Progress in the Fight Against Multidrug-Resistant Bacteria 2005-2016: Modern Noninferiority Trial Designs Enable Antibiotic Development in Advance of Epidemic Bacterial Resistance.

From a public health perspective, new antibacterial agents should be evaluated and approved for use before widespread resistance to existing agents emerges. However, for multidrug-resistant pathogens, demonstration of superior efficacy of a new agent over a current standard-of-care agent is routinely feasible only when epidemic spread of these dangerous organisms has already occurred. One solution to enable proactive drug development is to evaluate new antibiotics with improved in vitro activity against MDR pathogens using recently updated guidelines for active control, noninferiority trials of selected severe infections caused by more susceptible pathogens. Such trials are feasible because they enroll patients with infections due to pathogens with a "usual drug resistance" phenotype that will be responsive to widely registered standard-of-care comparator antibiotics. Such anticipatory drug development has constructively reshaped the antibiotic pipeline and offers the best chance of making safe and efficacious antibiotics available to the public ahead of epidemic resistance.

A randomized, double-blind, comparative study to assess the safety and efficacy of topical retapamulin ointment 1% versus oral linezolid in the treatment of secondarily infected traumatic lesions and impetigo due to methicillin-resistant Staphylococcus aureus.

OBJECTIVE: To evaluate the clinical and bacteriological efficacy of topical retapamulin ointment 1% versus oral linezolid in the treatment of patients with secondarily infected traumatic lesions (SITLs; excluding abscesses) or impetigo due to methicillin-resistant Staphylococcus aureus (MRSA). DESIGN: A randomized, double-blind, double-dummy, multicenter, comparative study (NCT00852540). SETTING: Patients recruited from 36 study centers in the United States. PATIENTS: Patients 2 months or older with SITL (including secondarily infected lacerations or sutured wounds) or impetigo (bullous and nonbullous) suitable for treatment with a topical antibiotic, with a total Skin Infection Rating Scale score of 8 or greater, including a pus/exudate score of 3 or greater. INTERVENTIONS: Patients received retapamulin ointment 1% (plus oral placebo), twice daily for 5 days or oral linezolid (plus placebo ointment) 2 or 3 times daily for 10 days. MAIN OUTCOME MEASURE: Primary end point: clinical response (success/failure) at follow-up in patients with MRSA at baseline (per-protocol population). Secondary efficacy end points: clinical and microbiologic response and outcome at follow-up and end of therapy; therapeutic response at follow-up. MAIN RESULTS: The majority of patients had SITL (70.4% [188/267] and 66.4% [91/137] in the retapamulin and linezolid groups, respectively; intent-to-treat clinical population). Clinical success rate at follow-up was significantly lower in the retapamulin versus the linezolid group (63.9% [39/61] vs 90.6% [29/32], respectively; difference in success rate -26.7%; 95% CI, -45.7 to -7.7). CONCLUSIONS: Clinical success rate at follow-up in the per-protocol MRSA population was significantly lower in the retapamulin versus the linezolid group. It could not be determined whether this was related to study design, bacterial virulence, or retapamulin activity.

Systematic review and meta-analysis of antimicrobial treatment effect estimation in complicated urinary tract infection.

Noninferiority trial design and analyses are commonly used to establish the effectiveness of a new antimicrobial drug for treatment of serious infections such as complicated urinary tract infection (cUTI). A systematic review and meta-analysis were conducted to estimate the treatment effects of three potential active comparator drugs for the design of a noninferiority trial. The systematic review identified no placebo trials of cUTI, four clinical trials of cUTI with uncomplicated urinary tract infection as a proxy for placebo, and nine trials with reports of treatment effect estimates for doripenem, levofloxacin, or imipenem-cilastatin. In the meta-analysis, the primary efficacy endpoint of interest was the microbiological eradication rate at the test-of-cure visit in the microbiological intent-to-treat population. The estimated eradication rates and corresponding 95% confidence intervals (CI) were 31.8% (26.5% to 37.2%) for placebo, 81% (77.7% to 84.2%) for doripenem, 79% (75.9% to 82.2%) for levofloxacin, and 80.5% (71.9% to 89.1%) for imipenem-cilastatin. The treatment effect estimates were 40.5% for doripenem, 38.7% for levofloxacin, 34.7% for imipenem-cilastatin, and 40.8% overall. These treatment effect estimates can be used to inform the design and analysis of future noninferiority trials in cUTI study populations.

Disposition and metabolism of GSK2251052 in humans: a novel boron-containing antibiotic.

