Evaluation of the effects of bitopertin (RG1678) on cardiac repolarization: a thorough corrected QT study in healthy male volunteers

Background: Bitopertin (RG1678) is a selective glycine reuptake inhibitor currently in Phase III development for the treatment of schizophrenia. Thorough QT studies to assess the effects of candidate drugs on cardiac repolarization and proarrhythmic potential are required by regulatory authorities and are a common part of the drug development process. A clinically relevant effect on QT interval is suspected if prolongation of the corrected QT interval (QTc) is ∼5 milliseconds or more, evidenced by an upper 1-sided 95% CI for the mean effect on the QTc of at least 10 milliseconds.

Objective: The goal of this study was to investigate the effect of bitopertin on the QTc interval in healthy male volunteers.

Methods: This was a multiple-dose, randomized, double-blind, double-dummy, placebo-controlled, parallel-group study using bitopertin 30 mg (n = 56) or bitopertin 175 mg (n = 56) once daily for 10 days plus placebo on day 11, moxifloxacin 400 mg on day 1 plus placebo once daily for 10 days (n = 29), or placebo once daily for 10 days plus moxifloxacin 400 mg on day 11 (n = 28). Continuous Holter ECGs were obtained on days -1, 1, 10, and 11, and the placebo-corrected mean change from time-matched baseline in the QT interval calculated by using Fridericia's formula (QTcF) on day 10 was the primary end point. Pharmacokinetic parameters of bitopertin were determined on day 10 by using HPLC-MS/MS methods to obtain bitopertin plasma drug concentrations. Adverse events were recorded throughout the study.

Results: A total of 169 predominantly white, healthy male volunteers (mean age, 31.8 years; range, 19-59 years) were randomized to treatment; 162 completed the study. The mean change in placebo-corrected QTcF from baseline to day 10 of bitopertin ranged from -2.8 to 3.9 milliseconds. The upper bound of the 1-sided 95% CI was <10 milliseconds at all time points with both doses. There was no relation between bitopertin concentrations and changes in QTcF or other ECG variables. Assay sensitivity was confirmed by a placebo-corrected mean change from time-matched baseline in QTcF of 10.6 milliseconds (lower bound of the 1-sided 98.3% CI, 6.9 milliseconds) 4 hours after moxifloxacin administration. Peak bitopertin plasma concentrations were achieved ∼4 hours after dosing. The terminal elimination t(½) was ∼53 hours. No safety or tolerability concerns were noted with bitopertin at either dose. Dizziness, nausea, and blurred vision were more common in the bitopertin 175-mg group compared with the bitopertin 30-mg or placebo groups.

Conclusion: Multiple dosing with bitopertin 30 mg or 175 mg did not affect QTcF in these healthy male volunteers. ClinicalTrials.gov identifier: NCT01613040.