Alkoxyphenylthiazoles with broad-spectrum activity against multidrug-resistant gram-positive bacterial pathogens (original) (raw)
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ACS Infectious Diseases, 2019
Bacterial resistance to antibiotics is presently one of the most pressing healthcare challenges and necessitates discovering new antibacterials with unique chemical scaffolds. However, determining the optimal balance between structural requirements for pharmacological action and pharmacokinetic properties of novel antibacterial compounds is a significant challenge in drug development. The incorporation of lipophilic moieties within a compound's core structure can enhance biological activity but have a deleterious effect on drug-like properties. In this article, the lipophilicity of alkynylphenylthiazoles, previously identified as novel antibacterial agents, was reduced by introducing cyclic amines to the lipophilic side chain. In this regard, substitution with methylpiperidine (compounds 14-16) and thiomorpholine (compound 19) substituents significantly enhanced the aqueous solubility profile of the new compounds more than 150-fold compared to the first-generation lead compound 1b. Consequently, the pharmacokinetic profile of compound 15 was significantly enhanced with a notable improvement both in half-life and the time the compound's plasma concentration remained above its minimum inhibitory concentration (MIC) against methicillin-resistant Staphylococcus aureus (MRSA). In addition, compounds 14-16 and 19 were found to exert a bactericidal mode of action against MRSA and were not susceptible to resistance formation after 14 serial passages. Moreover, these compounds (at 2 × MIC) were superior to the antibiotic vancomycin in disrupting mature MRSA biofilm. The modifications to the alkynylphenylthiazoles reported herein successfully improved the pharmacokinetic profile of this new series while maintaining the compounds' biological activity against MRSA.
Journal of Medicinal Chemistry, 2019
The narrow antibacterial spectrum of phenylthiazole antibiotics was expanded by replacing the central thiazole with a pyrazole ring while maintaining its other pharmacophoric features. The most promising derivative, compound 23, was more potent than vancomycin against MDR-Grampositive clinical isolates, including vancomycin-and linezolid-resistant MRSA, with a minimum inhibitory concentration (MIC) value as low as 0.5 g/mL. Moreover, compound 23 was superior to imipenem and meropenem against highly pathogenic carbapenem-resistant strains, such as Acinetobacter baumannii, Klebsiella pneumoniae and E. coli. In addition to the notable biofilm inhibition activity, compound 23 outperformed both vancomycin and kanamycin in reducing the intracellular burden of both Gram-positive and Gram-negative pathogenic bacteria. Compound 23 cleared 90% of intracellular MRSA and 98% of Salmonella enteritidis at 2× the MIC. Moreover, preliminary pharmacokinetic investigations indicated that this class of novel antibacterial compounds is highly metabolically stable with a biological half-life of 10.5 hours suggesting a once-daily dosing regimen.
Methicillin-resistant Staphylococcus aureus infections are a significant global health challenge in part due to the emergence of strains exhibiting resistance to nearly all classes of antibiotics. This underscores the urgent need for the rapid development of novel antimicrobials to circumvent this burgeoning problem. Previously, whole-cell screening of a library of 2,5-disubstituted thiazole compounds revealed a lead compound exhibiting potent antimicrobial activity against MRSA. The present study, conducting a more rigorous analysis of the structureeactivity relationship of this compound, reveals a nonpolar, hydro-phobic functional group is favored at thiazole-C2 and an ethylidenehydrazine-1-carboximidamide moiety is necessary at C5 for the compound to possess activity against MRSA. Furthermore, the MTS assay confirmed analogs 5, 22d, and 25 exhibited an improved toxicity profile (not toxic up to 40 mg/mL to mammalian cells) over the lead 1. Analysis with human liver microsomes revealed compound 5 was more metabolically stable compared to the lead compound (greater than eight-fold improvement in the half-life in human liver microsomes). Collectively the results presented demonstrate the novel thiazole derivatives synthesized warrant further exploration for potential use as future antimicrobial agents for the treatment of multidrug-resistant S. aureus infections.
In Vitro Antimicrobial Activity of New Substituted Phenylthiazole Derivatives
Iranian Journal of Toxicology, 2018
Background: In this study, we evaluated antibacterial and antifungle activity of these derivatives against gram positive (Staphylococcus aureus, Bacillus subtilis, B. cereus), gram negative (Proteus vulgaris) bacteria and fungale (Candida albicans, C. tropicalis and C. glabrata). Methods: The broth macro dilution and well agar diffusion methods were used for determination of inhibition zoom (IZ) and minimum inhibitory concentration (MIC) during preliminary evaluation of antimicrobial activity. Results: The (MIC) values of tested compounds revealed that all compounds were active against Staphylococcus oureus and exhibited the same antibacterial activity in comparison to ceftizoxim (MIC=125µg/mL). The results of antifungal screening showed that all the compounds were potent antimicrobial activity against tested pathogenic fungi (MIC=250 to1000 µg/ml). Compounds (6a) and (6b) showed the maximum activity with MIC value of 250 µg/ml against all tested fungi, but compound (6h) showed poor antifungal activity against all fungi. MIC values for title compounds were similar to MIC results for fluconazol. Conclusions: All the compounds are potent antifungal and antibacterial activity against tested microorganism.
