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In Vitro Activity of Gepotidacin (GSK2140944) against Neisseria gonorrhoeae.

ABSTRACT: Gepotidacin (formerly GSK2140944) is a novel, first-in-class, triazaacenaphthylene antibacterial that inhibits bacterial DNA gyrase and topoisomerase IV via a unique mechanism and has demonstrated in vitro activity against Neisseria gonorrhoeae, including drug-resistant strains, and also targets pathogens associated with other conventional and biothreat infections. Broth microdilution was used to evaluate the MIC and minimum bactericidal concentration (MBC) activity of gepotidacin and comparators against 25 N. gonorrhoeae strains (including five ciprofloxacin-nonsusceptible strains). Gepotidacin activity was also evaluated against three N. gonorrhoeae strains (including a ciprofloxacin-nonsusceptible strain) for resistance development, against three N. gonorrhoeae strains (including two tetracycline- and azithromycin-nonsusceptible strains) using time-kill kinetics and checkerboard methods, and against two N. gonorrhoeae strains for the investigation of postantibiotic (PAE) and subinhibitory (PAE-SME) effects. The MIC50 and MIC90 for gepotidacin against the 25 N. gonorrhoeae isolates tested were 0.12 and 0.25 μg/ml, respectively. The MBC50 and MBC90 for gepotidacin were 0.25 and 0.5 μg/ml, respectively. Gepotidacin was bactericidal, and single-step resistance selection studies did not recover any mutants, indicating a low rate of spontaneous single-step resistance. For combinations of gepotidacin and comparators tested using checkerboard methods, there were no instances where antagonism occurred and only one instance of synergy (with moxifloxacin; fractional inhibitory concentration, 0.375). This was not confirmed by in vitro time-kill studies. The PAE for gepotidacin against the wild-type strain ranged from 0.5 to >2.5 h, and the PAE-SME was >2.5 h. These in vitro data indicate that further study of gepotidacin is warranted for potential use in treating infections caused by N. gonorrhoeae.

SUBMITTER: Farrell DJ

PROVIDER: S-EPMC5328517 | biostudies-other | 2017 Mar

REPOSITORIES: biostudies-other

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Project description:Neisseria gonorrhoeae deploys a unique immune evasion strategy wherein the lacto-N-neotetraose termini of lipooligosaccharide (LOS) are "capped" by a surface LOS sialyltransferase (Lst), using extracellular host-derived CMP-sialic acid (CMP-Neu5Ac in humans). LOS sialylation enhances complement resistance by recruiting factor H (FH; alternative complement pathway inhibitor) and also by limiting classical pathway activation. Sialylated LOS also engages inhibitory Siglecs on host leukocytes, dampening innate immunity. Previously, we showed that analogues of CMP-sialic acids (CMP-nonulosonates [CMP-NulOs]), such as CMP-Leg5,7Ac2 and CMP-Neu5Ac9N3, are also substrates for Lst. Incorporation of Leg5,7Ac2 and Neu5Ac9N3 into LOS results in N. gonorrhoeae being fully serum sensitive. Importantly, intravaginal administration of CMP-Leg5,7Ac2 attenuated N. gonorrhoeae colonization of mouse vaginas. In this study, we characterize and develop additional candidate therapeutic CMP-NulOs. CMP-ketodeoxynonulosonate (CMP-Kdn) and CMP-Kdn7N3, but not CMP-Neu4,5Ac2, were substrates for Lst, further elucidating gonococcal Lst specificity. Lacto-N-neotetraose LOS capped with Kdn and Kdn7N3 bound FH to levels ∼60% of that seen with Neu5Ac and enabled gonococci to resist low (3.3%) but not higher (10%) concentrations of human complement. CMP-Kdn, CMP-Neu5Ac9N3, and CMP-Leg5,7Ac2 administered intravaginally (10 μg/d) to N. gonorrhoeae-colonized mice were equally efficacious. Of the three CMP-NulOs above, CMP-Leg5,7Ac2 was the most pH and temperature stable. In addition, Leg5,7Ac2-fed human cells did not display this NulO on their surface. Moreover, CMP-Leg5,7Ac2 was efficacious against several multidrug-resistant gonococci in mice with a humanized sialome (Cmah-/- mice) or humanized complement system (FH/C4b-binding protein transgenic mice). CMP-Leg5,7Ac2 and CMP-Kdn remain viable leads as topical preventive/therapeutic agents against the global threat of multidrug-resistant N. gonorrhoeae.

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In Vitro Activity of Gepotidacin (GSK2140944) against Neisseria gonorrhoeae.

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