Interactions between Zoliflodacin and Neisseria gonorrhoeae Gyrase and Topoisomerase IV: Enzymological Basis for Cellular Targeting.

Gyrase and topoisomerase IV are the cellular targets for fluoroquinolones, a critically important class of antibacterial agents used to treat a broad spectrum of human infections. Unfortunately, the clinical efficacy of the fluoroquinolones has been curtailed by the emergence of target-mediated resistance. This is especially true for Neisseria gonorrhoeae, the causative pathogen of the sexually transmitted infection gonorrhea. Spiropyrimidinetriones (SPTs), a new class of antibacterials, were developed to combat the growing antibacterial resistance crisis. Zoliflodacin is the most clinically advanced SPT and displays efficacy against uncomplicated urogenital gonorrhea in human trials. Like fluoroquinolones, the primary target of zoliflodacin in N. gonorrhoeae is gyrase, and topoisomerase IV is a secondary target. Because unbalanced gyrase/topoisomerase IV targeting has facilitated the evolution of fluoroquinolone-resistant bacteria, it is important to understand the underlying basis for the differential targeting of zoliflodacin in N. gonorrhoeae. Therefore, we assessed the effects of this SPT on the catalytic and DNA cleavage activities of N. gonorrhoeae gyrase and topoisomerase IV. In all reactions examined, zoliflodacin displayed higher potency against gyrase than topoisomerase IV. Moreover, zoliflodacin generated more DNA cleavage and formed more stable enzyme-cleaved DNA-SPT complexes with gyrase. The SPT also maintained higher activity against fluoroquinolone-resistant gyrase than topoisomerase IV. Finally, when compared to zoliflodacin, the novel SPT H3D-005722 induced more balanced double-stranded DNA cleavage with gyrase and topoisomerase IV from N. gonorrhoeae, Escherichia coli, and Bacillus anthracis. This finding suggests that further development of the SPT class could yield compounds with a more balanced targeting against clinically important bacterial infections.

Management of Neisseria gonorrhoeae infection: from drug resistance to drug repurposing.

INTRODUCTION: Neisseria gonorrhoeae is a common sexually transmitted disease connected with extensive drug resistance to many antibiotics. Presently, only expanded spectrum cephalosporins (ceftriaxone and cefixime) and azithromycin remain useful for its management. AREAS COVERED: New chemotypes for the classical antibiotic drug target gyrase/topoisomerase IV afforded inhibitors with potent binding to these enzymes, with an inhibition mechanism distinct from that of fluoroquinolones, and thus less prone to mutations. The α-carbonic anhydrase from the genome of this bacterium (NgCAα) was also validated as an antibacterial target. EXPERT OPINION: By exploiting different subunits from the gyrase/topoisomerase IV as well as new chemotypes, two new antibiotics reached Phase II/III clinical trials, zoliflodacin and gepotidacin. They possess a novel inhibition mechanism, binding in distinct parts of the enzyme compared to the fluoroquinolones. Other chemotypes with inhibitory activity in these enzymes were also reported. NgCAα inhibitors belonging to a variety of classes were obtained, with several sulfonamides showing MIC values in the range of 0.25-4 µg/mL and significant activity in animal models of this infection. Acetazolamide and similar CA inhibitors might thus be repurposed as antiinfectives. The scientific/patent literature has been searched for on PubMed, ScienceDirect, Espacenet, and PatentGuru, from 2016 to 2024.

Evaluating the potency of zoliflodacin against Helicobacter pylori: In vitro activity and conserved GyrB target.

BACKGROUND: The current standard treatment for Helicobacter pylori infection, which involves a combination of two broad-spectrum antibiotics, faces significant challenges due to its detrimental impact on the gut microbiota and the emergence of drug-resistant strains. This underscores the urgent requirement for the development of novel anti-H. pylori drugs. Zoliflodacin, a novel bacterial gyrase inhibitor, is currently undergoing global phase III clinical trials for treating uncomplicated Neisseria gonorrhoeae. However, there is no available data regarding its activity against H. pylori. MATERIALS AND METHODS: We evaluated the in vitro activity of zoliflodacin against H. pylori clinical isolates (n = 123) with diverse multidrug resistance. We performed DNA gyrase supercoiling and microscale thermophoresis assays to identify the target of zoliflodacin in H. pylori. We analyzed 2262 H. pylori whole genome sequences to identify Asp424Asn and Lys445Asn mutations in DNA gyrase subunit B (GyrB) that are associated with zoliflodacin resistance. RESULTS: Zoliflodacin exhibits potent activity against all tested isolates, with minimal inhibitory concentration (MIC) values ranging from 0.008 to 1 µg/mL (MIC50: 0.125 µg/mL; MIC90: 0.25 µg/mL). Importantly, there was no evidence of cross-resistance to any of the four first-line antibiotics commonly used against H. pylori. We identified GyrB as the primary target of zoliflodacin, with Asp424Asn or Lys445Asn substitutions conferring resistance. Screening of 2262 available H. pylori genomes for the two mutations revealed only one clinical isolate carrying Asp424Asn substitution. CONCLUSION: These findings support the potential of zoliflodacin as a promising candidate for H. pylori treatment, warranting further development and evaluation.

