Efficacy of delafloxacin versus moxifloxacin against atypical bacterial respiratory pathogens in adults with community-acquired bacterial pneumonia (CABP): Data from the Delafloxacin Phase 3 CABP Trial.

OBJECTIVES: To report atypical pathogens from clinical trial data comparing delafloxacin to moxifloxacin in the treatment of adults with community-acquired bacterial pneumonia (CABP). METHODS: Multiple diagnostic methods were employed to diagnose atypical infections including culture, serology, and urinary antigen. RESULTS: The microbiological intent-to-treat (MITT) population included 520 patients; 30% had an atypical bacterial pathogen identified (156/520). Overall, 13.1% (68/520) had a monomicrobial atypical infection and 2.3% (12/520) had polymicrobial all-atypical infections. Among patients with polymicrobial infections, Streptococcus pneumoniae was the most frequently occurring co-infecting organism and Chlamydia pneumoniae was the most frequently occurring co-infecting atypical organism. For Mycoplasma pneumoniae and Legionella pneumophila, serology yielded the highest number of diagnoses. Delafloxacin and moxifloxacin had similar in vitro activity against M. pneumoniae and delafloxacin had greater activity against L. pneumophila. Two macrolide-resistant M. pneumoniae isolates were recovered. No fluoroquinolone-resistant M. pneumoniae were isolated. The rates of microbiological success (documented or presumed eradication) at test-of-cure were similar between the delafloxacin and moxifloxacin groups. There was no evidence of a correlation between minimum inhibitory concentration (MIC) and outcome; a high proportion of favorable outcomes was observed across all delafloxacin baseline MICs. CONCLUSIONS: Delafloxacin may be considered a treatment option as monotherapy for CABP in adults, where broad-spectrum coverage including atypical 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.

Question-Based Collaborative Learning for Constructive Curricular Alignment.

INTRODUCTION: We designed a curriculum mapping tool which enables medical students to access intended learning outcomes (ILOs) on their iPads in the workplace. Students were encouraged to use the online curriculum map in a specially planned teaching session: question-based collaborative learning (QBCL). The aim of the session was to empower medical students to constructively align their experiential learning with the learning outcomes of the undergraduate curriculum. In doing so, our session aimed to provide students with a greater understanding of the curriculum, improve their insights into assessment and their question-writing abilities. METHODS: The QBCL pre-session preparation involved reviewing a patient with a presentation that aligned to the year-specific ILOs. During a 150 minute QBCL session, students received training on how to write high quality multiple choice questions (MCQs) delivered by a faculty member of Imperial College School of Medicine. They then worked collaboratively in groups and created MCQs based on their clinical encounters. Their questions were tagged to the relevant learning objective and submitted online via the curriculum map. The student-generated MCQs were analyzed using an adjusted version of Bloom's taxonomy. We also conducted a quantitative evaluation of the session. RESULTS: One hundred and sixty-three questions were submitted, with 81% of questions being tagged to ILOs considered to show evidence of learning consistent with the "Apply" tier of Bloom's taxonomy. The majority of students agreed that the session was interactive (80%), thought-provoking (77%) and improved their team-working skills (70%). It gave them a greater understanding of the undergraduate curriculum (65%), improved their question-writing and insight into assessments (76%), and provided an opportunity to learn from their peers (86%). Students agreed that this session covered a variety of cases (82%) and deepened their understanding of medical conditions and presentations (87%). CONCLUSION: We encouraged students to actively interact with the curriculum map. Students were able to achieve their own constructive alignment by writing assessment items based on real patients and linking them to the appropriate intended learning outcomes.

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. 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 (ß-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 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 Pharmacokinetics of Sulfobutylether-ß-Cyclodextrin in Patients With Varying Degrees of Renal Impairment.

