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

In vitro activity of delafloxacin against clinical levofloxacin-resistant Helicobacter pylori isolates

BACKGROUND

Increasing antibiotic resistance in Helicobacter pylori necessitates research on new active molecules. In 2017, delafloxacin, a new fluoroquinolone with chemical properties of activity under acidic conditions, was approved for treatment of community-acquired bacterial pneumonia and acute bacterial skin and soft-tissue infections. Mutations in gyrA are responsible for fluoroquinolone resistance, but certain clinical isolates of H. pylori appear to display a dual phenotype: resistance to levofloxacin associated with very low delafloxacin MICs.

OBJECTIVES

To estimate epidemiological cut-off (ECOFF) values and to identify mutations in the gyrA gene, specific to FQ resistance, without increasing the MICs of delafloxacin.

METHODS

Clinical strains (n = 231) were collected in the bacteriology laboratory of Poitiers University Hospital over a 2 year period to determine the ECOFF of delafloxacin. Retrospectively, 101 clinical strains with an levofloxacin-resistant phenotype (MIC > 1 mg/L) were selected from 2018 to 2022 for delafloxacin MIC determination and QRDR (gyrA) sequencing.

RESULTS

The estimated ECOFF of delafloxacin was ≤0.125 mg/L. No H. pylori isolate showed a levofloxacin-sensitive phenotype with a delafloxacin MIC of >0.125 mg/L. Among the levofloxacin-resistant H. pylori isolates, 53.5% had delafloxacin MICs of ≤0.125 mg/L. The N87I mutation was associated with dual levofloxacin/delafloxacin resistance (P < 0.001) in contrast to the N87K and D91N mutations (P > 0.05). Mutations D91G and D91Y were not associated with a delafloxacin resistance phenotype (P > 0.05).

CONCLUSIONS

Delafloxacin seems to be a therapeutic alternative for levofloxacin-resistant strains with greater in vitro activity. However, further clinical/biological investigations are required to determine its efficacy in H. pylori eradication.

Role of parC Mutations at Position 84 on High-Level Delafloxacin Resistance in Methicillin-Resistant Staphylococcus aureus

High-level delafloxacin-resistant (H-L DLX-R) Staphylococcus aureus isolates (minimum inhibitory concentration ≥1 mg/L) associated with mutations affecting position 84 of ParC have emerged. We aimed to elucidate the role of these mutations as a mechanism of H-L DLX resistance in methicillin-resistant S. aureus (MRSA) isolates recovered from blood cultures. Susceptibility to DLX was determined in 75 MRSA isolates by E-test, and an rt-PCR was developed to detect mutations affecting position 84 of ParC to screen a further 185 MRSA isolates. The genomes of 48 isolates, including all DLX-R isolates or with alterations at position 84, and also a subset of DLX-susceptible isolates were analyzed. Among the 75 isolates studied, 77.34% were DLX-susceptible and only 4 H-L DLX-R isolates were found. Seven (3.8%) isolates with alterations at position 84 of ParC were detected by rt-PCR. Genomic analysis showed that 89.9% (8/9) of isolates with the substitution E84K/G in ParC, together with other mutations in gyrA and parC, were H-L DLX-R. However, the E84K substitution in ParC alone or with other alterations was found in two isolates without H-L DLX-R. Alterations at position 84 of ParC are rare but play a key role in H-L DLX resistance in MRSA but only when other alterations in GyrA are present.

Pharmacokinetics and pharmacodynamics of intravenous delafloxacin in healthy subjects: model-based dose optimization

Delafloxacin, a fluoroquinolone antibiotic to treat skin infections, exhibits a broad-spectrum antimicrobial activity. The first randomized, open-label phase I clinical trial was conducted to assess the safety and pharmacokinetics (PK) of intravenous delafloxacin in the Chinese population. A population pharmacokinetic (PopPK) model based on the clinical trial was conducted by NONMEM software. Monte Carlo simulation was performed to evaluate the antibacterial effects of delafloxacin at different doses in different Chinese populations. The PK characteristics of delafloxacin were best described by a three-compartment model with mixed linear and nonlinear clearance. Body weight was included as a covariate in the model. We simulated the AUC0-24h in a steady state at five doses in patient groups of various weights. The results indicated that for patients weighing 70 kg and treated with methicillin-resistant Staphylococcus aureus (MRSA) infections, a minimum dose of 300 mg achieved a PTA > 90% at MIC90 of 0.25 µg/mL, suggesting an ideal bactericidal effect. For patients weighing less than 60 kg, a dose of 200 mg achieved a PTA > 90% at MIC90 of 0.25 µg/mL, also suggesting an ideal bactericidal effect. Additionally, this trial demonstrated the high safety of delafloxacin in single-dose and multiple-dose groups of Chinese. Delafloxacin (300 mg, q12h, iv) was recommended for achieving optimal efficacy in Chinese bacterial skin infections patients. To ensure optimal efficacy, an individualized dose of 200 mg (q12h, iv) could be advised for patients weighing less than 60 kg, and 300 mg (q12h, iv) for those weighing more than 60 kg.

Comparison of the in vitro activities of delafloxacin and comparators against Staphylococcus epidermidis clinical strains involved in osteoarticular infections: a CRIOGO multicentre retrospective study

OBJECTIVES

Staphylococcus epidermidis bone and joint infections (BJIs) on material are often difficult to treat. The activity of delafloxacin has not yet been studied on S. epidermidis in this context. The aim of this study was to assess its in vitro activity compared with other fluoroquinolones, against a large collection of S. epidermidis clinical strains.

METHODS

We selected 538 S. epidermidis strains isolated between January 2015 and February 2023 from six French teaching hospitals. One hundred and fifty-two strains were ofloxacin susceptible and 386 were ofloxacin resistant. Identifications were performed by MS and MICs were determined using gradient concentration strips for ofloxacin, levofloxacin, moxifloxacin and delafloxacin.

RESULTS

Ofloxacin-susceptible strains were susceptible to all fluoroquinolones. Resistant strains had higher MICs of all fluoroquinolones. Strains resistant to ofloxacin (89.1%) still showed susceptibility to delafloxacin when using the Staphylococcus aureus 2021 CA-SFM/EUCAST threshold of 0.25 mg/L. In contrast, only 3.9% of the ofloxacin-resistant strains remained susceptible to delafloxacin with the 0.016 mg/L S. aureus breakpoint according to CA-SFM/EUCAST guidelines in 2022. The MIC50 was 0.094 mg/L and the MIC90 was 0.38 mg/L.

CONCLUSIONS

We showed low delafloxacin MICs for ofloxacin-susceptible S. epidermidis strains and a double population for ofloxacin-resistant strains. Despite the absence of breakpoints for S. epidermidis, delafloxacin may be an option for the treatment of complex BJI, including strains with MICs of ≤0.094 mg/L, leading to 64% susceptibility. This study underlines the importance for determining specific S. epidermidis delafloxacin breakpoints for the management of BJI on material.

New Antimicrobials for Gram-Positive Sustained Infections: A Comprehensive Guide for Clinicians

Antibiotic resistance is a public health problem with increasingly alarming data being reported. Gram-positive bacteria are among the protagonists of severe nosocomial and community infections. The objective of this review is to conduct an extensive examination of emerging treatments for Gram-positive infections including ceftobiprole, ceftaroline, dalbavancin, oritavancin, omadacycline, tedizolid, and delafloxacin. From a methodological standpoint, a comprehensive analysis on clinical trials, molecular structure, mechanism of action, microbiological targeting, clinical use, pharmacokinetic/pharmacodynamic features, and potential for therapeutic drug monitoring will be addressed. Each antibiotic paragraph is divided into specialized microbiological, clinical, and pharmacological sections, including detailed and appropriate tables. A better understanding of the latest promising advances in the field of therapeutic options could lead to the development of a better approach in managing antimicrobial therapy for multidrug-resistant Gram-positive pathogens, which increasingly needs to be better stratified and targeted.

