In vitro activities of ABT-492, a new fluoroquinolone, against 155 aerobic and 171 anaerobic pathogens isolated from antral sinus puncture specimens from patients with sinusitis

In vitro activity of delafloxacin against anaerobic bacteria compared with other antimicrobials

The aim of this study was to describe the in vitro activity of delafloxacin against 230 anaerobic isolates and compare it with the activity of other antimicrobials used against infections caused by anaerobic microorganisms. Minimal inhibitory concentrations (MICs) were lower for delafloxacin than for all other antibiotics tested with the exception of piperacillin-tazobactam and meropenem against Gram-positive anaerobic cocci. Only two (0.8 %) isolates of Bacteroides spp. showed a MIC ≥4 μg/mL. With some exceptions, the present results show lower MICs for delafloxacin in comparison to the other antibiotics used against anaerobes.

Delafloxacin for the treatment of adult patients with community-acquired bacterial pneumonia

INTRODUCTION

Delafloxacin is a novel fluoroquinolone with peculiar characteristics such as a weak acid character, frequent in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA), and a low potential for resistance selection compared with other fluoroquinolones.

AREAS COVERED

The present narrative review summarizes the available data on the use of delafloxacin for the treatment of community-acquired bacterial pneumonia (CABP).

EXPERT OPINION

Delafloxacin is a novel fluoroquinolone with a unique profile and some interesting characteristics for the treatment of CABP, such as its marked activity against gram-positive bacteria, including MRSA, the possible use as monotherapy (owing to anti-Gram-negative and anti-atypical bacteria activity), the retained activity against many Gram-positive organisms resistant to other fluoroquinolones, and the availability of both oral and intravenous formulations. The results of the DEFINE-CABP phase-3 randomized controlled trial have shown noninferiority of delafloxacin vs. moxifloxacin for the treatment of CABP, thereby providing a further option for this indication. Against this background, future post-marketing experiences remain of crucial importance for further refining the place in therapy of delafloxacin in the real-life management algorithms of CABP, either as first-line option or step-down/outpatient treatment.

Emerging drugs for treating methicillin-resistant Staphylococcus aureus

Introduction: In clinical practice, methicillin-resistant Staphylococcus aureus (MRSA) represents a major threat and has been associated with high rates of inadequate antibiotic treatment and significant increases in morbidity, mortality, and overall healthcare costs. The association between the prescription of an inappropriate or delayed antibiotic and impaired clinical outcomes has been widely described. Areas covered: To address the threat of MRSA, many new therapeutic options with a peculiar activity against MRSA have been recently developed and approved. New agents are characterized by specific issues in terms of spectrum of activity, pharmacokinetics, risk of drug-drug interactions, and toxicity, with potential advantages that should be considered in everyday clinical practice. Expert opinion: The most attractive characteristic of new drugs is represented by the broad spectrum of activity against multidrug-resistant pathogens; moreover, new compounds in most cases are characterized by favorable toxicity profiles compared with old drugs currently used in clinical practice. Some of the new antimicrobials will be also available as oral formulations, with the potential for oral switch, even in infections due to resistant pathogens. In particular conditions/populations (e.g. liver failure, renal disease, pregnancy, diabetic, children, and elderly), novel antibiotics with reduced toxicity could be an important option, including after hospital discharge.

Clinical review of delafloxacin: a novel anionic fluoroquinolone

Delafloxacin is a novel anionic fluoroquinolone (FQ) approved for treatment of acute bacterial skin and skin structure infections (ABSSSIs) caused by a number of Gram-positive and Gram-negative organisms including MRSA and Pseudomonas aeruginosa. The unique chemical structure of delafloxacin renders it a weak acid and results in increased potency in acidic environments. In Phase III studies, delafloxacin had similar outcomes to comparator regimens for treatment of ABSSSIs, and was well tolerated overall. Similar to other FQs, delafloxacin is available in both intravenous and oral formulations, but differs in that delafloxacin exerts a minimal effect on cytochrome P450 enzymes and on the corrected QT interval. This novel FQ has the potential to be utilized across a wide variety of clinical settings; however, post-marketing surveillance and long-term safety and resistance data will be essential to identify optimal use scenarios.

