The Effect of Multiple Oral Doses of a Glycine Transporter 1 Inhibitor, Iclepertin (BI 425809), on the Steady-state Pharmacokinetics of a Combined Oral Contraceptive Containing Ethinylestradiol and Levonorgestrel: a Phase I Clinical Trial in Healthy Females.

Background: Iclepertin is a selective inhibitor of glycine transporter 1 recently investigated as a novel treatment for cognitive impairment associated with schizophrenia. Iclepertin is a potential mild inducer of liver cytochrome P450 3A4, which metabolises ethinylestradiol and levonorgestrel, which are used in combined oral contraceptives (OCs).

Objectives: This trial investigated the potential drug interaction effect of steady-state iclepertin on the steady-state pharmacokinetics of combined OCs.

Methods: This phase I, non-randomised, open-label, two-period, fixed-sequence trial was conducted in healthy pre-menopausal female volunteers aged 18-35 years. In period 1, participants received a combined OC (ethinylestradiol 30 µg/levonorgestrel 150 µg once daily; reference treatment). In period 2, participants received a combined OC and iclepertin 10 mg once daily (test treatment). Primary pharmacokinetic endpoints of ethinylestradiol or levonorgestrel in plasma at steady state over a uniform dosing interval τ were area under the concentration-time curve (AUC) and maximum and minimum measured concentration (C and C); drug interaction potential was estimated by geometric mean ratios (test treatment/reference treatment) with two-sided 90% confidence intervals (CIs) using analysis of variance. Safety assessments included monitoring adverse events (AEs).

Results: In total, 19 participants entered the trial; 17 were treated (periods 1 and 2). Steady-state pharmacokinetics of ethinylestradiol and levonorgestrel were similar with and without iclepertin; geometric mean ratios for AUC, C, and C were slightly above 100%, and 90% CIs were within standard bioequivalence boundaries (80-125%). The number of on-treatment AEs was similar in period 1 (n = 13) and period 2 (n = 15); AEs were of mild-to-moderate severity.

Conclusion: Iclepertin 10 mg had no meaningful effect on the pharmacokinetics of ethinylestradiol and levonorgestrel, suggesting that these drugs can be administered concomitantly.

Trial Registration: ClinicalTrials.gov (NCT05613777; registered on 18 October 2023).