Updated Review on Clinically-Relevant Properties of Delafloxacin

The extensive use of fluoroquinolones has been consequently accompanied by the emergence of bacterial resistance, which triggers the necessity to discover new compounds. Delafloxacin is a brand-new anionic non-zwitterionic fluoroquinolone with some structural particularities that give it attractive proprieties: high activity under acidic conditions, greater in vitro activity against Gram-positive bacteria-even those showing resistance to currently-used fluoroquinolones-and nearly equivalent affinity for both type-II topoisomerases (i.e., DNA gyrase and topoisomerase IV). During phases II and III clinical trials, delafloxacin showed non-inferiority compared to standard-of-care therapy in the treatment of acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia, which resulted in its approval in 2017 by the Food and Drug Administration for indications. Thanks to its overall good tolerance, its broad-spectrum in vitro activity, and its ease of use, it could represent a promising molecule for the treatment of bacterial infections.

Recent Advances in Pharmaceutical Approaches of Antimicrobial Agents for Selective Delivery in Various Administration Routes

Globally, the increase of pathogenic bacteria with antibiotic-resistant characteristics has become a critical challenge in medical treatment. The misuse of conventional antibiotics to treat an infectious disease often results in increased resistance and a scarcity of effective antimicrobials to be used in the future against the organisms. Here, we discuss the rise of antimicrobial resistance (AMR) and the need to combat it through the discovery of new synthetic or naturally occurring antibacterial compounds, as well as insights into the application of various drug delivery approaches delivered via various routes compared to conventional delivery systems. AMR-related infectious diseases are also discussed, as is the efficiency of various delivery systems. Future considerations in developing highly effective antimicrobial delivery devices to address antibiotic resistance are also presented here, especially on the smart delivery system of antibiotics.

The in vitro activity of delafloxacin and comparator agents against bacterial pathogens isolated from patients with cancer

Background

Fluoroquinolones are used for infection prevention in high-risk patients with haematological malignancies. Fluoroquinolones are active against many Gram-negative bacilli (GNB) but are less active against Gram-positive organisms. We evaluated the in vitro activity of delafloxacin and selected comparators against 560 bacterial pathogens isolated exclusively from patients with cancer.

Methods

Antimicrobial susceptibility testing and time-kill studies were performed using CLSI-approved methodology and interpretive criteria for 350 Gram-positive organisms and 210 GNB that had been recently isolated from patients with cancer.

Results

Delafloxacin was more active than ciprofloxacin and levofloxacin against Staphylococcus aureus and CoNS. Overall, 63% of staphylococcal isolates were susceptible to delafloxacin, 37% to ciprofloxacin and 39% to levofloxacin. Activity of delafloxacin against most Enterobacterales was similar to that of ciprofloxacin and levofloxacin. Escherichia coli and MDR Pseudomonas aeruginosa isolates had low susceptibility rates to the three tested fluoroquinolones. In time-kill studies delafloxacin and levofloxacin decreased the bacterial load to 3.0 log₁₀ in 8 and 13 h, respectively, using 8 × MIC.

Conclusions

Delafloxacin is more active than ciprofloxacin and levofloxacin against S. aureus but has substantial gaps in coverage against GNB. Resistance to all three fluoroquinolones could be high among leading GNB such as E. coli and P. aeruginosa, particularly in cancer centres where these agents are widely used as prophylactic agents.

Clinical Impact of Staphylococcus aureus Skin and Soft Tissue Infections

The pathogenic bacterium Staphylococcus aureus is the most common pathogen isolated in skin-and-soft-tissue infections (SSTIs) in the United States. Most S. aureus SSTIs are caused by the epidemic clone USA300 in the USA. These infections can be serious; in 2019, SSTIs with S. aureus were associated with an all-cause, age-standardized mortality rate of 0.5 globally. Clinical presentations of S. aureus SSTIs vary from superficial infections with local symptoms to monomicrobial necrotizing fasciitis, which can cause systemic manifestations and may lead to serious complications or death. In order to cause skin infections, S. aureus employs a host of virulence factors including cytolytic proteins, superantigenic factors, cell wall-anchored proteins, and molecules used for immune evasion. The immune response to S. aureus SSTIs involves initial responders such as keratinocytes and neutrophils, which are supported by dendritic cells and T-lymphocytes later during infection. Treatment for S. aureus SSTIs is usually oral therapy, with parenteral therapy reserved for severe presentations; it ranges from cephalosporins and penicillin agents such as oxacillin, which is generally used for methicillin-sensitive S. aureus (MSSA), to vancomycin for methicillin-resistant S. aureus (MRSA). Treatment challenges include adverse effects, risk for Clostridioides difficile infection, and potential for antibiotic resistance.

Efficacy of delafloxacin against the biothreat pathogen Bacillus anthracis

OBJECTIVES

To evaluate the in vitro activity and in vivo efficacy of delafloxacin against Bacillus anthracis, the causative agent of anthrax.

METHODS

MICs were obtained according to CLSI guidelines for 30 virulent isolates and 14 attenuated antibiotic-resistant strains. For the in vivo efficacy study, mice were administered delafloxacin (30-62.5 mg/kg) subcutaneously, or ciprofloxacin (30 mg/kg) intraperitoneally beginning at either 24 or 48 ± 1 h post-challenge (post-exposure prophylaxis) and continued every 12 h for 14 days with study termination on day 30. The mean inhaled dose in the study was approximately 103 × LD50 equivalents, and the range was 87-120 × LD50.

RESULTS

Delafloxacin (MIC90 = 0.004 mg/L) was 16-fold more potent than ciprofloxacin (MIC90 = 0.06 mg/L) against a 30-strain set of virulent B. anthracis. Against a panel of attenuated antibiotic-resistant strains, delafloxacin demonstrated potency ≥128-fold over that observed with ciprofloxacin. When evaluated in vivo, mice treated with all delafloxacin doses tested at 24 h post-challenge demonstrated equivalent survival compared with mice treated with the positive control ciprofloxacin. Because of the high challenge dose of spores, mice treated at 48 h showed rapid and high mortality in all groups including the positive control. Surviving animals in all delafloxacin- and ciprofloxacin-treated groups (24 and 48 h) showed complete splenic clearance of infection and <2.2 × 103 cfu/g lung tissue.

CONCLUSIONS

Given the high bar set by the 100 × LD50 challenge dose in this study, the results from delafloxacin treatment are promising for the treatment of inhaled anthrax.

Molecular Basis of Non-β-Lactam Antibiotics Resistance in Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most successful human pathogens with the potential to cause significant morbidity and mortality. MRSA has acquired resistance to almost all β-lactam antibiotics, including the new-generation cephalosporins, and is often also resistant to multiple other antibiotic classes. The expression of penicillin-binding protein 2a (PBP2a) is the primary basis for β-lactams resistance by MRSA, but it is coupled with other resistance mechanisms, conferring resistance to non-β-lactam antibiotics. The multiplicity of resistance mechanisms includes target modification, enzymatic drug inactivation, and decreased antibiotic uptake or efflux. This review highlights the molecular basis of resistance to non-β-lactam antibiotics recommended to treat MRSA infections such as macrolides, lincosamides, aminoglycosides, glycopeptides, oxazolidinones, lipopeptides, and others. A thorough understanding of the molecular and biochemical basis of antibiotic resistance in clinical isolates could help in developing promising therapies and molecular detection methods of antibiotic resistance.

The efficacy and adverse events of delafloxacin in the treatment of acute bacterial infections: A systematic review and meta-analysis of randomized controlled trials

Background: This study aims to assess the clinical efficacy and adverse events of delafloxacin for the treatment of acute bacterial infections in adult patients through meta-analysis.