New Antibiotics for Pneumonia

Delayed antimicrobial prescriptions and inappropriate treatment can lead to poor outcomes in pneumonia. In nosocomial infections, especially in countries reporting high rates of antimicrobial resistance, the presence of multidrug-resistant gram-negative and gam-positive bacteria can limit options for adequate antimicrobial treatment. New antibiotics, belonging to known classes of antimicrobials or characterized by novel mechanisms of actions, have recently been approved or are under development. Advantages of the new compounds include enhanced spectrum of activity against resistant bacteria, high lung penetration, good tolerability, and possibility for intravenous to oral sequential therapy. This article reviews characteristics of newly approved and investigational compounds.

What Is Old Is New Again: Delafloxacin, a Modern Fluoroquinolone

Delafloxacin is a new fluoroquinolone antimicrobial approved for the treatment of acute bacterial skin and skin structure infections (ABSSSIs) in adults using dosage regimens of 300 mg intravenously every 12 hours, 450 mg orally every 12 hours, or switching from intravenous to oral regimens for a 5- to 14-day treatment duration. Dosage adjustments in patients with severe renal dysfunction (estimated glomerular filtration rate [eGFR] = 15-29 ml/min/1.73 m² ) are not required for oral doses but should be decreased to 200 mg intravenously every 12 hours in patients requiring parenteral therapy. Due to insufficient data, use of delafloxacin is not recommended for patients on hemodialysis or with end-stage renal disease (eGFR < 15 ml/min/1.73 m² ). Delafloxacin works through inhibition of DNA gyrase (topoisomerase II) and topoisomerase IV, which are essential enzymes for bacterial DNA transcription, replication, repair, and recombination and exhibits bactericidal activity against gram-positive and gram-negative organisms through a concentration-dependent matter. Delafloxacin has a very broad spectrum of activity against atypical, anaerobic, and resistant gram-negative and gram-positive bacteria, including methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa. During phase 3 trials, the most common side effects associated with delafloxacin were gastrointestinal (nausea, diarrhea). Unlike other fluoroquinolones, there does not seem to be a risk of QTc prolongation or phototoxicity with delafloxacin. The availability of both parenteral and oral formulations for delafloxacin distinguishes it from many of the currently available agents approved for ABSSSIs. Phase 3 studies for the treatment of respiratory infections are currently under way, and future results of these studies will further help delineate the role of delafloxacin.

In Vitro Activity of Delafloxacin and Microbiological Response against Fluoroquinolone-Susceptible and Nonsusceptible Staphylococcus aureus Isolates from Two Phase 3 Studies of Acute Bacterial Skin and Skin Structure Infections

Delafloxacin is an investigational anionic fluoroquinolone antibiotic with broad-spectrum in vitro activity, including activity against Gram-positive organisms, Gram-negative organisms, atypical organisms, and anaerobes. The in vitro activity of delafloxacin and the percent microbiological response in subjects infected with fluoroquinolone-susceptible and nonsusceptible Staphylococcus aureus isolates were determined from two global phase 3 studies of delafloxacin versus vancomycin plus aztreonam in patients with acute bacterial skin and skin structure infections (ABSSSI). Patients from 23 countries, predominately the United States but also Europe, South America, and Asia, were enrolled. The microbiological intent-to-treat (MITT) population included 1,042 patients from which 685 S. aureus isolates were submitted for identification and susceptibility testing per CLSI guidelines at the central laboratory (JMI Laboratories, North Liberty, IA). The comparator fluoroquinolone antibiotics included levofloxacin and ciprofloxacin. Nonsusceptibility to these antibiotics was determined using CLSI breakpoints. S. aureus isolates were 33.7% levofloxacin nonsusceptible (LVX-NS). The delafloxacin MIC₉₀ values against levofloxacin-nonsusceptible S. aureus, methicillin-resistant S. aureus (MRSA), and methicillin-susceptible S. aureus isolates were all 0.25 μg/ml. Delafloxacin demonstrated high rates of microbiological response against LVX-NS isolates as well as isolates with documented mutations in the quinolone resistance-determining region (QRDR). S. aureus was eradicated or presumed eradicated in 98.4% (245/249) of delafloxacin-treated patients. Similar eradication rates were observed for delafloxacin-treated subjects with levofloxacin-nonsusceptible S. aureus isolates (80/81; 98.8%) and MRSA isolates (70/71; 98.6%). Microbiological response rates of 98.6% were observed with delafloxacin-treated subjects with S. aureus isolates with the S84L mutation in gyrA and the S80Y mutation in parC, the most commonly observed mutations in global phase 3 studies. The data suggest that delafloxacin could be a good option for the treatment of infections caused by S. aureus isolates causing ABSSSI, including MRSA isolates, where high rates of ciprofloxacin and levofloxacin nonsusceptibility are observed. (The phase 3 studies described in this paper have been registered at ClinicalTrials.gov under identifiers NCT01984684 and NCT01811732.).