Second-Generation Phenylthiazole Antibiotics with Enhanced Pharmacokinetic Properties
Journal of Medicinal Chemistry, 2016
A series of second-generation analogues for 2-(1-(2-(4-butylphenyl)-4-methylthiazol-5-yl)ethylidene)aminoguanidine (1) have been synthesized and tested against methicillin-resistant Staphylococcus aureus (MRSA). The compounds were designed with the objective of improving pharmacokinetic properties. This main aim has been accomplished by replacing the rapidly hydrolyzable Schiff-base moiety of first-generation members with a cyclic, unhydrolyzable pyrimidine ring. The hydrazide-containing analogue 17 was identified as the most potent analogue constructed thus far. The corresponding amine 8 was 8 times less active. Finally, incorporating the nitrogenous side chain within an aromatic system completely abolished the antibacterial character. Replacement of the n-butyl group with cyclic bioisosteres revealed cyclohexenyl analogue 29, which showed significant improvement in in vitro anti-MRSA potency. Increasing or decreasing the ring size deteriorated the antibacterial activity. Compound 17 demonstrated a superior in vitro and in vivo pharmacokinetic profile, providing compelling evidence that this particular analogue is a good drug candidate worthy of further analysis.
Methicillin-and vancomycin-resistant Staphylococcus aureus (MRSA and VRSA) infections are growing global health concerns. Structure−activity relationships of phenylthiazoles as a new antimicrobial class have been addressed. We present 10 thiazole derivatives that exhibit strong activity against 18 clinical strains of MRSA and VRSA with acceptable PK profile. Three derivatives revealed an advantage over vancomycin by rapidly eliminating MRSA growth within 6 h, and no derivatives are toxic to HeLa cells at 11 μg/mL. Figure 1. Chemical structures of lead 1a and 4b (removal of the cationic moiety) and 1b (removal of the lipophilic alkane side chain).
European journal of medicinal chemistry, 2017
The promising antibacterial potency of arylthiazole antibiotics is offset by their limited activity against intracellular bacteria (namely methicillin-resistant Staphylococcus aureus (MRSA)), similar to many clinically-approved antibiotics. The failure to target these hidden pathogens is due to the compounds' lack of proper characteristics to accumulate intracellularly. Fine tuning of the size and polar-surface-area of the linking heteroaromatic ring provided a new series of 5-thiazolylarylthiazoles with balanced properties that allow them to sufficiently cross and accumulate inside macrophages infected with MRSA. The most promising compound 4i exhibited rapid bactericidal activity, good metabolic stability and produced over 80% reduction of intracellular MRSA in infected macrophages.
Antibiotics
The growing antimicrobial resistance to last-line antimicrobials among Gram-positive pathogens remains a major healthcare emergency worldwide. Therefore, the search for new small molecules targeting multidrug-resistant pathogens remains of great importance. In this paper, we report the synthesis and in vitro antimicrobial activity characterisation of novel thiazole derivatives using representative Gram-negative and Gram-positive strains, including tedizolid/linezolid-resistant S. aureus, as well as emerging fungal pathogens. The 4-substituted thiazoles 3h, and 3j with naphthoquinone-fused thiazole derivative 7 with excellent activity against methicillin and tedizolid/linezolid-resistant S. aureus. Moreover, compounds 3h, 3j and 7 showed favourable activity against vancomycin-resistant E. faecium. Compounds 9f and 14f showed broad-spectrum antifungal activity against drug-resistant Candida strains, while ester 8f showed good activity against Candida auris which was greater than fluco...
Journal of medicinal chemistry, 2017
The emergence of antibiotic-resistant bacterial species, such as vancomycin-resistant enterococci (VRE), necessitates the development of new antimicrobials. Here, we investigate the spectrum of antibacterial activity of three phenylthiazole-substituted aminoguanidines. These compounds possess potent activity against VRE, inhibiting growth of clinical isolates at concentrations as low as 0.5 μg/mL. The compounds exerted a rapid bactericidal effect, targeting cell wall synthesis. Transposon mutagenesis suggested three possible targets: YubA, YubB (undecaprenyl diphosphate phosphatase (UPPP)), and YubD. Both UPPP as well as undecaprenyl diphosphate synthase were inhibited by compound 1. YubA and YubD are annotated as transporters and may also be targets because 1 collapsed the proton motive force in membrane vesicles. Using Caenorhabditis elegans, we demonstrate that two compounds (1, 3, at 20 μg/mL) retain potent activity in vivo, significantly reducing the burden of VRE in infected w...