Methods: The PubMed, Embase, Cochrane library, Web of Science, and Clinical trails databases were searched up to 26 March 2022. Only randomized controlled trials (RCTs) that evaluated delafloxacin and comparator antibiotics for treating acute bacterial infections in adult patients were included. The clinical cure rate and microbiological eradication rate at the posttreatment evaluation, while the secondary outcomes included the risk of adverse events (AEs).

Results: In total, six randomized controlled trials (RCTs) involving 3,019 patients with acute bacterial infection were included. There were no significant differences in the clinical cure rate between delafloxacin and comparators (OR = 1.06%, 95% CI = 0.89–1.26, I² = 0%). Overall, the results showed that delafloxacin had a microbiological eradication rate (documented and presumed) similar to the comparators (OR = 1.33%, 95% CI = 0.94–1.88, I² = 0%) in the pooled analysis of the six studies. Any treatment-emergent adverse events (TEAEs) did not show significant differences between delafloxacin and the comparators (OR = 0.93%, 95% CI = 0.80–1.08, I² = 75%). Serious adverse events (SAEs) did not differ between the delafloxacin and comparators (OR = 0.94%, 95% CI = 0.67–1.32, I² = 0%). The results of gastrointestinal disorders were (OR = 1.26%, 95% CI = 1.01–1.56, I² = 89%), and nausea, vomiting, and diarrhea were (OR = 0.77%, 95% CI = 0.45–1.34, I² = 79%), (OR = 1.00%, 95% CI = 0.74–1.36, I² = 72%), and (OR = 2.10%, 95% CI = 1.70–2.96, I² = 0%), respectively. The results showed that there was no significant difference in the incidence of nausea and vomiting between delafloxacin and the comparator, but the incidence of diarrhea was higher. The analysis of neurological disorders indicated that the incidence of nervous system disorders was lower in the delafloxacin group (OR = 0.71%, 95% CI = 0.50–1.01, I² = 52%).

Conclusion: The clinical efficacy, microbiological eradication rate and the incidence of AEs of delafloxacin in the treatment of acute bacterial infections were similar to those of the comparators, as an alternative therapeutic agent.

Current and future options for treating complicated skin and soft tissue infections: focus on fluoroquinolones and long-acting lipoglycopeptide antibiotics

Bacterial skin and soft tissue infections are among the most common bacterial infections and constitute a major burden for patients and healthcare systems. Care is complicated by the variety of potential pathogens, some with resistance to previously effective antimicrobial agents, the wide spectrum of clinical presentations and the risk of progression to life-threatening forms. More-efficient care pathways are needed that can reduce hospital admissions and length of stay, while maintaining a high quality of care and adhering to antimicrobial stewardship principles. Several agents approved recently for treating acute bacterial skin and skin structure infections have characteristics that meet these requirements. We address the clinical and pharmacological characteristics of the fourth-generation fluoroquinolone delafloxacin, and the long-acting lipoglycopeptide agents dalbavancin and oritavancin.

Comparative efficacy of delafloxacin for complicated and acute bacterial skin and skin structure infections: results from a network meta-analysis

BACKGROUND

Delafloxacin is a novel fluoroquinolone with broad antibacterial activity against pathogens causing acute bacterial skin and skin structure infections (ABSSSI). This network meta-analysis (NMA) was conducted to evaluate the relative efficacy of delafloxacin versus other comparators used for managing patients with ABSSSI.

METHODS

A systematic literature review was conducted to identify randomised controlled trials (RCTs) evaluating adults (≥ 18 years) with ABSSSI, complicated SSSI (cSSSI), complicated skin and soft tissue infections (cSSTI) or severe cellulitis with pathogen of gram-positive, gram-negative, or mixed aetiology. OVID MEDLINE^®, Embase, Epub Ahead of Print, Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews were searched from inception through 12 April 2019. A feasibility assessment was conducted, followed by an NMA, which was run in a Bayesian framework. The interventions included in the NMA encompassed monotherapy or combination therapies of amoxicillin/clavulanate, ampicillin/sulbactam, ceftaroline, ceftobiprole, dalbavancin, daptomycin, delafloxacin, fusidic acid, iclaprim, linezolid, omadacycline, oxacillin + dicloxacillin, standard therapy, tedizolid, telavancin, tigecycline, vancomycin, vancomycin + aztreonam and vancomycin + linezolid.

RESULTS

A feasibility assessment was performed and evidence networks were established for composite clinical response (n = 34 studies), early clinical response (n = 16 studies) and microbiological response (n = 14 studies) in the overall study population, composite clinical response (n = 4 studies) in obese subpopulation and for composite clinical response (n = 18 studies) and microbiological response (n = 14 studies) in patients with methicillin-resistant Staphylococcus aureus (MRSA) infection. Delafloxacin performed significantly better than fusidic acid, iclaprim, vancomycin, and ceftobiprole for composite clinical response. Delafloxacin was comparable to dalbavancin, daptomycin, fusidic acid, iclaprim, linezolid, omadacycline, tedizolid, vancomycin, vancomycin + aztreonam and vancomycin + linezolid in the analysis of early clinical response, whereas for microbiological response, delafloxacin was comparable to all interventions. In the obese subpopulation, the results favoured delafloxacin in comparison to vancomycin, whilst the results were comparable with other interventions among the MRSA subpopulation.

CONCLUSIONS

Delafloxacin is a promising new antibiotic for ABSSSI demonstrating greater improvement (composite clinical response) compared to ceftobiprole, fusidic acid, iclaprim, telavancin and vancomycin and comparable effectiveness versus standard of care for all outcomes considered in the study.

Efficacy of Delafloxacin against the Biothreat Pathogen Burkholderia pseudomallei

The in vitro activity and in vivo efficacy of delafloxacin were evaluated against the causative pathogen of melioidosis, Burkholderia pseudomallei. Delafloxacin MICs were determined by broth microdilution according to CLSI guidelines for 30 isolates of B. pseudomallei. The in vivo efficacy of delafloxacin was studied at a range of doses in a postexposure prophylaxis (PEP) murine model of melioidosis. Delafloxacin was active in vitro against B. pseudomallei (MIC90, 1 μg/ml). When the mice were dosed with 50 mg/kg body weight and 80 mg/kg body weight delafloxacin at both 16 and 24 h, greater survival was observed (90% to 100% survival) than with the 30-mg/kg-dosed mice (70% survival). All delafloxacin-treated cohorts contained no detectable B. pseudomallei in the spleens at the end of the study. This contrasts with ceftazidime 16- and 24-h administration, which had 40% and 20% survival, respectively. Complete clearance of infection was observed for most but not all surviving cohorts administered ceftazidime. In the mouse model of infection, survival curves for delafloxacin- and ceftazidime-treated animals at treatment start times of 16 and 24 h were statistically significant (P values of <0.0001). Estimated daily delafloxacin exposures in the B. pseudomallei murine aerosol study were similar to daily human exposures with the approved twice a day (BID) intravenous (i.v.) (300 mg) or oral (450 mg) dosing regimens. Based on its in vitro and in vivo activity, its safety, and its tolerability profile, delafloxacin may offer an attractive treatment option as PEP or eradication therapy for B. pseudomallei. Evaluation in other in vivo infection models for B. pseudomallei should be considered.

Potential role of new-generation antibiotics in acute bacterial skin and skin structure infections

PURPOSE OF REVIEW

To summarize the available results of primary analyses from high-quality randomized studies of either recently approved or possible future agents for the treatment of acute bacterial skin and skin structure infections (ABSSSI).

RECENT FINDINGS

In the last 2 decades, several novel agents have been approved for the treatment of ABSSSI, that are also active against methicillin-resistant Staphylococcus aureus (MRSA). In addition to already available agents, further molecules are in clinical development that could become available for treating ABSSSI in the forthcoming future.

