Biological Evaluation of Benzothiazole Ethyl Urea Inhibitors of Bacterial Type II Topoisomerases

Abstract

bThe type II topoisomerases DNA gyrase (GyrA/GyrB) and topoisomerase IV (ParC/ParE) are well-validated targets for antibacterial drug discovery. Because of their structural and functional homology, these enzymes are amenable to dual targeting by a single ligand. In this study, two novel benzothiazole ethyl urea-based small molecules, designated compound A and compound B, were evaluated for their biochemical, antibacterial, and pharmacokinetic properties. The two compounds inhibited the ATPase activity of GyrB and ParE with 50% inhibitory concentrations of <0.1 g/ml. Prevention of DNA supercoiling by DNA gyrase was also observed. Both compounds potently inhibited the growth of a range of bacterial organisms, including staphylococci, streptococci, enterococci, Clostridium difficile, and selected Gram-negative respiratory pathogens. MIC 90 s against clinical isolates ranged from 0.015 g/ml for Streptococcus pneumoniae to 0.25 g/ml for Staphylococcus aureus. No cross-resistance with common drug resistance phenotypes was observed. In addition, no synergistic or antagonistic interactions between compound A or compound B and other antibiotics, including the topoisomerase inhibitors novobiocin and levofloxacin, were detected in checkerboard experiments. The frequencies of spontaneous resistance for S. aureus were <2.3 ؋ 10 ؊10 with compound A and <5.8 ؋ 10؊11 with compound B at concentrations equivalent to 8؋ the MICs. These values indicate a multitargeting mechanism of action. The pharmacokinetic properties of both compounds were profiled in rats. Following intravenous administration, compound B showed approximately 3-fold improvement over compound A in terms of both clearance and the area under the concentration-time curve. The measured oral bioavailability of compound B was 47.7%.

An efficient synthesis and biological screening of benzofuran and benzo[ d ]isothiazole derivatives for Mycobacterium tuberculosis DNA GyrB inhibition

“…All the twenty eight compounds showed more than 75% of inhibition at 200 lM, and on further testing at concentrations of 100 and 50 lM, thirteen compounds was found to exhibit inhibition more than 60%. Further the compounds 11,12,13,14,15,19,26,30,31,32,33, 35 and 36 were tested at 25, 10, 5, 1 and 0.5 lM concentrations to calculate their IC 50 s. Compound 26 was found to be the most potent molecule with an IC 50 of 1.77 ± 0.14 lM. A dose dependent curve for 26 is shown in Figure 2.…”

“…Each of the compounds tested showed dose-dependent inhibition of the mycobacterial gyrase enzyme. DNA supercoiling inhibition studies were done at an initial concentration of 50 lM, and almost twenty compounds out of twenty eight (9,11,12,13,14,15,16,19,21,25,26,27,30,31,32,33,34,35,36 and 38) showed more than 70% inhibition as depicted in Table 1. Further these compounds were tested for their inhibitions at lower concentrations to obtain IC 50 , and the potent inhibitor 26 with good DNA GyrB inhibition also showed a better IC 50 of 0.42 ± 0.23 lM in the supercoiling assay, while the standard compound novobiocin showed 100% inhibition at 50 and 25 lM with an IC 50 of 46 ± 10 nM as illustrated in Figure 8.…”

“…Optimization of the structural classes was guided by two main criteria (i) to enhance hydrophobicity of the molecule so as to facilitate affinity toward the GyrB domain and (ii) to evaluate steric and electronic effects that could enhance the antimycobacterial potency. Chemical structure of previously reported synthetic inhibitors of DNA GyrB bearing a benzofuran core (1), 10 urea side chain (2-3) 11 were selected for the design of novel inhibitors through molecular hybridization (Series 1 and 2).…”

Dual targeting DNA gyrase B (GyrB) and topoisomerse IV (ParE) inhibitors: A review

“…14) as antibacterial agents. To improve the solubility and antimicrobial profile of compound 29, novel benzothiazole ethyl urea-based small molecules were synthesized by linking the carboxylate to the C-5 aryl group by a cyclic amine [78,79]. Both the antibacterial activity and the solubility increased.…”

Topoisomerases: Resistance versus Sensitivity, How Far We Can Go?

“…) have been tested for their antibacterial potential mediated by the inhibition of DNA gyrase/topoisomerase IV. Novel small molecules of benzothiazole ethyl urea have been observed to inhibit the growth of Clostridium difficile , streptococci, staphylococci, enterococci, and a few Gram‐negative respiratory pathogens . The pharmacophoric hybrids of urea and thiourea derivatives based on quinoline–aminopiperidine have recently been evaluated for M. tuberculosis GyrB inhibition and were shown to exhibit desirable minimal inhibitory concentration (MIC) values, a safe cytotoxic profile for eukaryotes and no cardiotoxicity in zebrafish .…”