Pharmacokinetics, Safety, and Clinical Outcomes of Omadacycline in Women with Cystitis: Results from a Phase 1b Study

Omadacycline, an aminomethylcycline antibiotic, is approved as once-daily intravenous (i.v.) and oral (p.o.) monotherapy for acute bacterial skin and skin structure infections and for community-acquired bacterial pneumonia, and it is under development for treatment of urinary tract infection (UTI). This is a phase 1b, randomized, open-label study of omadacycline in women with cystitis (defined as UTI symptoms and a positive urine leukocyte esterase test). Patients received omadacycline for 5 days (group 1: 200 mg intravenously on day 1, then 300 mg orally every 24 h [q24h]; group 2: 300 mg orally every 12 h [q12h] on day 1, then 300 mg orally q24h; group 3: 450 mg orally q12h on day 1, then 450 mg orally q24h). Blood and urine samples were collected over 5 days. Investigator-assessed clinical response was determined at end of treatment (EOT; day 6) and posttreatment evaluation (PTE; 5 to 9 days after last dosing). A total of 31 women were treated. At steady state (day 5), the range of mean omadacycline urine concentrations over 24 h across the groups was 17.94 to 48.12 μg/ml. The most common treatment-emergent adverse events were gastrointestinal (including nausea [60% to 73%] and vomiting [20% to 40%]) and were generally mild and transient. Investigator-determined clinical success was observed in 94% and 84% of patients at EOT and PTE, respectively, with similar results across groups. A favorable microbiological response at PTE was observed in 78% of patients who had a baseline pathogen. Omadacycline is partially excreted in urine and appears to be safe and well tolerated. These preliminary results indicate that omadacycline warrants further evaluation in larger controlled UTI studies.