Ceftolozane/Tazobactam Plus Metronidazole for Complicated Intra-abdominal Infections in an Era of Multidrug Resistance: Results From a Randomized, Double-Blind, Phase 3 Trial (ASPECT-cIAI)

Abstract

Background: Increasing antimicrobial resistance among pathogens causing complicated intra-abdominal infections (cIAIs) supports the development of new antimicrobials. Ceftolozane/tazobactam, a novel antimicrobial therapy, is active against multidrug-resistant Pseudomonas aeruginosa and most extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae.

Methods: ASPECT-cIAI (Assessment of the Safety Profile and Efficacy of Ceftolozane/Tazobactam in Complicated Intra-abdominal Infections) was a prospective, randomized, double-blind trial. Hospitalized patients with cIAI received either ceftolozane/tazobactam (1.5 g) plus metronidazole (500 mg) every 8 hours or meropenem (1 g) every 8 hours intravenously for 4-14 days. The prospectively defined objectives were to demonstrate statistical noninferiority in clinical cure rates at the test-of-cure visit (24-32 days from start of therapy) in the microbiological intent-to-treat (primary) and microbiologically evaluable (secondary) populations using a noninferiority margin of 10%. Microbiological outcomes and safety were also evaluated.

Results: Ceftolozane/tazobactam plus metronidazole was noninferior to meropenem in the primary (83.0% [323/389] vs 87.3% [364/417]; weighted difference, -4.2%; 95% confidence interval [CI], -8.91 to .54) and secondary (94.2% [259/275] vs 94.7% [304/321]; weighted difference, -1.0%; 95% CI, -4.52 to 2.59) endpoints, meeting the prespecified noninferiority margin. In patients with ESBL-producing Enterobacteriaceae, clinical cure rates were 95.8% (23/24) and 88.5% (23/26) in the ceftolozane/tazobactam plus metronidazole and meropenem groups, respectively, and 100% (13/13) and 72.7% (8/11) in patients with CTX-M-14/15 ESBLs. The frequency of adverse events (AEs) was similar in both treatment groups (44.0% vs 42.7%); the most common AEs in either group were nausea and diarrhea.

Conclusions: Treatment with ceftolozane/tazobactam plus metronidazole was noninferior to meropenem in adult patients with cIAI, including infections caused by multidrug-resistant pathogens.

Clinical trials registration: NCT01445665 and NCT01445678.

Keywords: Enterobacteriaceae; ceftolozane/tazobactam; complicated intra-abdominal infection; gram-negative bacteria; multidrug resistance.

Figure 1.

Patient disposition in ASPECT-cIAI (Assessment of the Safety Profile and Efficacy of Ceftolozane/Tazobactam in Complicated Intra-abdominal Infections). ^aPatients could be excluded for more than one reason. Abbreviations: BIP, baseline infecting pathogen; CE, clinically evaluable; MITT, microbiological ITT.

Figure 2.

Primary and secondary analysis endpoints at the test-of-cure visit. In the microbiological intent-to-treat (MITT) population, a treatment failure approach was used, where indeterminate clinical responses were imputed as failures. In the microbiologically evaluable (ME) population, a data-as-observed approach was used, where indeterminate clinical responses were excluded from the analysis. Abbreviations: CI, confidence interval; NI, noninferiority margin.