In Vitro Activity of Delafloxacin and Microbiological Response against Fluoroquinolone-Susceptible and Nonsusceptible Staphylococcus aureus Isolates from Two Phase 3 Studies of Acute Bacterial Skin and Skin Structure Infections

Delafloxacin is an investigational anionic fluoroquinolone antibiotic with broad-spectrum in vitro activity, including activity against Gram-positive organisms, Gram-negative organisms, atypical organisms, and anaerobes. The in vitro activity of delafloxacin and the percent microbiological response in subjects infected with fluoroquinolone-susceptible and nonsusceptible Staphylococcus aureus isolates were determined from two global phase 3 studies of delafloxacin versus vancomycin plus aztreonam in patients with acute bacterial skin and skin structure infections (ABSSSI). Patients from 23 countries, predominately the United States but also Europe, South America, and Asia, were enrolled. The microbiological intent-to-treat (MITT) population included 1,042 patients from which 685 S. aureus isolates were submitted for identification and susceptibility testing per CLSI guidelines at the central laboratory (JMI Laboratories, North Liberty, IA). The comparator fluoroquinolone antibiotics included levofloxacin and ciprofloxacin. Nonsusceptibility to these antibiotics was determined using CLSI breakpoints. S. aureus isolates were 33.7% levofloxacin nonsusceptible (LVX-NS). The delafloxacin MIC₉₀ values against levofloxacin-nonsusceptible S. aureus, methicillin-resistant S. aureus (MRSA), and methicillin-susceptible S. aureus isolates were all 0.25 μg/ml. Delafloxacin demonstrated high rates of microbiological response against LVX-NS isolates as well as isolates with documented mutations in the quinolone resistance-determining region (QRDR). S. aureus was eradicated or presumed eradicated in 98.4% (245/249) of delafloxacin-treated patients. Similar eradication rates were observed for delafloxacin-treated subjects with levofloxacin-nonsusceptible S. aureus isolates (80/81; 98.8%) and MRSA isolates (70/71; 98.6%). Microbiological response rates of 98.6% were observed with delafloxacin-treated subjects with S. aureus isolates with the S84L mutation in gyrA and the S80Y mutation in parC, the most commonly observed mutations in global phase 3 studies. The data suggest that delafloxacin could be a good option for the treatment of infections caused by S. aureus isolates causing ABSSSI, including MRSA isolates, where high rates of ciprofloxacin and levofloxacin nonsusceptibility are observed. (The phase 3 studies described in this paper have been registered at ClinicalTrials.gov under identifiers NCT01984684 and NCT01811732.)

In Vitro Activity of Delafloxacin against Contemporary Bacterial Pathogens from the United States and Europe, 2014

The in vitro activities of delafloxacin and comparator antimicrobial agents against 6,485 bacterial isolates collected from medical centers in Europe and the United States in 2014 were tested. Delafloxacin was the most potent agent tested against methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus, Streptococcus pneumoniae, viridans group streptococci, and beta-hemolytic streptococci and had activity similar to that of ciprofloxacin and levofloxacin against certain members of the Enterobacteriaceae. Overall, the broadest coverage of the tested pathogens (Gram-positive cocci and Gram-negative bacilli) was observed with meropenem and tigecycline in both Europe and the United States. Delafloxacin was shown to be active against organisms that may be encountered in acute bacterial skin and skin structure infections, respiratory infections, and urinary tract infections.

