Novel Mercapto Propionamide Derivatives with Potent New Delhi Metallo-ß-Lactamase-1 Inhibitory Activity and Low Toxicity.

The emergence and worldwide prevalence of New Delhi metallo-ß-lactamase 1 (NDM-1) expressing Gram-negative bacteria with resistance against most ß-lactam antibiotics pose a serious threat to human health. However, no NDM-1 inhibitors are clinically approved at present. Herein, based on the lead compound captopril, a series of compounds were designed, synthesized, and evaluated for NDM-1 inhibitory activities. All designed compounds showed single digit micromolar or submicromolar NDM-1 inhibitory activities, which were much more potent than that of captopril. Among them, compounds 14a and 14m exhibited excellent NDM-1 inhibitory activities, with IC50 values of 0.10 and 0.12 µM, respectively. Further studies demonstrated that compound 14m displayed low cytotoxicity, good water solubility, high metabolic stability, and low acute toxicity in mice. Importantly, compound 14m exhibited potent synergistic antimicrobial activities with Meropenem (MEM) for the treatment of clinically isolated NDM-1-expressing strains.

Dithiocarbamates: Efficient metallo-ß-lactamase inhibitors with good antibacterial activity when combined with meropenem.

The activity of ß-lactam antibiotics is compromised by metallo-ß-lactamases (MBLs). Herein, a series of dithiocarbamate derivatives were designed and synthesized. Their antibacterial activities were tested in combination with meropenem (MEM) against several MBL (NDM and IMP type)-producing clinical isolates. Clinical isolates harboring NDM-1 and IMP-4 became susceptible to MEM when it was combined with dithiocarbamate compounds 4a, 4b or 4f synthesized in this work. Compounds 4a and 4b increased the effectiveness of MEM by up to 2560 times against strains. In vitro bactericidal dynamics tests showed that bacteria died within 24 h when they were treated with compound 4f + MEM. Compounds 4a, 4b and 4f were non-hemolytic and exhibited low toxicity toward HeLa cells in vitro. These data show that compounds containing dithiocarbamate functional group may be helpful in the development of MBL inhibitors.

Phenylboronic Acid Derivatives as Validated Leads Active in Clinical Strains Overexpressing KPC-2: A Step against Bacterial Resistance.

The emergence and dissemination of multidrug resistant (MDR) pathogens resistant to nearly all available antibiotics poses a significant threat in clinical therapy. Among them, Klebsiella pneumoniae clinical isolates overexpressing KPC-2 carbapenemase are the most worrisome, extending bacterial resistance to last-resort carbapenems. In this study, we investigate the molecular recognition requirements in the KPC-2 active site by small phenylboronic acid derivatives. Four new phenylboronic acid derivatives were designed and tested against KPC-2. For the most active, despite their simple chemical structures, nanomolar affinity was achieved. The new derivatives restored susceptibility to meropenem in clinical strains overexpressing KPC-2. Moreover, no cytotoxicity was detected in cell-viability assays, which further validated the designed leads. Two crystallographic binary complexes of the best inhibitors binding KPC-2 were obtained at high resolution. Kinetic descriptions of slow binding, time-dependent inhibition, and interaction geometries in KPC-2 were fully investigated. This study will ultimately lead toward the optimization and development of more-effective KPC-2 inhibitors.

ETX2514 is a broad-spectrum ß-lactamase inhibitor for the treatment of drug-resistant Gram-negative bacteria including Acinetobacter baumannii.

Multidrug-resistant (MDR) bacterial infections are a serious threat to public health. Among the most alarming resistance trends is the rapid rise in the number and diversity of ß-lactamases, enzymes that inactivate ß-lactams, a class of antibiotics that has been a therapeutic mainstay for decades. Although several new ß-lactamase inhibitors have been approved or are in clinical trials, their spectra of activity do not address MDR pathogens such as Acinetobacter baumannii. This report describes the rational design and characterization of expanded-spectrum serine ß-lactamase inhibitors that potently inhibit clinically relevant class A, C and D ß-lactamases and penicillin-binding proteins, resulting in intrinsic antibacterial activity against Enterobacteriaceae and restoration of ß-lactam activity in a broad range of MDR Gram-negative pathogens. One of the most promising combinations is sulbactam-ETX2514, whose potent antibacterial activity, in vivo efficacy against MDR A. baumannii infections and promising preclinical safety demonstrate its potential to address this significant unmet medical need.

Discovery of 1-Hydroxypyridine-2(1H)-thione-6-carboxylic Acid as a First-in-Class Low-Cytotoxic Nanomolar Metallo ß-Lactamase Inhibitor.

VIM-2 is one of the most common carbapenem-hydrolyzing metallo ß-lactamases (MBL) found in many drug-resistant Gram-negative bacterial strains. Currently, there is a lack of effective lead compounds with optimal therapeutic potential within our drug development pipeline. Here we report the discovery of 1-hydroxypyridine-2(1H)-thione-6-carboxylic acid (3) as a first-in-class metallo ß-lactamase inhibitor (MBLi) with a potent inhibition Ki of 13 nm against VIM-2 that corresponds to a remarkable 0.99 ligand efficiency. We further established that 3 can restore the antibiotic activity of amoxicillin against VIM-2-producing E. coli in a whole cell assay with an EC50 of 110 nm. The potential mode of binding of 3 from molecular modeling provided structural insights that could corroborate the observed changes in the biochemical activities. Finally, 3 possesses a low cytotoxicity (CC50 ) of 97 µm with a corresponding therapeutic index of 880, making it a promising lead candidate for further optimization in combination antibacterial therapy.