Pharmacokinetics of EDP-420 after multiple oral doses in healthy adult volunteers and in a bioequivalence study

In vitro activities of the novel bicyclolides modithromycin (EDP-420, EP-013420, S-013420) and EDP-322 against MDR clinical Neisseria gonorrhoeae isolates and international reference strains

OBJECTIVES

New antimicrobials are essential to prevent gonorrhoea becoming an untreatable infection. Herein, the in vitro activities of the novel bicyclolides modithromycin (EDP-420, EP-013420, S-013420) and EDP-322 against Neisseria gonorrhoeae strains were investigated and compared with antimicrobials currently or previously recommended for treatment of gonorrhoea.

METHODS

MICs (mg/L) were determined using an agar dilution method (modithromycin and EDP-322) or Etest (seven antimicrobials) for a large geographically, temporally and genetically diverse collection of clinical N. gonorrhoeae isolates (n = 225) and international reference strains (n = 29), including diverse MDR and XDR isolates.

RESULTS

The MIC range, modal MIC, MIC50 and MIC90 of modithromycin and EDP-322 were 0.004-256, 0.25, 0.25 and 1 mg/L and 0.008-16, 0.5, 0.5 and 1 mg/L, respectively. The activities of modithromycin and EDP-322 were mainly superior to those of azithromycin and additional antimicrobials investigated. In general, there was no cross-resistance with other antimicrobials.

CONCLUSIONS

Modithromycin and EDP-322 exhibited high levels of in vitro activities against N. gonorrhoeae, including isolates resistant to azithromycin, cefixime, ceftriaxone, spectinomycin, ampicillin, tetracycline and ciprofloxacin. However, some cross-resistance with high-level azithromycin resistance (MIC = 4096 mg/L) was observed. Modithromycin and EDP-322 could be effective options for treatment of gonorrhoea, particularly for cases resistant to extended-spectrum cephalosporins and as a part of an antimicrobial combination therapy regimen. Nevertheless, it is important to detail the in vitro selection, in vivo emergence and mechanisms of resistance, pharmacokinetics/pharmacodynamics in humans and optimal dosing, and perform appropriate randomized controlled clinical trials.

Newer antibacterials in therapy and clinical trials

In order to deal with the rising problem of antibiotic resistance, newer antibacterials are being discovered and added to existing pool. Since the year 2000, however, only four new classes of antibacterials have been discovered. These include the oxazolidinones, glycolipopeptides, glycolipodepepsipeptide and pleuromutilins. Newer drugs were added to existing classes of antibiotics, such as streptogramins, quinolones, beta-lactam antibiotics, and macrolide-, tetracycline- and trimethoprim-related drugs. Most of the antibacterials are directed against resistant S. aureus infections, with very few against resistant gram-negative infections. The following article reviews the antibacterials approved by the FDA after the year 2000 as well as some of those in clinical trials. Data was obtained through a literature search via Pubmed and google as well as a detailed search of our library database.

New macrolide, lincosaminide and streptogramin B antibiotics

IMPORTANCE OF THE FIELD

New antibiotics are needed to overcome microbial resistance and to improve on the therapeutic index and clinical effectiveness of existing agents.

AREA COVERED IN THIS REVIEW

This review covers the journal and patent literature published from about the mid-2000s to 2010 to provide an overview of the large diversity of new chemical entities in the macrolide, lincosaminide and streptogramin B (MLS(B)) class.

WHAT THE READER WILL GAIN

The review identifies areas of the greatest effort and recent results in pursuing structure-activity relationships among MLS(B) antibiotics and highlights preclinical and clinical candidates that have arisen from these diverse discovery programs.

TAKE HOME MESSAGE

Research on the MLS(B) class appears promising for the eventual registration and commercialization of several new antibiotics that improve the clinical effectiveness of existing agents and combat antibiotic-resistant pathogens.

In vitro pharmacokinetic and pharmacodynamic evaluation of S-013420 against Haemophilus influenzae and Streptococcus pneumoniae

The pharmacokinetic (PK)/pharmacodynamic (PD) parameters and the antibacterial activity of S-013420, a novel bicyclolide, against Haemophilus influenzae and Streptococcus pneumoniae, including macrolide-resistant isolates, were investigated using an in vitro PD model. Various time-concentration curves were artificially constructed by modifying the PK data obtained in phase I studies. The activity against H. influenzae was evaluated using two parameters, that is, the area above the killing curve (AAC) and the viable cell reduction at 24 h. The relationships between the antibacterial activity of S-013420 and the three PK/PD parameters were investigated by fitting the data to the sigmoid maximum effective concentration model. The square of the correlation coefficient (R(2)) values for AAC versus the area under the concentration-time curve from 0 to 24 h (AUC(0-24))/MIC, the peak concentration (C(max))/MIC, and the cumulative percentage of a 24-h period that the drug concentration exceeded the MIC under steady-state PK conditions (%T(MIC)) were 0.92, 0.87, and 0.49, respectively. The R(2) values for viable cell reduction at 24 h versus AUC(0-24)/MIC, C(max)/MIC, and %T(MIC) were 0.93, 0.61, and 0.56, respectively. These results demonstrated that AUC(0-24)/MIC is the most significant parameter for evaluation of the antibacterial activity of S-013420. The values of AUC(0-24)/MIC required for maximum and static efficacy were 10.8 and 9.63, respectively, for H. influenzae and 16.3 to 22.3 and 4.66 to 9.01, respectively, for S. pneumoniae. This analysis is considered useful for determining the AUC value at the infection site, which would be required for efficacy in clinical use.