Discovery of dual GyrB/ParE inhibitors active against Gram-negative bacteria

New N-phenylpyrrolamide inhibitors of DNA gyrase with improved antibacterial activity

This study presents the discovery of a new series of N-phenylpyrrolamide inhibitors of bacterial DNA gyrase with improved antibacterial activity. The most potent inhibitors had low nanomolar IC50 values against Escherichia coli DNA gyrase (IC50; 2-20 nM) and E. coli topoisomerase IV (22i, IC50 = 143 nM). Importantly, none of the compounds showed activity against human DNA topoisomerase IIα, indicating selectivity for bacterial targets. Among the tested compounds, 22e emerged as the most effective against Gram-positive bacteria with minimum inhibitory concentration (MIC) values of 0.25 μg mL-1 against Staphylococcus aureus ATCC 29213 and MRSA, and 0.125 μg mL-1 against Enterococcus faecalis ATCC 29212. For Gram-negative bacteria, compounds 23b and 23c showed the greatest efficacy with MIC values ranging from 4 to 32 μg mL-1 against E. coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Acinetobacter baumannii ATCC 17978 and A. baumannii ATCC 19606. Notably, compound 23b showed promising activity against the clinically relevant Gram-negative pathogen Klebsiella pneumoniae ATCC 10031, with an MIC of 0.0625 μg mL-1. Furthermore, compounds 23a and 23c exhibited significantly lower susceptibility to resistance development compared to novobiocin in S. aureus ATCC 29213 and K. pneumoniae ATCC 10031. Overall, the most promising compounds of this series showed excellent on-target potency, marking a significant improvement over previous N-phenylpyrrolamide inhibitors.

Synthesis, biological evaluation and in silico studies of some new analogues of 3,5-vdisubstituted thiazolidin-2,4-dione

Background: A new series of 3,5-disubstituted thiazolidin-2,4-dione molecules were derived and characterized using various spectral techniques (1H NMR, IR, carbon, hydrogen, nitrogen, etc.) and physicochemical parameters. Materials & methods: The molecules were derived using Knoevenagel condensation followed by Mannich reaction and further synthesized analogues were screened for their antioxidant and antimicrobial potential using 2,2-diphenyl-1-picrylhydrazyl free radical scavenging method and serial tube dilution method, respectively, along with in silico studies (docking and absorption, distribution, metabolism and excretion parameters) to explore the drug-receptor interaction and druglikeness. Results & conclusion: In antimicrobial screening, the analogs MP2, MM6, MM7 and MM8 displayed promising activity while molecule MM4 exhibited better antioxidant potential in the series. In molecular docking analysis, the best-fitted analogs, namely, MM6 and MM7, showed good interactions.

Design, Synthesis, and Biological Evaluation of Novel Pyrimido[4,5-b]indole Derivatives Against Gram-Negative Multidrug-Resistant Pathogens

Due to the poor permeability across Gram-negative bacterial membranes and the troublesome bacterial efflux mechanism, only a few GyrB/ParE inhibitors with potent activity against Gram-negative pathogens have been reported. Among them, pyrimido[4,5-b]indole derivatives represented by GP-1 demonstrated excellent broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria but were limited by hERG inhibition and poor pharmacokinetics profile. To improve their drug-like properties, we designed a series of novel pyrimido[4,5-b]indole derivatives based on the tricyclic scaffold of GP-1 and the C-7 moiety of acorafloxacin. These efforts have culminated in the discovery of a promising compound 18r with reduced hERG liability and an improved PK profile. Compound 18r exhibited superior broad-spectrum in vitro antibacterial activity compared to GP-1, including a variety of clinical multidrug G^- pathogens, especially Acinetobacter baumannii, and the in vivo efficacy was also demonstrated in a neutropenic mouse thigh model of infection with multidrug-resistant A. baumannii.

Recent advances in antibacterial agents

Antimicrobial resistance is a global challenge and the effectiveness of old antibiotics is decreasing. Discovery and development of antibacterial agents have been accelerated to replenish the arsenal of antibiotics which is limited and shrinking. In recent years, significant advances have achieved in the antibacterial area, including new compounds of known classes and new compounds with new mechanisms. This review summarizes these advances and provides perspective on future directions of antibacterial agents.

Rational design of balanced dual-targeting antibiotics with limited resistance

Antibiotics that inhibit multiple bacterial targets offer a promising therapeutic strategy against resistance evolution, but developing such antibiotics is challenging. Here we demonstrate that a rational design of balanced multitargeting antibiotics is feasible by using a medicinal chemistry workflow. The resultant lead compounds, ULD1 and ULD2, belonging to a novel chemical class, almost equipotently inhibit bacterial DNA gyrase and topoisomerase IV complexes and interact with multiple evolutionary conserved amino acids in the ATP-binding pockets of their target proteins. ULD1 and ULD2 are excellently potent against a broad range of gram-positive bacteria. Notably, the efficacy of these compounds was tested against a broad panel of multidrug-resistant Staphylococcus aureus clinical strains. Antibiotics with clinical relevance against staphylococcal infections fail to inhibit a significant fraction of these isolates, whereas both ULD1 and ULD2 inhibit all of them (minimum inhibitory concentration [MIC] ≤1 μg/mL). Resistance mutations against these compounds are rare, have limited impact on compound susceptibility, and substantially reduce bacterial growth. Based on their efficacy and lack of toxicity demonstrated in murine infection models, these compounds could translate into new therapies against multidrug-resistant bacterial infections.

Discovery of Pyrido[2,3-b]indole Derivatives with Gram-Negative Activity Targeting Both DNA Gyrase and Topoisomerase IV

The rise of multidrug resistant (MDR) Gram-negative (GN) pathogens and the decline of available antibiotics that can effectively treat these severe infections are a major threat to modern medicine. Developing novel antibiotics against MDR GN pathogens is particularly difficult as compounds have to permeate the GN double membrane, which has very different physicochemical properties, and have to circumvent a plethora of resistance mechanisms such as multiple efflux pumps and target modifications. The bacterial type II topoisomerases DNA gyrase (GyrA₂B₂) and Topoisomerase IV (ParC₂E₂) are highly conserved targets across all bacterial species and validated in the clinic by the fluoroquinolones. Dual inhibitors targeting the ATPase domains (GyrB/ParE) of type II topoisomerases can overcome target-based fluoroquinolone resistance. However, few ATPase inhibitors are active against GN pathogens. In this study, we demonstrated a successful strategy to convert a 2-carboxamide substituted azaindole chemical scaffold with only Gram-positive (GP) activity into a novel series with also potent activity against a range of MDR GN pathogens. By systematically fine-tuning the many physicochemical properties, we identified lead compounds such as 17r with a balanced profile showing potent GN activity, high aqueous solubility, and desirable PK features. Moreover, we showed the bactericidal efficacy of 17r using a neutropenic mouse thigh infection model.