Multicenter, Double-Blind, Randomized, Phase II Trial To Assess the Safety and Efficacy of Ceftolozane-Tazobactam plus Metronidazole Compared with Meropenem in Adult Patients with Complicated Intra-Abdominal Infections

Ceftolozane-tazobactam (TOL-TAZ) is a novel antibacterial with activity against Pseudomonas aeruginosa and other common Gram-negative pathogens, including extended-spectrum beta -lactamase (ESBL)-producing Enterobacteriaceae, that are associated with complicated intra-abdominal infections (cIAIs). This prospective, double-blind, randomized, multicenter, phase II trial assessed patient clinical and microbiological responses to and the safety of TOL-TAZ plus metronidazole compared with those of meropenem. Hospitalized adults with cIAIs that required surgical intervention were randomized (2: 1) to receive intravenous (i.v.) TOL-TAZ (1.5 g [containing 1,000 mg TOL and 500 mg TAZ] every 8 h [q8h]) with or without i.v. metronidazole (500 mg q8h) or i.v. meropenem (1 g q8h) for 4 to 7 days. The primary endpoint was the clinical response at the test-of-cure visit in the microbiologically modified intent-to-treat (mMITT) and microbiologically evaluable (ME) populations. Secondary measures included the patients' microbiological response and safety. In total, 82 patients received TOL-TAZ (90.2% with metronidazole), and 39 received meropenem. For the mMITT population, clinical cure was seen in 83.6% of the patients (51/61; 95% confidence interval [CI], 71.9 to 91.8) who received TOL-TAZ and 96.0% of the patients (24/25; 95% CI, 79.6 to 99.9) who received meropenem (difference, -12.4%; 95% CI, -34.9% to 11.1%); in the ME population, clinical cure was seen in 88.7% and 95.8% of the patients (difference, -7.1%; 95% CI, -30.7% to 16.9%) who received TOL-TAZ and meropenem, respectively. TOL-TAZ demonstrated microbiological success against Escherichia coli (89.5%), Klebsiella pneumoniae (100%), and P. aeruginosa (100%). The adverse event rates were similar in the groups (50.0% with TOL-TAZ and 48.8% with meropenem). TOL-TAZ in combination with metronidazole was well tolerated and resulted in clinical and microbiological success rates supportive of further clinical development in patients with cIAIs.