Eravacycline

Members of the tetracycline class are frequently classified as bacteriostatic. However, recent findings have demonstrated an improved antibacterial killing profile, often achieving ≥3 log10 bacterial count reduction, when such antibiotics have been given for periods longer than 24 h. We aimed to study this effect with eravacycline, a novel fluorocycline, given in an immunocompetent murine thigh infection model over 72 h against two methicillin-resistant Staphylococcus aureus (MRSA) isolates (eravacycline MICs = 0.03 and 0.25 μg/ml) and three Enterobacteriaceae isolates (eravacycline MICs = 0.125 to 0.25 μg/ml). A humanized eravacycline regimen, 2.5 mg/kg of body weight given intravenously (i.v.) every 12 h (q12h), demonstrated progressively enhanced activity over the 72-h study period. A cumulative dose response in which bacterial density was reduced by more than 3 log10 CFU at 72 h was noted over the study period in the two Gram-positive isolates, and eravacycline performed similarly to comparator antibiotics (tigecycline, linezolid, and vancomycin). A cumulative dose response with eravacycline and comparators (tigecycline and meropenem) over the study period was also observed in the Gram-negative isolates, although more variability in bacterial killing was observed for all antibacterial agents.

After some years of stagnation there have been several new successful developments in the field of antibacterial agents. Most of these new developments have been in conventional antibacterial classes. New drugs among the beta-lactam agents are methicillin-resistant Staphylococcus aureus (MRSA) active cephalosporins (ceftaroline and ceftobiprole) and new combinations of beta-lactam with beta-lactamase inhibitors (ceftolozane/tazobactam, ceftazidime/avibactam, imipenem/relebactam and meropenem/RPX7009). New developments can also be observed among oxazolidinones (tedizolid, radezolid, cadazolid and MRX-I), macrolides/ketolides (modithromycin and solithromycin), aminoglycosides (plazomicin), quinolones (nemonoxacin, delafloxacin and avarofloxacin), tetracyclines (omadacycline and eravacycline) as well as among glycopeptides and lipopeptides (oritavancin, telavancin, dalbavancin and surotomycin). New agents in a very early developmental phase are FabI inhibitors, endolysines, peptidomimetics, lipid A inhibitors, methionyl-tRNA synthetase inhibitors and teixobactin.

Eravacycline is a novel, fully synthetic fluorocycline antibiotic of the tetracycline class being developed for the treatment of complicated urinary tract infections and complicated intra-abdominal infections. Eravacycline has activity against many key Gram-negative pathogens, including Enterobacteriaceae resistant to carbapenems, cephalosporins, fluoroquinolones and β-lactam/β-lactamase inhibitor combinations, including strains that are multidrug-resistant. Carbapenem-resistant Enterobacteriaceae (CRE) isolates from 2010 to 2013 (n=110) were characterized for carbapenemase genes by PCR and sequencing. MICs for eravacycline, tetracycline, tigecycline, amikacin, imipenem, ceftazidime, cefotaxime and levofloxacin were determined in broth microdilution assays. All isolates produced at least one carbapenemase, most frequently KPC-3. Nine isolates produced both a KPC serine carbapenemase and a metallo-β-lactamase, NDM-1 (n=1) or VIM-1 (n=8). The 110 isolates were highly resistant to all the β-lactams tested and to levofloxacin, and had MIC50/MIC90 values in the intermediate range for tetracycline and amikacin. MIC50/MIC90 values for eravacycline were 1/2 μg ml(-1) compared with 2/2 μg ml(-1) for tigecycline.