SUMMARY

The current and future availability of several new-generation antibiotics will allow to modulate therapeutic choices not only on efficacy but also on other relevant factors such as the combination of the drug safety profile and the comorbidities of any given patient, the expected adherence to outpatient therapy, and the possibilities of early discharge or avoiding hospitalization by means of oral formulations, early switch from intravenous to oral therapy, or single-dose administration of long-acting intravenous agents. With the advent of new-generation antibiotics, all these factors are becoming increasingly essential for tailoring treatment to individual patients in line with the principles of personalized medicine, and for optimizing the use of healthcare resources.

Delafloxacin: A Review in Acute Bacterial Skin and Skin Structure Infections

The global spread of antibacterial-resistant strains, especially methicillin-resistant Staphylococcus aureus (MRSA) for acute bacterial skin and skin structure infections (ABSSSIs), has driven the need for novel antibacterials. Delafloxacin [Quofenix™ (EU); Baxdela^® (USA)], a new fluoroquinolone (FQ), has a unique chemical structure that enhances its antibacterial activity in acidic environments such as occurs in ABSSSIs (including S. aureus infections). Delafloxacin (intravenous and oral formulations) is approved in several countries for the treatment of adults with ABSSSIs (featured indication). In intent-to-treat analyses in pivotal phase 3 trials in adults with ABSSSIs, including those with comorbid disease, intravenous delafloxacin monotherapy (± oral switch after six doses) twice daily was noninferior to intravenous vancomycin + aztreonam for primary endpoints, as specified by the FDA (objective response rate at 48–78 h after initiation of therapy) and the EMA [investigator-assessed clinical cure rate at the follow-up visit at day 14 (± 1 day)]. Delafloxacin was generally well tolerated, with most treatment-related adverse events mild to moderate in severity and few patients discontinuing treatment because of these events. Relative to vancomycin + aztreonam (a non-FQ regimen), delafloxacin treatment was not associated with an increased risk of FQ-associated AEs of special interest. Given its unique chemical structure that confers novel properties relative to other FQ and its broad spectrum of activity against common clinically relevant Gram-positive pathogens, including against MRSA strains (± FQ-resistance mutations), and Gram-negative pathogens, intravenous delafloxacin (± oral switch) provides a novel emerging option for the treatment of adult patients with ABSSSIs.

[In vitro activity of delafloxacin against bacterial isolates from osteoarticular and skin infections in Buenos Aires, Argentina]

In vitro activities of delafloxacin, ciprofloxacin and levofloxacin were evaluated by epsilometric and disk diffusion methods against 181 bacterial isolates recovered from bone and skin infections. Isolates included were 84 Staphylococcus aureus (40 MRSA and 44 MSSA), 46 coagulase-negative staphylococci (CNS), 23 Klebsiella pneumoniae and 28 Pseudomonas aeruginosa. The MIC₅₀/MIC₉₀ (mg/l) for delafloxacin, ciprofloxacin and levofloxacin, respectively, were: MRSA, 0.004/0.064, 0.25/16 and 0.125/4; MSSA, 0.002/0.004, 0.125/0.25 and 0.125/0.25; CNS, 0.008/0.25, 0.125/>32 and 0.25/>32; K. pneumoniae, 4/>32,>32/>32 and 16/>32; P. aeruginosa, 1/>32, 0,5/>32 and 4/>32. Susceptibilities for delafloxacin, ciprofloxacin and levofloxacin, respectively, were: MRSA, 97.5%, 82.5% and 82.5%; MSSA, 97.7%, 95.5% and 95.5%; CNS, 93.5%, 63.0% and 60.9%; K. pneumoniae, 21.7%, 26.1% and 43.5%; P aeruginosa, 35.7%, 53.6% and 42.8%. The disk diffusion and epsilometric methods were concordant for evaluating in vitro susceptibility in staphylococci (categorical concordance of 98.8% for S. aureus and 91.3% for CNS).

Serotype distribution and antimicrobial susceptibility of Streptococcus pneumoniae isolates from a Phase III community-acquired bacterial pneumonia (CABP) trial

Objectives

To report Streptococcus pneumoniae serotyping and susceptibility data from a recent clinical trial (ML-3341-306) comparing delafloxacin with moxifloxacin in the treatment of adults with community-acquired bacterial pneumonia (CABP).

Methods

Serotyping and susceptibility testing were conducted on 142 baseline S. pneumoniae isolates recovered from subjects participating in a CABP clinical trial.

Results

Overall, 113/142 (79.6%) isolates were vaccine serotypes. 76.8% (109/142) of serotyped isolates were PPSV23 serotypes and 59.9% (85/142) of isolates were PCV13 serotypes. 15.5% (22/142) of serotyped isolates were serotypes not covered by either vaccine; 4.9% (7/142) of tested isolates were non-typeable. The most common serotypes were serotypes 3 (19.0%; 27/142), 19F (9.9%; 14/142) and 23F (7.0%; 10/142). All of the 142 isolates were susceptible to delafloxacin and moxifloxacin, 76.1% were susceptible to azithromycin and 71.8% were susceptible to penicillin. Multidrug resistance was found among 19A (4/5; 80%), 6A (1/4; 25%), 6B (1/4; 25%), 14 (1/4; 25%), 19F (1/14; 7.1%), and 23F serotypes (2/10; 20%), and among non-typeable S. pneumoniae isolates (1/7; 14.3%).

Conclusions

S. pneumoniae vaccine-targeted serotypes were the main cause of CABP in this Phase 3 CABP study. Fluoroquinolones including delafloxacin remain a good treatment option for CABP in adults caused by S. pneumoniae.

New-Generation Antibiotics for Treatment of Gram-Positive Infections: A Review with Focus on Endocarditis and Osteomyelitis

Infective endocarditis, osteomyelitis, and osteosynthesis-associated infections are mostly caused by Gram-positive bacteria. They are often difficult to treat and are associated with a poor prognosis. In the past 20 years, nine antibiotic drugs with predominant activity against Gram-positive bacteria have been introduced and approved by the Food and Drug Administration or the European Medicines Agency: ceftaroline, daptomycin, telavancin, dalbavancin, oritavancin, linezolid, tedizolid, delafloxacin, and omadacycline. This narrative review aims to provide an overview on these antibiotics with a special focus on their use in infective endocarditis, osteomyelitis, and osteosynthesis-associated infections. Although some of these approved antibiotics are promising, they should not be used as first- or second-line therapy, awaiting more clinical data.

Present and Future Perspectives on Therapeutic Options for Carbapenemase-Producing Enterobacterales Infections

Carbapenem-resistant Enterobacterales (CRE) are included in the list of the most threatening antibiotic resistance microorganisms, being responsible for often insurmountable therapeutic issues, especially in hospitalized patients and immunocompromised individuals and patients in intensive care units. The enzymatic resistance to carbapenems is encoded by different β-lactamases belonging to A, B or D Ambler class. Besides compromising the activity of last-resort antibiotics, CRE have spread from the clinical to the environmental sectors, in all geographic regions. The purpose of this review is to present present and future perspectives on CRE-associated infections treatment.

Cellulitis

Cellulitis is a common infection of the skin and subcutaneous tissue caused predominantly by gram-positive organisms. Risk factors include prior episodes of cellulitis, cutaneous lesions, tinea pedis, and chronic edema. Cellulitis is a clinical diagnosis and presents with localized skin erythema, edema, warmth, and tenderness. Uncomplicated cellulitis can be managed in the outpatient setting with oral antibiotics. Imaging often is not required but can be helpful. Recurrent cellulitis is common and predisposing conditions should be assessed for and treated at the time of initial diagnosis. For patients with frequent recurrences despite management of underlying conditions, antimicrobial prophylaxis can be effective.

