Ribonucleotide reductase, a novel target for gonorrhea

Antibiotic resistant Neisseria gonorrhoeae (Ng) are an emerging public health threat due to increasing numbers of multidrug resistant (MDR) organisms. We identified two novel orally active inhibitors, PTC-847 and PTC-672, that exhibit a narrow spectrum of activity against Ng including MDR isolates. By selecting organisms resistant to the novel inhibitors and sequencing their genomes, we identified a new therapeutic target, the class Ia ribonucleotide reductase (RNR). Activity studies and negative stain electron microscopy of the Ng Ia RNR suggest that these inhibitors potentiate conversion of its active α ₂ β ₂ state to an inactive α ₄ β ₄ similar to states first identified with the Escherichia coli (Ec) Ia RNR. Resistance mutations in Ng map to the N -terminal, ATP cone domain of its α subunit and disrupt the interaction with the β subunit required to form the specific quaternary inhibited state. Oral administration of PTC-672 reduces Ng infection in a mouse model and may have therapeutic potential for treatment of Ng that is resistant to current drugs.