Affiliation:
1. Vertex Pharmaceuticals Incorporated, 130 Waverly St., Cambridge, Massachusetts 02139
Abstract
ABSTRACT
A structure-guided drug design approach was used to optimize a novel series of aminobenzimidazoles that inhibit the essential ATPase activities of bacterial DNA gyrase and topoisomerase IV and that show potent activities against a variety of bacterial pathogens. Two such compounds, VRT-125853 and VRT-752586, were characterized for their target specificities and preferences in bacteria. In metabolite incorporation assays, VRT-125853 inhibited both DNA and RNA synthesis but had little effect on protein synthesis. Both compounds inhibited the maintenance of negative supercoils in plasmid DNA in
Escherichia coli
at the MIC. Sequencing of DNA corresponding to the GyrB and ParE ATP-binding regions in VRT-125853- and VRT-752586-resistant mutants revealed that their primary target in
Staphylococcus aureus
and
Haemophilus influenzae
was GyrB, whereas in
Streptococcus pneumoniae
it was ParE. In
Enterococcus faecalis
, the primary target of VRT-125853 was ParE, whereas for VRT-752586 it was GyrB. DNA transformation experiments with
H. influenzae
and
S. aureus
proved that the mutations observed in
gyrB
resulted in decreased susceptibilities to both compounds. Novobiocin resistance-conferring mutations in
S. aureus
,
H. influenzae
, and
S. pneumoniae
were found in
gyrB
, and these mutants showed little or no cross-resistance to VRT-125853 or VRT-752586 and vice versa. Furthermore,
gyrB
and
parE
double mutations increased the MICs of VRT-125853 and VRT-752586 significantly, providing evidence of dual targeting. Spontaneous frequencies of resistance to VRT-752586 were below detectable levels (<5.2 × 10
−10
) for wild-type
E. faecalis
but were significantly elevated for strains containing single and double target-based mutations, demonstrating that dual targeting confers low levels of resistance emergence and the maintenance of susceptibility in vitro.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Pharmacology (medical),Pharmacology
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