Emergence of Delafloxacin-Resistant Staphylococcus aureus in Brooklyn, New York

Delafloxacin is an option for infections due to methicillin-resistant Staphylococcus aureus. In 2017, 22% of isolates from 7 hospitals in Brooklyn, New York, were nonsusceptible to delafloxacin. Isolates belonging to ST105, a strain associated with healthcare-related infections, predominated. Resistance was also found in ST8, a strain (USA300) associated with community-associated infections.

New Antibiotics for the Treatment of Acute Bacterial Skin and Soft Tissue Infections in Pediatrics

Acute bacterial skin and soft tissue infections (aSSTIs) are a large group of diseases that can involve exclusively the skin or also the underlying subcutaneous tissues, fascia, or muscles. Despite differences in the localization and severity, all these diseases are due mainly to Gram-positive bacteria, especially Staphylococcus aureus and Streptococcus pyogenes. aSSTI incidence increased considerably in the early years of this century due to the emergence and diffusion of community-acquired methicillin-resistant S. aureus (CA-MRSA). Despite the availability of antibiotics effective against CA-MRSA, problems of resistance to these drugs and risks of significant adverse events have emerged. In this paper, the present knowledge on the potential role new antibiotics for the treatment of pediatric aSSTIs is discussed. The most recent molecules that have been licensed for the treatment of aSSTIs include ozenoxacin (OZ), ceftaroline fosamil (CF), dalbavancin (DA), oritavancin (OR), tedizolid (TD), delafloxacin (DL), and omadacycline (OM). However, only OZ and CF have been licensed for use in children with aSSTIs, although the superiority of these antibiotics to those routinely used for the treatment of aSSTIs should be further demonstrated. Waiting for additional studies, OZ and CF should be prescribed for aSSTI treatment in the presence of the potential failure of old molecules.

Update on the activity of delafloxacin against acute bacterial skin and skin-structure infection isolates from European hospitals (2014-2019)

OBJECTIVES

Delafloxacin is a broad-spectrum anionic fluoroquinolone with activity against Gram-positive and Gram-negative organisms, including methicillin-resistant Staphylococcus aureus. Both oral and intravenous formulations were approved for use in the treatment of acute bacterial skin and skin-structure infections (ABSSSIs) due to Gram-positive and Gram-negative organisms by the US Food and Drug Administration (2017) and European Medicines Agency (2019), and for community-acquired bacterial pneumonia by the FDA (2019). The SENTRY Antimicrobial Surveillance Program has monitored the susceptibility of delafloxacin in the USA and Europe since 2014. The purpose of this study is to provide an update on delafloxacin activity against ABSSSI isolates primarily collected from hospitalised patients in Europe.

METHODS

A total of 11,866 non-duplicate ABSSSI isolates were collected from 2014 to 2019 from 46 European medical centres in 24 countries. Susceptibilities were determined by broth microdilution. Results were interpreted using European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints (2020).

RESULTS

The most common isolate wasS. aureus (37.8%; n = 4484), followed by Escherichia coli (11.0%) and Streptococcus spp. (10.0%). Delafloxacin susceptibility for S. aureus was 92.4% (MIC_50/90, ≤0.004/0.25 mg/L), streptococci 98.4% and E. coli 58.1%. Delafloxacin was more active against S. aureus than levofloxacin (84.0% intermediate; MIC_50/90, 0.25/>4 mg/L) and moxifloxacin (84.3% susceptible; MIC_50/90, ≤0.06/2 mg/L). Susceptibility of E. coli was similar for the three quinolones.

CONCLUSIONS

Delafloxacin had broad-spectrum activity and improved potency against Gram-positive pathogens compared with levofloxacin and moxifloxacin. These data suggest that delafloxacin may be a useful therapeutic choice for the most common causes of ABSSSI.

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.

Drugs for Gram-Negative Bugs From 2010-2019: A Decade in Review

A literature review spanning January 1, 2010, to December 31, 2019, was conducted using the PubMed and ISI Web of Science databases to determine the breadth of publication activity in the area of gram-negative bacteria antimicrobial therapy. The number of articles was used as a reflection of scholarly activity. First, PubMed was searched using the following Medical Subject Headings (MeSH): antibacterial agents, Enterobacteriaceae, Acinetobacter, and Pseudomonas. A total of 12 643 articles were identified within PubMed, and 77 862 articles were identified within ISI Web of Science that included these terms. Second, these articles were categorized by antibiotic class to identify relative contributions to the literature by drug category. Third, these studies were used to identify key trends in the treatment of gram-negative bacterial infections from the past decade. This review highlights advances made in the past 10 years in antibacterial pharmacotherapy and some of the challenges that await the next decade of practice.

Current Treatment Options for Acute Skin and Skin-structure Infections

Acute bacterial skin and skin-structure infections (ABSSSIs) are a common reason for seeking care at acute healthcare facilities, including emergency departments. Staphylococcus aureus is the most common organism associated with these infections, and the emergence of community-associated methicillin-resistant Staphylococcus aureus (MRSA) has represented a considerable challenge in their treatment. To address this need, a number of new antibiotics have been developed for the treatment of ABSSSIs in the past several years. Most of these agents focus primarily on gram-positive organisms, particularly MRSA; however, there has not been an oral agent that can reliably treat MRSA, as well as relevant gram-negative pathogens. Acute skin infections that involve mixed gram-positive and gram-negative pathogens must also be considered as they can be associated with discordant antimicrobial therapy. Here, I review ABSSSI treatment guidelines in the hospital setting and discuss current and future antibiotic options for treatment of this commonly encountered infection.

In vitro Susceptibilities of Methicillin-Susceptible and Resistant Staphylococci to Traditional Antibiotics Compared to a Novel Fluoroquinolone

Background

To assess the in-vitro efficacy of delafloxacin, a new fourth generation fluoroquinolone, against Staphylococcus vitreous isolates from patients with clinically diagnosed endophthalmitis. This is the first investigation of delafloxacin in ocular tissues.

Methods

Intravitreal isolates of culture-proven S. aureus and S. epidermidis were identified between 2014 and 2018. Minimum inhibitor concentrations (MIC) were determined using ETEST strips. The antibiotic susceptibilities were tested against a panel of drugs including glycopeptides such as vancomycin, as well as traditional and newer fluoroquinolones (levofloxacin, moxifloxacin, and delafloxacin).

Results

Of 45 total isolates identified between 2014 and 2018, 13% (6) were methicillin-resistant S. aureus (MRSA), 9% (4) were methicillin-sensitive S. aureus (MSSA), 53% (24) were methicillin-resistant S. epidermidis (MRSE), and 24% (11) were methicillin-sensitive S. epidermidis (MSSE). Among the fluoroquinolones, resistance rates were 61% for levofloxacin, 50% for moxifloxacin, and 12% for delafloxacin. Inter-class comparisons between delafloxacin and the two other fluoroquinolones demonstrated higher Gram-positive susceptibility to delafloxacin (p < 0.01). MIC90 values were lowest for delafloxacin (1.0 μg/mL) compared to levofloxacin (8.0 μg/mL) and moxifloxacin (8.0 μg/mL). Vancomycin was 100% effective against all isolates with MIC90 value of 0.75 μg/mL.

Conclusion

Compared to levofloxacin and moxifloxacin, the newer fluoroquinolone delafloxacin demonstrated the lowest MICs values and lowest rates of resistance for Gram-positive in-vitro S. epidermidis and S. aureus vitreous isolates.