Neisseria gonorrhoeae Antimicrobial Resistance: The Future of Antibiotic Therapy.

The growing threat of antibiotic-resistant Neisseria gonorrhoeae, which causes gonorrhea, presents a current public health challenge. Over the years, the pathogen has developed resistance to different antibiotics, leaving few effective treatment options. High-level resistance to key drugs, including ceftriaxone, has become a concerning reality. This article primarily focuses on the treatment of gonorrhea and the current clinical trials aimed at providing new antibiotic treatment options. We explore ongoing efforts to assess new antibiotics, including zoliflodacin, and gepotidacin. These drugs offer new effective treatment options, but their rapid availability remains uncertain. We delve into two ongoing clinical trials: one evaluating the efficacy and safety of gepotidacin compared to the standard ceftriaxone-azithromycin combination and the other assessing the non-inferiority of zoliflodacin versus the combination therapy of ceftriaxone-azithromycin. These trials represent crucial steps in the search for alternative treatments for uncomplicated gonorrhea. Notably, gonorrhea has been included in the "WHO Priority Pathogens List for Research and Development of New Antibiotics". In conclusion, the urgent need for innovative treatment strategies is underscored by the rising threat of antibiotic resistance in N. gonorrhoeae; collaboration among researchers, industries, and healthcare authorities is therefore essential.

Pharmacodynamics of zoliflodacin plus doxycycline combination therapy against Neisseria gonorrhoeae in a gonococcal hollow-fiber infection model.

Antimicrobial resistance in the sexually transmitted bacterium Neisseria gonorrhoeae is compromising the management and control of gonorrhea globally. Optimized use and enhanced stewardship of current antimicrobials and development of novel antimicrobials are imperative. The first in class zoliflodacin (spiropyrimidinetrione, DNA Gyrase B inhibitor) is a promising novel antimicrobial in late-stage clinical development for gonorrhea treatment, i.e., the phase III randomized controlled clinical trial (ClinicalTrials.gov Identifier: NCT03959527) was recently finalized, and zoliflodacin showed non-inferiority compared to the recommended ceftriaxone plus azithromycin dual therapy. Doxycycline, the first-line treatment for chlamydia and empiric treatment for non-gonococcal urethritis, will be frequently given together with zoliflodacin because gonorrhea and chlamydia coinfections are common. In a previous static in vitro study, it was indicated that doxycycline/tetracycline inhibited the gonococcal killing of zoliflodacin in 6-h time-kill curve analysis. In this study, our dynamic in vitro hollow-fiber infection model (HFIM) was used to investigate combination therapies with zoliflodacin and doxycycline. Dose-range experiments using the three gonococcal strains WHO F (susceptible to relevant therapeutic antimicrobials), WHO X (extensively drug-resistant, including ceftriaxone-resistant; zoliflodacin-susceptible), and SE600/18 (zoliflodacin-susceptible strain with GyrB S467N substitution) were conducted simulating combination therapy with a single oral dose of zoliflodacin 0.5-4 g combined with a doxycycline daily oral dose of 200 mg administered as 100 mg twice a day, for 7 days (standard dose for chlamydia treatment). Comparing combination therapy of zoliflodacin (0.5-4 g single dose) plus doxycycline (200 mg divided into 100 mg twice a day orally, for 7 days) to zoliflodacin monotherapy (0.5-4 g single dose) showed that combination therapy was slightly more effective than monotherapy in the killing of N. gonorrhoeae and suppressing emergence of zoliflodacin resistance. Accordingly, WHO F was eradicated by only 0.5 g single dose of zoliflodacin in combination with doxycycline, and WHO X and SE600/18 were both eradicated by a 2 g single dose of zoliflodacin in combination with doxycycline; no zoliflodacin-resistant populations occurred during the 7-day experiment when using this zoliflodacin dose. When using suboptimal (0.5-1 g) zoliflodacin doses together with doxycycline, gonococcal mutants with increased zoliflodacin MICs, due to GyrB D429N and the novel GyrB T472P, emerged, but both the mutants had an impaired biofitness. The present study shows the high efficacy of zoliflodacin plus doxycycline combination therapy using a dynamic HFIM that more accurately and comprehensively simulate gonococcal infection and their treatment, i.e., compared to static in vitro models, such as short-time checkerboard experiments or time-kill curve analysis. Based on our dynamic in vitro HFIM work, zoliflodacin plus doxycycline for the treatment of both gonorrhea and chlamydia can be an effective combination.