Randomized, Double-Blind, Placebo- and Positive-Controlled Crossover Study of the Effects of Omadacycline on QT/QTc Intervals in Healthy Subjects

Omadacycline, an aminomethylcycline, is an antibiotic that is approved in the United States for once-daily intravenous (i.v.) and oral use for treatment of adults with acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia. In this thorough QT study, the effects of a therapeutic (100 mg i.v.) dose and a supratherapeutic (300 mg i.v.) dose of omadacycline on the electrocardiogram were studied, with placebo and moxifloxacin as negative and positive controls. Omadacycline at these doses had no effect on the QTc interval. The largest mean placebo-corrected change-from-baseline QTcS (ΔQTcS) were 1.7 ms (90% confidence interval [CI], 0.06 to 3.30) and 2.6 ms (90% CI, 0.55 to 4.67), observed at 20 min and 2 h after the start of the infusion of 100 mg and 300 mg, respectively. Assay sensitivity was demonstrated with moxifloxacin, which caused clear prolongation of QTcS, with the largest mean placebo-corrected ΔQTcS of 9.8 ms at 1.5 and 2 h. With a linear exposure-response model, the estimated slope of the concentration-change-from-baseline QTcF (ΔQTcF) relationship was very shallow: 0.0007 ms per ng/ml (90% CI, 0.0000 to 0.0014). The possibility of an effect on placebo-corrected ΔQTcS exceeding 10 ms can be excluded at omadacycline concentrations in plasma of up to ∼8 μg/ml. Omadacycline had no effect on cardiac conduction (PR and QRS intervals) but caused an increase in heart rate of 16.8 beats per min at 35 min after the 100-mg dose and 21.6 beats per min at 50 min after the 300-mg dose.