resistant bacterial pathogens. Here, we report the design, synthesis, and study of a new series of nitroarene-based HP prodrugs that leverage intracellular nitroreductase (NTR) enzymes for activation and subsequent release of active HP agents. Our goals of developing HP prodrugs are to (1) mitigate off-target metal chelation (potential toxicity), (2) possess motifs to facilitate intracellular, bacterial-specific HP release, (3) improve water solubility, and (4) prevent undesirable metabolism (<i>e.g.</i>, glucuronidation of HP's phenol). Following the synthesis of HP-nitroarene prodrugs bearing a sulfonate ester linker, NTR-promoted release experiments demonstrated prodrug <b>HP-1-N</b> released 70.1% of parent <b>HP-1</b> after 16 hours (with only 6.8% <b>HP-1</b> release without NTR). In analogous <i>in vitro</i> experiments, no HP release was observed for control sulfonate ester compounds lacking the critical nitro group. When compared to parent HP compounds, nitroarene prodrugs evaluated during these studies demonstrate similar antibacterial activities in MIC and zone of inhibition assays (against lab strains and clinical isolates). In conclusion, HP-nitroarene prodrugs could provide a future avenue to develop potent agents that target antibiotic resistant bacteria.