BackgroundDelafloxacin 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.ObjectivesTo 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 methodsA 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.ResultsIn 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%).ConclusionsDelafloxacin, 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.

ObjectivesDelafloxacin is an investigational anionic fluoroquinolone being developed to treat infections caused by Gram-positive and -negative organisms. This clinical trial evaluated the efficacy and safety of delafloxacin in the treatment of acute bacterial skin and skin structure infections (ABSSSIs).MethodsIn a double-blind, Phase 2 trial, 256 patients were randomized (1 : 1 : 1) to 300 mg of delafloxacin, 600 mg of linezolid or 15 mg/kg vancomycin (actual body weight), each administered intravenously twice daily for 5–14 days. Randomization was stratified by infection category. The primary endpoint was the investigator's assessment of cure, defined as complete resolution of baseline signs and symptoms at follow-up. Secondary endpoints included reductions in the total areas of erythema and induration and assessments of bacterial eradication. This trial has been registered at ClinicalTrials.gov under registration number NCT01283581.ResultsCure rates were significantly greater with delafloxacin versus vancomycin (mean difference: −16.3%; 95% CI, −30.3% to −2.3%; P = 0.031); differences were significant for obese patients (BMI ≥30 kg/m2; mean difference: −30.0%; 95% CI, −50.7% to −9.3%; P = 0.009), but not for non-obese patients. Cure rates with delafloxacin and linezolid were similar. Using digital measurement, the percentage decrease in total erythema area was significantly greater with delafloxacin versus vancomycin at follow-up (−96.4% versus −84.5%; P = 0.028). There were no differences in bacterial eradication among the treatment groups. The most frequently reported treatment-emergent adverse events were nausea, diarrhoea and vomiting.ConclusionsThese data show that delafloxacin is effective in the treatment of ABSSSIs and is well tolerated.

This phase 3 trial in acute bacterial skin and skin structure infections showed IV followed by oral delafloxacin to be noninferior to IV vancomycin/aztreonam combination therapy and well tolerated. Oral delafloxacin appears to maintain the initial response with IV delafloxacin.

Delafloxacin was similarly effective as tigecycline for a variety of complicated skin and skin-structure infections and was well tolerated. (Clinicaltrials.gov NCT 0719810).

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New and improved antibiotics are urgently needed to combat the ever-increasing number of multidrugresistant bacteria. In this study, we characterized several members of a new oxazolidinone family, R-01. This antibiotic family is distinguished by having in vitro and in vivo activity against hospital-acquired, as well as community-acquired, pathogens. We compared the 50S ribosome binding affinity of this family to that of the only marketed oxazolidinone antibiotic, linezolid, using chloramphenicol and puromycin competition binding assays. The competition assays demonstrated that several members of the R-01 family displace, more effectively than linezolid, compounds known to bind to the ribosomal A site. We also monitored binding by assessing whether R-01 compounds protect U2585 (Escherichia coli numbering), a nucleotide that influences peptide bond formation and peptide release, from chemical modification by carbodiimide. The R-01 oxazolidinones were able to inhibit translation of ribosomes isolated from linezolid-resistant Staphylococcus aureus at submicromolar concentrations. This improved binding corresponds to greater antibacterial activity against linezolid-resistant enterococci. Consistent with their ribosomal A-site targeting and greater potency, the R-01 compounds promote nonsense suppression and frameshifting to a greater extent than linezolid. Importantly, the gain in potency does not impact prokaryotic specificity as, like linezolid, the members of the R-01 family show translation 50% inhibitory concentrations that are at least 100-fold higher for eukaryotic than for prokaryotic ribosomes. This new family of oxazolidinones distinguishes itself from linezolid by having greater intrinsic activity against linezolid-resistant isolates and may therefore offer clinicians an alternative to overcome linezolid resistance. A member of the R-01 family of compounds is currently undergoing clinical trials.

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Delafloxacin exhibits linear pharmacokinetic parameters that reached steady state after 3 days of daily oral dosing with minimal accumulation. Delafloxacin was well tolerated throughout both studies, with gastrointestinal effects observed at the higher doses (≥1200 mg).