Delafloxacin: design, development and potential place in therapy

Delafloxacin (DLX) is a new fluoroquinolone pending approval, which has shown a good in vitro and in vivo activity against major pathogens associated with skin and soft tissue infections and community-acquired respiratory tract infections. DLX also shows good activity against a broad spectrum of microorganisms, including those resistant to other fluoroquinolones, as methicillin-resistant Staphylococcus aureus. Its pharmacokinetic properties and excellent activity in acidic environments make DLX an alternative in the treatment of these and other infections. In this manuscript, a detailed analysis of this new fluoroquinolone is performed, from its chemical structure to its in vivo activity in recently published clinical trials. Its possible place in the current antimicrobial outlook and in other infectious models is also discussed.

In Vitro Activity of Delafloxacin Tested against Isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis

Delafloxacin, an investigational anionic fluoroquinolone, is active against a broad range of Gram-positive and Gram-negative bacteria. In this study, 200 Streptococcus pneumoniae (plus 30 levofloxacin-resistant isolates), 200 Haemophilus influenzae, and 100 Moraxella catarrhalis isolates selected primarily from the United States (2014) were tested against delafloxacin and comparator agents. Delafloxacin was the most potent agent tested. MIC50 and MIC90 values against all S. pneumoniae isolates were 0.008 and 0.015 μg/ml. Delafloxacin susceptibility was not affected by β-lactamase status against H. influenzae and M. catarrhalis.

Delafloxacin, a non-zwitterionic fluoroquinolone in Phase III of clinical development: evaluation of its pharmacology, pharmacokinetics, pharmacodynamics and clinical efficacy

Delafloxacin is a fluoroquinolone lacking a basic substituent in position 7. It shows MICs remarkably low against Gram-positive organisms and anaerobes and similar to those of ciprofloxacin against Gram-negative bacteria. It remains active against most fluoroquinolone-resistant strains, except enterococci. Its potency is further increased in acidic environments (found in many infection sites). Delafloxacin is active on staphylococci growing intracellularly or in biofilms. It is currently evaluated as an intravenous and intravenous/oral stepdown therapy in Phase III trials for the treatment of complicated skin/skin structure infections. It was also granted as Qualified Infectious Disease Product for the treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia, due to its high activity on pneumococci and atypical pathogens.

Fluoroquinolones and Anaerobes

The usefulness of fluoroquinolones for the treatment of mixed aerobic and anaerobic infections has been investigated since these agents started being used in clinical practice. Newer compounds have increased in vitro activity against anaerobes, but clinically relevant susceptibility breakpoints for these bacteria have not been established. Pharmacodynamic analyses and corroboration by new data from clinical trials have enhanced our knowledge concerning the use of fluoroquinolones to treat selective anaerobic pathogens. These studies suggest that newer agents could be useful in the treatment of several types of mixed aerobic and anaerobic infections, including skin and soft-tissue, intra-abdominal, and respiratory infections. The major concerns with expanding the use of fluoroquinolones to treat anaerobic infections have been reports of increasing resistance in Bacteroides group isolates and the impact of these antibiotics on the incidence of Clostridium difficile-associated disease.

Comparative in vitro susceptibilities and bactericidal activities of investigational fluoroquinolone ABT-492 and other antimicrobial agents against human mycoplasmas and ureaplasmas

We determined in vitro susceptibilities for ABT-492 and other antimicrobials against Mycoplasma pneumoniae, Mycoplasma fermentans, Mycoplasma hominis, and Ureaplasma species. ABT-492 MICs were < or =1 microg/ml, and the agent was bactericidal against selected isolates of M. pneumoniae and M. hominis. ABT-492 has potential for treatment of infections due to these microorganisms.