Delafloxacin, a fluoroquinolone, has activity against Gram-positive organisms including methicillin-resistant S aureus and fluoroquinolone-susceptible and -resistant Gram-negative organisms. The intravenous formulation of delafloxacin contains the excipient sulfobutylether-ß-cyclodextrin (SBECD), which is eliminated by renal filtration. This study examined the pharmacokinetics and safety of SBECD after single intravenous (IV) infusions in subjects with renal impairment. The study was an open-label, parallel-group, crossover study in subjects with normal renal function or mild, moderate, or severe renal impairment, and those with end-stage renal disease undergoing hemodialysis. Subjects received 300 mg delafloxacin IV or placebo IV, containing 2400 mg SBECD, in 2 periods separated by ≥14-day washouts. SBECD total clearance decreased with decreasing renal function, with a corresponding increase in area under the concentration-time curve (AUC0-∞ ). After IV delafloxacin 300 mg administration, SBECD mean total clearance was 6.28 and 1.24 L/h, mean AUC0-∞ was 387 and 2130 h·µg/mL, and mean renal clearance was 5.36 and 1.14 L/h in normal and severe renal subjects, respectively. Similar values were obtained after IV placebo administration. In subjects with end-stage renal disease, delafloxacin 300 mg IV produced mean SBECD AUC0-48 values of 2715 and 7861 h·µg/mL when dosed before and after hemodialysis, respectively. Total SBECD clearance exhibited linear relationships to estimated glomerular filtration rate and creatinine clearance. Single doses of IV delafloxacin 300 mg and IV placebo were well tolerated in all groups. In conclusion, decreasing renal function causes reduced SBECD clearance and increased exposures, but SBECD continues to exhibit a good safety and tolerability profile in IV formulations.

Pharmacokinetics of Intravenous Delafloxacin in Patients With End-Stage Renal Disease.

This was an open-label, parallel-group, crossover study that examined the pharmacokinetics and safety of delafloxacin, an anionic fluoroquinolone, after a single intravenous infusion in subjects with end-stage renal disease (ESRD; creatinine clearance <15 mL/min) undergoing hemodialysis compared with healthy subjects. Subjects received 300 mg delafloxacin containing sulfobutylether-ß-cyclodextrin in 2 periods separated by ≥14-day washouts. Blood and urine samples were collected, and pharmacokinetic parameters were calculated using noncompartmental methods. The mean total exposure (area under the curve) of delafloxacin was about 2.1 and 2.6 higher for subjects with ESRD compared to healthy subjects when dosed 1 hour before or 1 hour after hemodialysis, respectively. Compared to subjects with normal renal function, the maximum exposure to delafloxacin was 13% and 33% higher for ESRD subjects given delafloxacin 1 hour before and 1 hour after hemodialysis, respectively. The mean clearance was 13.7 L/h for healthy subjects and was lower for subjects with ESRD when given before (7.39 L/h) or after (5.69 L/h) hemodialysis. The clearance of delafloxacin in dialysate was 4.74 L/h with about 19.2% of the delafloxacin dose recovered after a 4-hour dialysis session. Delafloxacin was well tolerated in both healthy and ESRD subjects, with diarrhea being the most reported treatment-emergent adverse event.

Delafloxacin Pharmacokinetics in Subjects With Varying Degrees of Renal Function.

Delafloxacin, a fluoroquinolone, has activity against gram-positive organisms including methicillin-resistant Staphylococcus aureus and fluoroquinolone-susceptible and -resistant gram-negative organisms. This study was conducted to determine delafloxacin pharmacokinetics after a single intravenous infusion or oral dose administration in subjects with varying degrees of renal function. The study was an open-label, parallel-group crossover study in subjects with normal renal function or with mild, moderate, or severe renal impairment. Subjects received 300 mg delafloxacin intravenously, placebo intravenously, and 400 mg delafloxacin orally in 3 periods separated by ≥14-day washouts. Blood and urine pharmacokinetic parameters were calculated using noncompartmental methods. Delafloxacin total clearance decreased with decreasing renal function, with a corresponding increase in AUC0-∞ . After intravenous administration, mean total clearance was 13.7 and 7.07 L/h, and mean AUC0-∞ was 22.6 and 45.0 µg·h/mL in normal and severe renal subjects, respectively. Mean renal clearance as determined by urinary excretion was 6.03 and 0.44 L/h in normal and severe renal impairment subjects, respectively. Total clearance exhibited linear relationships to eGFR and CLCR . Similar observations were found after oral administration of delafloxacin. Single doses of delafloxacin 300 mg intravenously and 400 mg orally were well tolerated in all groups. In conclusion, renal insufficiency has an effect on delafloxacin clearance; a dosing adjustment for intravenous dosing is warranted for patients with severe renal impairment (eGFR < 30 mL/min).

The Pharmacokinetics of the CYP3A Substrate Midazolam After Steady-state Dosing of Delafloxacin.