(S)-3-(Aminomethyl)-7-(3-hydroxypropoxy)-1-hydroxy-1,3-dihydro-2,1-benzoxaborole (GSK2251052) is a novel boron-containing antibiotic that inhibits bacterial leucyl tRNA synthetase, and that has been in development for the treatment of serious Gram-negative infections. In this study, six healthy adult male subjects received a single i.v. dose of [¹4C]GSK2251052, 1500 mg infused over 1 hour. Blood, urine, and feces were collected over an extended period of 14 days, and accelerator mass spectrometry was used to quantify low levels of radioactivity in plasma at later time points to supplement the less-sensitive liquid scintillation counting technique. An excellent mass balance recovery was achieved representing a mean total of 98.2% of the dose, including 90.5% recovered in the urine. Pharmacokinetic analysis demonstrated that radioactivity was moderately associated with the blood cellular components, and together with GSK2251052, both were highly distributed into tissues. The parent compound had a much shorter half-life than total radioactivity in plasma, approximately 11.6 hours compared with 96 hours. GSK2251052 and its major metabolite M3, which resulted from oxidation of the propanol side chain to the corresponding carboxylic acid, comprised the majority of the plasma radioactivity, 37 and 53% of the area under the plasma versus time concentration curve from time zero to infinity, respectively. Additionally, M3 was eliminated renally, and was demonstrated to be responsible for the long plasma radioactivity elimination half-life. A combination of in vitro metabolism experiments and a pharmacokinetic study in monkeys with the inhibitor 4-methylpyrazole provided strong evidence that alcohol dehydrogenase, potentially in association with aldehyde dehydrogenase, is the primary enzyme involved in the formation of the M3 metabolite.

The safety and efficacy of topical retapamulin ointment versus placebo ointment in the treatment of secondarily infected traumatic lesions: a randomized, double-blind superiority study.

OBJECTIVE: To evaluate whether retapamulin 1% is clinically superior to a placebo in the treatment of patients with secondarily infected traumatic lesions. DESIGN: The study was a double-blind, placebo-controlled, parallel-group, phase 3 study. SETTING: Patients were recruited from 5 countries. PATIENTS: The aforementioned patients were all 2 months or older and diagnosed with secondarily infected traumatic lesions. INTERVENTIONS: Study medication was applied twice daily for 5 days. MAIN OUTCOME MEASURES: Primary end point: clinical response (success/failure) at follow-up. Secondary efficacy end points included clinical and microbiological outcomes at end of therapy (on days 7-9); microbiological and therapeutic responses at follow-up. MAIN RESULTS: A total of 508 patients were recruited for the study; 359 patients were included in the primary efficacy analysis population (246 received retapamulin; 113 received the placebo). Secondarily infected abrasions were the most common secondarily infected traumatic lesions present (56.3%), Staphylococcus aureus being the most frequently isolated pathogen at baseline (60.1%); 15.1% infections were methicillin-resistant. At follow-up, patients receiving retapamulin had higher clinical success rates than those receiving the placebo (74.8% vs 66.4%, respectively) in the primary efficacy analysis population; however, the treatment difference was not statistically significant (8.4%; 95% confidence interval, -1.6 to 18.4). The proportion of patients experiencing adverse events, which were typically mild or moderate in severity, was similar between the retapamulin (5.6%, 19/342) and placebo groups (4.8%, 8/165). CONCLUSION: Clinical success rates were higher with retapamulin versus placebo in the treatment of patients with secondarily infected traumatic lesions, but the difference between treatment groups was not significant. Retapamulin was well tolerated.

Efficacy and safety of a phospholipid emulsion (GR270773) in Gram-negative severe sepsis: results of a phase II multicenter, randomized, placebo-controlled, dose-finding clinical trial.

OBJECTIVE: To assess the survival benefit and safety profile of low-dose (850 mg/kg) and high-dose (1350 mg/kg) phospholipid emulsion vs. placebo administered as a continuous 3-day infusion in patients with confirmed or suspected Gram-negative severe sepsis. Preclinical and ex vivo studies show that lipoproteins bind and neutralize endotoxin, and experimental animal studies demonstrate protection from septic death when lipoproteins are administered. Endotoxin neutralization correlates with the amount of phospholipid in the lipoprotein particles. DESIGN: A three-arm, randomized, blinded, placebo-controlled trial. SETTING: Conducted at 235 centers worldwide between September 2004 and April 2006. PATIENTS: A total of 1379 patients participated in the study, 598 patients received low-dose phospholipid emulsion, and 599 patients received placebo. The high-dose phospholipid emulsion arm was stopped, on the recommendation of the Independent Data Monitoring Committee, due to an increase in life-threatening serious adverse events at the fourth interim analysis and included 182 patients. MEASUREMENTS AND MAIN RESULTS: A 28-day all-cause mortality and new-onset organ failure. There was no significant treatment benefit for low- or high-dose phospholipid emulsion vs. placebo for 28-day all-cause mortality, with rates of 25.8% (p = .329), 31.3% (p = .879), and 26.9%, respectively. The rate of new-onset organ failure was not statistically different among groups at 26.3%, 31.3%, 20.4% with low- and high-dose phospholipid emulsion, and placebo, respectively (one-sided p = .992, low vs. placebo; p = .999, high vs. placebo). Of the subjects treated, 45% had microbiologically confirmed Gram-negative infections. Maximal changes in mean hemoglobin levels were reached on day 10 (-1.04 g/dL) and day 5 (-1.36 g/dL) with low- and high-dose phospholipid emulsion, respectively, and on day 14 (-0.82 g/dL) with placebo. CONCLUSIONS: Treatment with phospholipid emulsion did not reduce 28-day all-cause mortality, or reduce the onset of new organ failure in patients with suspected or confirmed Gram-negative severe sepsis.