Lack of Effect of Aprepitant or Its Prodrug Fosaprepitant on QTc Intervals in Healthy Subjects

BACKGROUND: A single 115-mg dose of fosaprepitant, the IV prodrug of the NK(1) receptor antagonist aprepitant, is bioequivalent to a 125-mg dose of oral aprepitant. Thus far, fosaprepitant/aprepitant has not shown a meaningful effect on QTc intervals; in this study, we sought to confirm these findings. METHODS: This double-blind, active-controlled, randomized, three-treatment, three-period, crossover study in healthy young subjects evaluated the effect of a 200-mg dose of fosaprepitant on QTc prolongation. In each period, subjects received 400 mg moxifloxacin per os, 200 mg fosaprepitant IV, or placebo in randomized sequence. The effect of fosaprepitant on QTc interval was assessed by 12-lead electrocardiograms (ECGs). The baseline value for QTc interval for each subject during each period was defined as the average of five replicate baseline QTc intervals extracted from predose ECGs. ECGs were performed at predose, 2, 5, 10, 15, 20, 30, 45 min; and 1, 1.5, 2, 3, 4, 6, and 8 h postinfusion. Values for individual QTc change from baseline were evaluated in a repeated-measures mixed model appropriate for a crossover design. A two-sided 90% confidence interval (CI) for the true difference in QTc interval change from baseline at each timepoint was calculated for fosaprepitant versus placebo and for moxifloxacin versus placebo. RESULTS: After fosaprepitant 200-mg administration, the mean (95% CI) QTc interval change from baseline at T(max) was -1.45 (-4.67 to 1.77) ms, and the placebo-corrected mean (90% CI) QTc interval change from baseline was -1.37 (-4.78 to 2.05) ms. Neither was statistically significant at alpha = 0.05. After 400 mg moxifloxacin administration, the mean (95% CI) QTc interval change from baseline at 2 h was 9.71 (6.49-12.93) ms, and the placebo-corrected mean (90% CI) QTc interval change from baseline at moxifloxacin T(max) was 10.50 (7.09-13.92) ms. Both were statistically significant at alpha = 0.05. The maximum aprepitant concentration after fosaprepitant 200 mg administration was 6300 ng/mL (approximately twofold, fourfold, and ninefold higher than that observed historically with fosaprepitant 115 mg [3095 ng/mL], aprepitant 125 mg [1600 ng/mL], and aprepitant 40 mg [675 ng/mL]). CONCLUSIONS: In subjects receiving fosaprepitant 200 mg, no clinically meaningful increases in QTc were seen at any timepoint, whereas after moxifloxacin 400 mg, increases were observed at the approximate T(max) of moxifloxacin and additional timepoints. The lack of QTc increase at this high dose of fosaprepitant and resulting aprepitant plasma exposures support the expectation that clinical doses of fosaprepitant or aprepitant will not be associated with significant QTc prolongation.