PURPOSE: Delafloxacin is a novel anionic fluoroquinolone in Phase III development for the treatment of serious skin infections. The objective of this study was to evaluate the effects of delafloxacin on the pharmacokinetics of midazolam, a cytochrome P450 (CYP) 3A substrate. METHODS: CYP3A activity using midazolam as a probe was assessed before and after multiple doses of delafloxacin to reach steady state. In this nonrandomized, open-label, single-sequence, Phase I study, 22 healthy male and female subjects were administered a single 5-mg oral dose of midazolam on days 1 and 8, with oral delafloxacin 450 mg every 12 hours administered from days 3 to 8. Full pharmacokinetic profiles were obtained on days 1 and 8 (midazolam and 1-hydroxymidazolam) and days 3 and 7 (delafloxacin). FINDINGS: The geometric mean ratios (90% CIs) for AUC0-∞ and Cmax of midazolam coadministered with delafloxacin versus midazolam alone were 89.4 (83.2-96.0) and 93.6 (83.7-104.6). Similarly, the geometric ratio for the AUC0-∞ of 1-hydroxymidazolam, the primary metabolite of midazolam, was 105.7 (97.7-114.3); the ratio of Cmax was not equivalent at 116.1 (101.7-132.4), which was outside the CI of 80% to 125%. Multiple doses of oral delafloxacin for 6 days were generally well tolerated. IMPLICATIONS: Steady-state dosing of delafloxacin produced no significant changes in midazolam pharmacokinetics, except for a small but not clinically relevant change in the Cmax of 1-hydroxymidazolam. ClinicalTrials.gov identifier: NCT02505997.

Clinical Pharmacology of Delafloxacin in Patients With Hepatic Impairment.

Delafloxacin is a novel anionic fluoroquinolone with robust activity against Gram-positive, Gram-negative, atypical, and anaerobic bacteria, including methicillin-resistant S aureus. Delafloxacin is currently being studied for the treatment of acute bacterial skin and skin structure infections and community-acquired pneumonia. This was a phase 1, open-label pharmacokinetic and safety study of a single intravenous dose of 300 mg delafloxacin in subjects with mild, moderate, and severe hepatic impairment (Child-Pugh class A, B, and C, respectively) compared with matched healthy controls. The effects of hepatic impairment were assessed by ANOVA of log-transformed values for AUC0-∞ , Cmax , and systemic clearance, with hepatic group as a fixed effect. Mean AUC0-∞ and Cmax in each impairment group were not significantly different from those of the pooled healthy subjects (P > 0.05). The 90% confidence interval (CI) of the percentage ratios of least-squares means of AUC0-∞ did not indicate significant differences between the impairment groups and pooled healthy controls: Child-Pugh class A (mild) 114.4 (CI: 95.6, 137.0), Child-Pugh class B (moderate) 114.8 (CI: 95.9, 137.4), and Child-Pugh class C (severe) 115.1 (CI: 96.1, 137.8). A single IV infusion of delafloxacin was generally well tolerated in all treatment groups. The exposure and clearance of delafloxacin in subjects with mild, moderate, or severe hepatic impairment did not significantly differ from those of pooled, matched healthy subjects. Based on these pharmacokinetic data, dose adjustment of delafloxacin in the presence of hepatic impairment is not needed.

Safety, Tolerability, and Pharmacokinetic Properties of Intravenous Delafloxacin After Single and Multiple Doses in Healthy Volunteers.

PURPOSE: The objective of this report was to determine the pharmacokinetic properties, safety, and tolerability of single and multiple doses of intravenous delafloxacin. In addition, the absolute bioavailability (BA) of the 450-mg tablet formulation of delafloxacin was determined. METHODS: Three clinical trials are summarized. The first study was a randomized, double-blind, placebo-controlled, single- (300, 450, 600, 750, 900, and 1200 mg) ascending-dose study of IV delafloxacin in 62 (52 active, 10 placebo) healthy volunteers. The second study was a randomized, double-blind, placebo-controlled study of IV delafloxacin (300 mg) given as a single dose on day 1, followed by twice-daily dosing on days 2 through 14; 12 (8 active, 4 placebo) healthy volunteers were enrolled. The third study was an open-label, randomized, 2-period, 2-sequence crossover study in which 56 healthy volunteers were randomly assigned to 1 of 2 sequences of a single oral dose of delafloxacin (450-mg tablet) or IV delafloxacin (300 mg). Serial blood samples were collected, and plasma pharmacokinetic parameters of delafloxacin were calculated. FINDINGS: Delafloxacin Cmax values increased proportionally with increasing single IV dose for the dose range of 300 to 1200 mg, whereas the AUC values increased more than proportionally to dose for the same dose range. The mean terminal half-life of delafloxacin was approximately 12 hours (ranging from 8 to 17 hours). The volume of distribution (Vd) at steady state was approximately 35 L, which is similar to the volume of total body water. There was minimal accumulation of delafloxacin after twice-daily IV administration of 300 mg with an accumulation ratio of 1.09. The delafloxacin total exposure after a single 1-hour IV infusion of 300 mg and a single oral dose of a 450-mg tablet were equivalent with geometric least square mean ratio (90% CI) of 0.8768 (0.8356-0.9200) for AUC0-∞ and 0.8445 (0.8090-0.8815) for AUC0-t, respectively. The Cmax values of delafloxacin were not equivalent for the 2 formulations with a ratio (90% CI) of 0.5516 (0.5150-0.5908), respectively. The mean absolute bioavailability of delafloxacin was 58.8%. IMPLICATIONS: Delafloxacin was well tolerated in healthy volunteers after single and multiple IV doses. The total systemic exposure to IV (300 mg) and oral (450 mg) delafloxacin is comparable, supporting that a switch between the 2 formulations is appropriate.