Efficacy of Delafloxacin versus Moxifloxacin against Bacterial Respiratory Pathogens in Adults with Community-Acquired Bacterial Pneumonia (CABP): Microbiology Results from the Delafloxacin Phase 3 CABP Trial

Delafloxacin is a novel fluoroquinolone with activity against Gram-positive, Gram-negative, and atypical pathogens, including fluoroquinolone-nonsusceptible methicillin-resistant Staphylococcus aureus (MRSA). The microbiological results of a phase 3 clinical trial in adults with community-acquired pneumonia (CAP) comparing delafloxacin (300 mg intravenously [i.v.] with the option to switch to 450 mg orally every 12 h) to moxifloxacin (400 mg i.v.

Delafloxacin is a novel fluoroquinolone with activity against Gram-positive, Gram-negative, and atypical pathogens, including fluoroquinolone-nonsusceptible methicillin-resistant Staphylococcus aureus (MRSA). The microbiological results of a phase 3 clinical trial in adults with community-acquired pneumonia (CAP) comparing delafloxacin (300 mg intravenously [i.v.] with the option to switch to 450 mg orally every 12 h) to moxifloxacin (400 mg i.v. with the option to switch to 400 mg orally once a day [QD]) were determined. Patients from 4 continents, predominately Europe but also South America and Asia, were enrolled. The microbiological intent-to-treat (MITT) population included 520 patients, and 60.5% of these patients had a bacterial pathogen identified. Multiple diagnostic methods were employed, including culture, serology, PCR, and urinary antigen tests. Based on baseline MIC₉₀ values, delafloxacin exhibited at least 16-fold greater activity than moxifloxacin for Gram-positive and fastidious Gram-negative pathogens. Delafloxacin retained activity against resistant phenotypes found in Streptococcus pneumoniae (penicillin-, macrolide-, and multiple-drug resistant), Haemophilus species (β-lactamase producing and macrolide nonsusceptible), and S. aureus (MRSA and fluoroquinolone-nonsusceptible methicillin-susceptible S. aureus [MSSA]). The microbiological success rates were 92.7% for S. pneumoniae (87.5% for penicillin-resistant S. pneumoniae [PRSP]), 92.6% for S. aureus (100% for MRSA), 100% for Escherichia coli, 82.4% for Klebsiella pneumoniae, 100% for Klebsiella oxytoca, 100% for Moraxella catarrhalis, 91.7% for Haemophilus influenzae, 88.6% for Haemophilus parainfluenzae, 96.7% for Mycoplasma pneumoniae, 93.1% for Legionella pneumophila, and 100% for Chlamydia pneumoniae. There was little correlation between MICs and outcomes, with a high proportion of favorable outcomes observed across all delafloxacin baseline MIC values. Delafloxacin may be considered a treatment option as monotherapy for CAP in adults, where broad-spectrum coverage including MRSA activity is desirable.

A Phase 3 Study to Compare Delafloxacin With Moxifloxacin for the Treatment of Adults With Community-Acquired Bacterial Pneumonia (DEFINE-CABP)

BACKGROUND

The clinical and economic burden of community-acquired bacterial pneumonia (CABP) is significant and is anticipated to increase as the population ages and pathogens become more resistant. Delafloxacin is a fluoroquinolone antibiotic approved in the United States for the treatment of adults with acute bacterial skin and skin structure infections. Delafloxacin's shape and charge profile uniquely impact its spectrum of activity and side effect profile. This phase 3 study compared the efficacy and safety of delafloxacin with moxifloxacin for the treatment of CABP.

METHODS

A randomized, double-blind, comparator-controlled, multicenter, global phase 3 study compared the efficacy and safety of delafloxacin 300 mg twice daily or moxifloxacin 400 mg once daily in adults with CABP. The primary end point was early clinical response (ECR), defined as improvement at 96 (±24) hours after the first dose of study drug. Clinical response at test of cure (TOC) and microbiologic response were also assessed.

RESULTS

In the intent-to-treat analysis population (ITT), ECR rates were 88.9% in the delafloxacin group and 89.0% in the moxifloxacin group. Noninferiority of delafloxacin compared with moxifloxacin was demonstrated. At TOC in the ITT population, the success rates were similar between groups. Treatment-emergent adverse events that were considered at least possibly related to the study drug occurred in 65 subjects (15.2%) in the delafloxacin group and 54 (12.6%) in the moxifloxacin group.

CONCLUSIONS

Intravenous/oral delafloxacin monotherapy is effective and well tolerated in the treatment of adults with CABP, providing coverage for Gram-positive, Gram-negative, and atypical pathogens.

CLINICALTRIALSGOV IDENTIFIER

NCT03534622.

FDA approved antibacterial drugs: 2018-2019

Bacterial resistance to existent antibiotherapy is a perpetual internationally-recognized problem. Year after year, there is a continuous need for novel antibacterial drugs and this research and development efforts recently resulted in few new drugs or combination of drugs proposed for the use into the clinic. This review focuses on the novel US FDA approved antibacterial agents in the last two years (2018-2019). Plazomicin, eravacycline, sarecycline, omadacycline, rifamycin (2018) and imipenem, cilastatin and relebactam combination, pretomanid, lefamulin, cefiderocol (2019) are new therapeutic options. Plazomicin aminoglycoside antibiotic targets Enterobacteriaceae infections, being mainly used for the complicated urinary tract infections. The fully synthetic fluorocycline eravacycline gained approval for the complicated intra-abdominal infections. The tetracycline-derived antibiotic sarecycline might be a useful strategy for the management of non-nodular moderate to severe acne, while the other tetracycline-derived antibiotic approved, omadacycline, may be used for the patients with acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia. The already-known RNA-synthesis suppressor rifamycin is now also approved for noninvasive Escherichia Coli-caused travelers' diarrhea. Two combinatorial strategies were approved for complicated urinary tract infections, complicated intra-abdominal infections (imipenem, cilastatin and relebactam) and lung tuberculosis (pretomanid in combination with bedaquiline and linezolid). Lefamulin is a semisynthetic pleuromutilin antibiotic for community-acquired bacterial pneumonia, while cefiderocol, a cephalosporin antibiotic is the last antibacterial drug approved in 2019, for the use in complicated urinary tract infections. Despite of these new developments, there is an ongoing need and urgency to develop novel antibiotic strategies and drugs to overrun the bacterial resistance to antibiotics.

Clinical Pharmacokinetics and Pharmacodynamics of Delafloxacin

Delafloxacin has recently received approval by the US Food and Drug Administration for the treatment of acute bacterial skin and skin structure infections. This article provides a balanced and comprehensive systematic critique of the literature in order to provide an up-to-date summary of its clinical pharmacology. Oral delafloxacin is rapidly absorbed and exhibits comparable exposure characteristics (300 mg intravenous versus 450 mg oral) between the two formulations, allowing easy transition from intravenous to oral therapy. The bioavailability is high (60-70%) and absorption is not affected by food intake, although further studies are required under clinically relevant conditions. Delafloxacin is primarily excreted renally (thus requiring renal dose adjustment in the setting of renal dysfunction), but also undergoes metabolism by uridine diphosphate-glucuronosyltransferase enzymes in the formation of a conjugated metabolite. Few drug-drug interaction studies have been identified, although more systematic characterizations in vitro and in vivo are warranted. Delafloxacin is a concentration-dependent bactericidal agent that has in vitro susceptibility for gram-positive (notably potent activity against methicillin-resistant Staphylococcus aureus), gram-negative, and anaerobic organisms. In addition to acute bacterial skin and skin structure infections, the clinical utility of delafloxacin has also been studied in community-acquired pneumonia, acute exacerbation of chronic bronchitis, and gonorrhea, with potentially promising findings. Given its mild side effect profile, including an apparent lack of association with clinically important QTc prolongation, delafloxacin is generally well tolerated.

