Background: Increasing antimicrobial resistance among pathogens that cause complicated intraabdominal infections (cIAIs) supports the development of new antimicrobials. Eravacycline, a novel member of the fluorocycline family, is active against multidrug-resistant bacteria including extended-spectrum β-lactamase (ESBL) and carbapenem-resistant Enterobacteriaceae. Methods: IGNITE4 was a prospective, randomized, double-blind trial. Hospitalized patients with cIAI received either eravacycline 1 mg/kg every 12 hours or meropenem 1 g every 8 hours intravenously for 4–14 days. The primary objective was to demonstrate statistical noninferiority (NI) in clinical cure rates at the test-of-cure visit (25–31 days from start of therapy) in the microbiological intent-to-treat population using a NI margin of 12.5%. Microbiological outcomes and safety were also evaluated. Results: Eravacycline was noninferior to meropenem in the primary endpoint (177/195 [90.8%] vs 187/205 [91.2%]; difference, –0.5%; 95% confidence interval [CI], –6.3 to 5.3), exceeding the prespecified margin. Secondary endpoints included clinical cure rates in the modified ITT population (231/250 [92.4%] vs 228/249 [91.6%]; difference, 0.8; 95% CI, –4.1, 5.8) and the clinically evaluable population (218/225 [96.9%] vs 222/231 [96.1%]; (difference, 0.8; 95% CI –2.9, 4.5). In patients with ESBL-producing Enterobacteriaceae, clinical cure rates were 87.5% (14/16) and 84.6% (11/13) in the eravacycline and meropenem groups, respectively. Eravacycline had relatively low rates of adverse events for a drug of this class, with less than 5%, 4%, and 3% of patients experiencing nausea, vomiting, and diarrhea, respectively. Conclusions: Treatment with eravacycline was noninferior to meropenem in adult patients with cIAI, including infections caused by resistant pathogens. Clinical Trials Registration: NCT01844856.

Acute bacterial skin and skin-structure infections are associated with substantial morbidity and health care costs. Omadacycline, an aminomethylcycline antibiotic that can be administered once daily either orally or intravenously, is active against pathogens that commonly cause such infections, including antibiotic-resistant strains.

In a randomized, double-blind, controlled trial, 546 patients with complicated skin and skin structure infections received tigecycline 100 mg/day (a 100-mg initial dose and then 50 mg intravenously twice daily) or the combination of vancomycin 2 g/day (1 g intravenously twice daily) and aztreonam 4 g/day (2 g intravenously twice daily) for up to 14 days. The primary end point was the clinical response in the clinical modified intent-to-treat (c-mITT) and clinically evaluable (CE) populations at the test-of-cure visit 12 to 92 days after the last dose. The microbiologic response at the test-of-cure visit was also assessed. Safety was assessed by physical examination, laboratory results, and adverse event reporting. Five hundred twenty patients were included in the c-mITT population (tigecycline group,n= 261; combination group,n= 259), and 436 were clinically evaluable (tigecycline group,n= 223; combination group,n= 213). The clinical responses in the tigecycline and the combination vancomycin and aztreonam groups were similar in the c-mITT population (84.3% versus 86.9%; difference, −2.6% [95% confidence interval, −9.0, 3.8];P= 0.4755) and the CE population (89.7% versus 94.4%; difference, −4.7% [95% confidence interval, −10.2, 0.8];P= 0.1015). Microbiologic eradication (documented or presumed) occurred in 84.8% of the patients receiving tigecycline and 93.2% of the patients receiving vancomycin and aztreonam (difference, −8.5 [95% confidence interval, −16.0, −1.0];P= 0.0243). The numbers of patients reporting adverse events were similar in the two groups, with increased nausea and vomiting rates in the tigecycline group and an increased incidence of rash and increases in alanine aminotransferase and aspartate aminotransferase levels in the combination vancomycin and aztreonam group. Tigecycline was shown to be safe and effective for the treatment of complicated skin and skin structure infections.

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. 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. 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. 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%). 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.