Single and Multiple Ascending-dose Studies of Oral Delafloxacin: Effects of Food, Sex, and Age.

PURPOSE: The objective of this report is describe the results of 2 studies that examined the pharmacokinetic parameters, safety profile, and tolerability of single and multiple ascending doses of oral delafloxacin and the effects of food, sex, and age on oral delafloxacin pharmacokinetic parameters, safety profile, and tolerability. METHODS: The first study contained 3 parts and used unformulated delafloxacin in a capsule. Part 1 was a randomized, double-blind, placebo-controlled, single (50, 100, 200, 400, 800, 1200, and 1600 mg) ascending-dose study of oral delafloxacin in healthy men. Part 2 was a single-dose crossover study in which 20 men received 250 mg delafloxacin with or without food. Part 2 also included a parallel group, double-blind, placebo-controlled study in 16 women and 16 elderly men and women who were randomized (3:1) to receive 250 mg delafloxacin or placebo. Part 3 was a randomized, double-blind, placebo-controlled, multiple (100, 200, 400, 800, 1200 mg once daily for 5 days) ascending-dose study of oral delafloxacin in healthy men. The second study was a single-dose, randomized, 3-period crossover study in which participants received 900 mg delafloxacin (2 × 450-mg tablets) under fasted conditions, with a high-fat meal, or fasted with a high-fat meal 2 hours after dosing. Serial blood samples were collected, and plasma pharmacokinetic parameters of delafloxacin were determined. FINDINGS: Delafloxacin Cmax and AUC0-∞ increased with increasing oral dose over the dose range of 50 to 1600 mg. The increases in delafloxacin AUC0-∞ were dose proportional at doses of ≥200 mg. Steady state was reached by day 3 of dosing with minimal accumulation of delafloxacin. The Cmax of delafloxacin was decreased slightly in the presence of food. No sex difference in delafloxacin pharmacokinetic parameters was observed. In the elderly men and women, mean delafloxacin Cmax and AUC0-∞ were 35% higher than observed for young adults, which could be partially explained by a decrease in the creatinine clearance in the elderly men and women. Delafloxacin was well tolerated at the tested doses, with gastrointestinal adverse effects observed more commonly at doses ≥1200 mg. IMPLICATIONS: 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).

A randomized, double-blind, Phase 2 study to evaluate subjective and objective outcomes in patients with acute bacterial skin and skin structure infections treated with delafloxacin, linezolid or vancomycin.

OBJECTIVES: Delafloxacin 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). METHODS: In 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. RESULTS: Cure 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/m(2); 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. CONCLUSIONS: These data show that delafloxacin is effective in the treatment of ABSSSIs and is well tolerated.

Disposition, metabolism and mass balance of delafloxacin in healthy human volunteers following intravenous administration.

1. The pharmacokinetics and disposition of delafloxacin was investigated following a single intravenous (300 mg, 100 µCi) dose to healthy male subjects. 2. Mean Cmax, AUC0-∞, Tmax and t1/2 values for delafloxacin were 8.98 µg/mL, 21.31 µg h/mL, 1 h and 2.35 h, respectively, after intravenous dosing. 3. Radioactivity was predominantly excreted via the kidney with 66% of the radioactive dose recovered in the urine. Approximately 29% of the radioactivity was recovered in the faeces, giving an overall mean recovery of 94% administered radioactivity. 4. The predominant circulating components were identified as delafloxacin and a direct glucuronide conjugate of delafloxacin.

A thorough QT study to evaluate the effects of therapeutic and supratherapeutic doses of delafloxacin on cardiac repolarization.