A Comparison of the Efficacy and Safety of Intravenous Followed by Oral Delafloxacin With Vancomycin Plus Aztreonam for the Treatment of Acute Bacterial Skin and Skin Structure Infections: A Phase 3, Multinational, Double-Blind, Randomized Study

Background

Delafloxacin is an intravenous (IV)/oral anionic fluoroquinolone with activity against gram-positive (including methicillin-resistant Staphylococcus aureus [MRSA]), gram-negative, atypical, and anaerobic organisms. It is approved in the United States for acute bacterial skin and skin structure infections (ABSSSIs) caused by designated susceptible gram-positive and gram-negative organisms, and is in development for the treatment of community-acquired bacterial pneumonia.

Methods

A multicenter, randomized, double-blind trial of 850 adults with ABSSSI compared delafloxacin 300 mg IV every 12 hours for 3 days with a switch to 450 mg oral delafloxacin, to vancomycin 15 mg/kg IV with aztreonam for 5–14 days. The primary endpoint was objective response at 48–72 hours. Investigator-assessed response based on resolution of signs and symptoms at follow-up (day 14 ± 1), and late follow-up (day 21–28) were secondary endpoints.

Results

In the intent-to-treat analysis set, the objective response was 83.7% in the delafloxacin arm and 80.6% in the comparator arm. Investigator-assessed success was similar at follow-up (87.2% vs 84.4%) and late follow-up (83.5% vs 82.2%). Delafloxacin was comparable to vancomycin + aztreonam in eradication of MRSA at 96.0% vs 97.0% at follow-up. Frequency of treatment-emergent adverse events between the groups was similar. Treatment-emergent adverse events leading to study drug discontinuation was higher in the vancomycin + aztreonam group (1.2% vs 2.4%).

Conclusions

In ABSSSI patients, IV/oral delafloxacin monotherapy was noninferior to IV vancomycin + aztreonam combination therapy for both the objective response and the investigator-assessed response at follow-up and late follow-up. Delafloxacin was well tolerated as monotherapy in treatment of ABSSSIs.

Clinical Trials Registration

NCT01984684.

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.

In Vivo Pharmacodynamic Target Determination for Delafloxacin against Klebsiella pneumoniae and Pseudomonas aeruginosa in the Neutropenic Murine Pneumonia Model

Delafloxacin is a broad-spectrum anionic fluoroquinolone that has completed a phase 3 study for community-acquired bacterial pneumonia. We investigated the pharmacodynamic target for delafloxacin against 12 Klebsiella pneumoniae and 5 Pseudomonas aeruginosa strains in the neutropenic murine lung infection model. The median 24-h free-drug area under the curve (fAUC)/MIC values associated with net stasis and 1-log kill were 28.6 and 64.1 for K. pneumoniae, respectively. The 24-h fAUC/MIC values associated with net stasis and 1-log kill for P. aeruginosa were 5.66 and 14.3, respectively.

Antibacterials in the pipeline and perspectives for the near future

Antimicrobial resistance is a global threat to the management of infections in our patients. Sound stewardship of antibacterial agents at our disposal must be accompanied by a concerted effort to develop new agents to bolster our armamentarium. This review will cover the latest antibiotics that have come through the pipeline and the role they can play in the management of infections that are increasingly difficult to treat due to resistance mechanisms.

Developments on antibiotics for multidrug resistant bacterial Gram-negative infections

Introduction: The constantly increasing spread of severe infections due to multidrug-resistant (MDR) Gram-negative bacteria (GNB) is a critical threat to the global medical community. After a long period of antibiotic pipeline pause, new antibiotic compounds are commercially available or are at late stages of clinical evaluation, promising to augment the therapeutic armamentarium of clinicians against deadly pathogens. Areas covered: This review summarizes available data regarding agents with potent activity against critical MDR Gram-negative pathogens, which urgently require new efficient antibiotics. Recently approved antibiotic formulations; and agents in advanced stages of development, including combinations of β-lactam/β-lactamase inhibitor, novel cephalosporins (cefiderocol), tetracyclines (eravacycline), aminoglycosides (plazomicin), quinolones (delafloxacin and finafloxacin) and pleuromutilins (lefamulin) are discussed in this review. Expert opinion: The recent introduction of new antibiotics into clinical practice is an encouraging step after a long period of pipeline stagnation. New formulations will be a useful option for clinicians to treat serious infections caused by several MDR Gram-negative pathogens. However, most of the new compounds are based on modifications of traditional antibiotic structures challenging their longevity as therapeutic options. More investment is needed for the discovery and clinical development of truly innovative and effective antibiotics without cross-resistance to currently used antibiotics.

Efficacy and safety of delafloxacin in the treatment of acute bacterial skin and skin structure infections: a systematic review and meta-analysis of randomized controlled trials

Purpose: To assess the clinical efficacy and safety of delafloxacin for treating acute bacterial skin and skin structure infections (ABSSSIs) in adult patients.

Patients and methods: The Cochrane Library, EBSCO, EMBASE, Ovid Medline, PubMed, and Web of Science databases were searched up to November 2018. Only randomized controlled trials (RCTs) that evaluated delafloxacin and other comparators for the treatment of ABSSSIs were included. The primary outcome was the clinical cure rate and the secondary outcomes were microbiological response and the risk of adverse events.

Results: Four RCTs were included. Overall, delafloxacin exhibited a clinical cure rate similar to the rates of the comparator drugs in the treatment of ABSSSI (OR, 1.05; 95% CI, 0.87–1.27, I²=16%) and methicillin-resistant Staphylococcus aureus (MRSA)-associated ABSSSI (OR, 1.12; 95% CI, 0.71–1.77, I²=0%). Delafloxacin had a microbiological eradication (documented and presumed) rate similar to the rates of the comparators in the treatment of ABSSSI (OR, 1.21; 95% CI, 0.58–2.50, I²=0%) and MRSA-associated ABSSSIs (OR, 1.16; 95% CI, 0.37–3.60, I²=0%). Delafloxacin and the comparators did not differ significantly in the risk of serious adverse events (AEs), treatment-emergent adverse events (TEAEs), and TEAEs related to the study drug. However, the risk of discontinuation of the study drug due to an AE was lower for delafloxacin than for the comparators (OR, 0.33; 95% CI, 0.15–0.74, I²=0%).

Conclusion: The clinical efficacy of delafloxacin is as high as that of the comparator drugs in the treatment of ABSSSI, including MRSA-associated infections; furthermore, this antibiotic is as well-tolerated as the comparators.

The Continuing Threat of Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus has been an exceptionally successful pathogen, which is still relevant in modern age-medicine due to its adaptability and tenacity. This bacterium may be a causative agent in a plethora of infections, owing to its abundance (in the environment and in the normal flora) and the variety of virulence factors that it possesses. Methicillin-resistant S. aureus (MRSA) strains—first described in 1961—are characterized by an altered penicillin-binding protein (PBP2a/c) and resistance to all penicillins, cephalosporins, and carbapenems, which makes the β-lactam armamentarium clinically ineffective. The acquisition of additional resistance determinants further complicates their eradication; therefore, MRSA can be considered as the first representative of multidrug-resistant bacteria. Based on 230 references, the aim of this review is to recap the history, the emergence, and clinical features of various MRSA infections (hospital-, community-, and livestock-associated), and to summarize the current advances regarding MRSA screening, typing, and therapeutic options (including lipoglycopeptides, oxazolidinones, anti-MRSA cephalosporins, novel pleuromutilin-, tetracycline- and quinolone-derivatives, daptomycin, fusidic acid, in addition to drug candidates in the development phase), both for an audience of clinical microbiologists and infectious disease specialists.

Comparative In Vitro Activities of New Antibiotics for the Treatment of Skin Infections

Bacterial skin infections result in significant morbidity and have contributed to enhanced health-care resource utilization. The problem is heightened by emerging antimicrobial resistance. Multiple novel agents active against resistant pathogens that cause skin infections-including dalbavancin, tedizolid phosphate, oritavancin, and delafloxacin-have been approved over the past 5 years. Common features of these agents include gram-positive activity and favorable safety. Of these agents, delafloxacin is unique in being active against both gram-positive and gram-negative pathogens that cause skin infections, including those resistant to other antimicrobial agents. It is, therefore, an effective option for the treatment of skin infections.

Analysis of Pooled Phase III Efficacy Data for Delafloxacin in Acute Bacterial Skin and Skin Structure Infections

BACKGROUND

Delafloxacin is an oral or intravenous (IV) antibiotic indicated for the treatment of acute bacterial skin and skin structure infections (ABSSSI), including both gram-positive (including methicillin-resistant Staphylococcus aureus [MRSA]) and gram-negative organisms. Chemically distinct from other quinolones, delafloxacin exhibits enhanced potency, particularly against gram-positive pathogens. The integration of efficacy data across the Phase III ABSSSI studies is presented here and allows for additional examination of results across subgroups.

METHODS

Results of 2 multicenter, randomized, double-blind trials of 1510 adults with ABSSSI were pooled for this analysis. Subjects in the vancomycin arm received 15 mg/kg, plus 1-2 g of aztreonam every 12 hours. Delafloxacin was dosed at 300 mg IV every 12 hours in Study 302; dosing in Study 303 was 300 mg IV every 12 hours for 3 days, with a mandatory, blinded switch to delafloxacin at 450 mg orally every 12 hours. The primary endpoint was objective response (OR), defined as a ≥20% reduction of lesion spread of erythema area at the primary infection site at 48 to 72 hours (±2 hours), in the absence of clinical failure. Investigator-assessed response, based on the resolution of signs and symptoms at follow-up (FU; Day 14 ± 1) and late follow-up (LFU; Day 21- 28), were secondary endpoints.

RESULTS

In the intent-to-treat analysis set, the OR was 81.3% in the delafloxacin arm and 80.7% in the comparator arm (mean treatment difference 0.8%, 95% confidence interval -3.2% to 4.7). Results for OR in the defined subgroups showed delafloxacin to be comparable to vancomycin/aztreonam. Investigator-assessed success was similar at FU (84.7% versus 84.1%) and LFU (82.0% versus 81.7%). Delafloxacin was comparable to vancomycin/aztreonam in the eradication of MRSA, at 98.1% versus 98.0%, respectively, at FU. The frequencies of treatment-emergent adverse events between the groups were similar.

CONCLUSIONS

Overall, IV/oral delafloxacin fixed-dose monotherapy was non-inferior to IV vancomycin/aztreonam combination therapy and was well tolerated in each Phase III study, as well as in the pooled analysis, regardless of endpoint or analysis population.

Profile of a Novel Anionic Fluoroquinolone-Delafloxacin

Fluoroquinolones have been in clinical use for over 50 years with significant efficacy. However, increasing resistance and emergence of some marked adverse events have limited their usage. The most recently approved class member, delafloxacin, is the only available anionic (non-zwitterionic) fluoroquinolone. Its unique molecular structure provides improved in vitro activity against most Gram-positive pathogens, including quinolone-resistant strains, which is further enhanced at acid pH. Delafloxacin shows favorable pharmacological properties, with about 60% bioavailability after oral administration, only mild inhibition of cytochrome P450 3A, and no evidence of cardiac- or phototoxicity in healthy volunteers (tested against positive controls). Its twice daily dosing, suitability for intravenous, oral, or switch dosing, the lack of many clinically significant drug-drug interactions, and acceptable adverse event profile in registration clinical trials supports its use in the treatment of acute bacterial skin and skin structure infections, and potentially in other infections, where resistance to other agents, safety, and/or the need for early discharge is of concern.

Delafloxacin In Vitro Broth Microdilution and Disk Diffusion Antimicrobial Susceptibility Testing Guidelines: Susceptibility Breakpoint Criteria and Quality Control Ranges for an Expanded-Spectrum Anionic Fluoroquinolone

Delafloxacin, a recently approved anionic fluoroquinolone, was tested within an international resistance surveillance program. The in vitro susceptibilities of 7,914 indicated pathogens causing acute bacterial skin and skin structure infections (ABSSSI) were determined using Clinical and Laboratory Standards Institute (CLSI) broth microdilution MIC testing methods. The U.S. Food and Drug Administration (FDA) susceptibility testing breakpoints and quality control ranges for routine broth microdilution and disk diffusion methods were confirmed. The delafloxacin MIC50/90 (% susceptibility) results were as follows: Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA), 0.008/0.25 μg/ml (92.8%); Staphylococcus lugdunensis, 0.016/0.03 μg/ml (99.3%); Streptococcus pyogenes, 0.016/0.03 μg/ml (100.0%); Streptococcus anginosus group, 0.008/0.016 μg/ml (100.0%); Enterococcus faecalis, 0.12/1 μg/ml (66.2%); and Enterobacteriaceae, 0.12/4 μg/ml (69.5%). The FDA clinical breakpoints were used to assess intermethod test agreement between delafloxacin MIC and disk diffusion methods for the indicated pathogens. The intermethod susceptibility test categorical agreement for delafloxacin was acceptable, with only 0.4% very major, false-susceptible errors among S. aureus strains. Across all FDA-indicated species, the selected breakpoints produced only 0.0 to 1.7% rates of serious (very major and major errors) intermethod error. Quality control ranges for these standardized delafloxacin susceptibility test methods were calculated from three multilaboratory (12 total sites) studies for six control organisms. In conclusion, the application of FDA MIC breakpoints for delafloxacin against contemporary (2014 to 2016) isolates of ABSSSI pathogens provides additional support for the use of delafloxacin in the treatment of adults with ABSSSI. Delafloxacin MIC and disk diffusion susceptibility testing methods have been standardized for clinical application, achieving high intermethod categorical agreement.

Efficacy and safety of delafloxacin compared with vancomycin plus aztreonam for acute bacterial skin and skin structure infections: a Phase 3, double-blind, randomized study

Background

Delafloxacin is an investigational anionic fluoroquinolone in development for oral or intravenous administration for the treatment of infections caused by Gram-positive (including MRSA), Gram-negative, atypical and anaerobic organisms.

Objectives

To establish the non-inferiority of delafloxacin compared with vancomycin plus aztreonam for the treatment of acute bacterial skin and skin structure infections and to compare the safety of the two antimicrobials.

Patients and methods

A Phase 3, multicentre, randomized, double-blind, active-controlled study with 660 patients compared delafloxacin 300 mg or vancomycin 15 mg/kg plus aztreonam 2 g each administered twice daily intravenously for 5–14 days. Non-inferiority was evaluated by objective response (≥20% erythema reduction) at 48–72 h after initiation of study drug, investigator subjective assessment of outcome and microbiological responses. Clinical Trials Registration: NCT01811732. EudraCT number: 2012-001767-71.

Results

In the ITT analysis set, the objective response was 78.2% in the delafloxacin arm and 80.9% in the vancomycin/aztreonam arm (mean treatment difference, −2.6%; 95% CI, −8.78% to 3.57%). Investigator-assessed cure was similar between the two groups at follow-up (52.0% versus 50.5%) and late follow-up (70.4% versus 66.6%). Bacterial eradication of MRSA was 100% and 98.5% in the delafloxacin group and the vancomycin/aztreonam group, respectively. Frequency of treatment-emergent adverse events in the delafloxacin and vancomycin/aztreonam groups was similar. Treatment-emergent adverse events leading to study drug discontinuation were higher in the vancomycin/aztreonam group compared with the delafloxacin group (4.3% versus 0.9%).

Conclusions

Delafloxacin, an anionic fluoroquinolone, was statistically non-inferior to vancomycin/aztreonam at 48–72 h following the start of therapy and was well tolerated as monotherapy in the treatment of acute bacterial skin and skin structure infections.