A randomized, double-blind, placebo-controlled, 4-period crossover study was conducted in 52 healthy adults to assess the effect of delafloxacin on the corrected QT (QTc) interval. The QT interval, corrected for heart rate using Fridericia's formula (QTcF), was determined predose and at 0.5, 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 4, 5, 6, 12, 18, and 24 h after dosing with delafloxacin at 300 mg intravenously (i.v.; therapeutic), delafloxacin at 900 mg i.v. (supratherapeutic), moxifloxacin at 400 mg orally (p.o.; positive control), and placebo. The pharmacokinetic profile of delafloxacin was also evaluated. At each time point after delafloxacin administration, the upper limit of the 90% confidence interval (CI) for the placebo-corrected change from the predose baseline in QTcF (ΔΔQTcF) was less than 10 ms (maximum, 3.9 ms at 18 h after dosing), indicating an absence of a clinically meaningful increase in the QTc interval. The lower limit of the 90% CI of ΔΔQTcF for moxifloxacin versus placebo was longer than 5 ms at all 5 time points selected for assay sensitivity analysis, demonstrating that the study was adequately sensitive to assess QTc prolongation. There was no positive relationship between delafloxacin plasma concentrations and ΔΔQTcF. Treatment-emergent adverse events (AEs) were more frequent among subjects receiving a single supratherapeutic dose of 900 mg delafloxacin. There were no deaths, serious AEs, or AEs leading to study discontinuation and no clinically meaningful abnormalities in laboratory values or vital signs observed at any time point after any dose of the study drug.

A randomized phase 2 study comparing two doses of delafloxacin with tigecycline in adults with complicated skin and skin-structure infections.

BACKGROUND: A randomized, double-blind, multicenter trial was done to compare two doses of delafloxacin with tigecycline in patients with various complicated skin and skin-structure infections (wound infections following surgery, trauma, burns, or animal/insect bites, abscesses, and cellulitis). METHODS: Patients were randomized 1:1:1 to receive delafloxacin 300mg intravenous (IV) every 12h, delafloxacin 450mg IV every 12h, or tigecycline 100mg IV×1, followed by 50mg IV every 12h; randomization was stratified by infection type. Duration of therapy was 5-14 days. The primary efficacy analysis, performed on the clinically evaluable (CE) population at the test-of-cure (TOC) visit (14-21 days after the final dose of study drug), compared clinical response rates in the delafloxacin and tigecycline arms. Clinical response rates in the two delafloxacin arms were also compared. RESULTS: Among CE patients, clinical cure rates at TOC visit were similar in the delafloxacin and tigecycline arms (94.3%, 92.5%, and 91.2%, respectively in delafloxacin 300-mg, delafloxacin 450-mg, and tigecycline arms). Overall, the most frequent adverse events were nausea, vomiting, and diarrhea; the 300-mg delafloxacin arm was the best-tolerated regimen. CONCLUSIONS: Delafloxacin was similarly effective as tigecycline for a variety of complicated skin and skin-structure infections and was well tolerated. (Clinicaltrials.gov NCT 0719810).

R chi-01, a new family of oxazolidinones that overcome ribosome-based linezolid resistance.

New and improved antibiotics are urgently needed to combat the ever-increasing number of multidrug-resistant bacteria. In this study, we characterized several members of a new oxazolidinone family, R chi-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 chi-01 family displace, more effectively than linezolid, compounds known to bind to the ribosomal A site. We also monitored binding by assessing whether R chi-01 compounds protect U2585 (Escherichia coli numbering), a nucleotide that influences peptide bond formation and peptide release, from chemical modification by carbodiimide. The R chi-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 chi-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 chi-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 chi-01 family of compounds is currently undergoing clinical trials.

In vitro activities of the Rx-01 oxazolidinones against hospital and community pathogens.

Rx-01_423 and Rx-01_667 are two members of the family of oxazolidinones that were designed using a combination of computational and medicinal chemistry and conventional biological techniques. The compounds have a two- to eightfold-improved potency over linezolid against serious gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), multidrug-resistant streptococci, and vancomycin-resistant enterococci. This enhanced potency extends to the coverage of linezolid-resistant gram-positive microbes, especially multidrug-resistant enterococci and pneumococci. Compounds from this series expand the spectrum compared with linezolid to include fastidious gram-negative organisms like Haemophilus influenzae and Moraxella catarrhalis. Like linezolid, the Rx-01 compounds are bacteriostatic against MRSA and enterococci but are generally bactericidal against S. pneumoniae and H. influenzae.