Open-Label Assessment of the Effects of Itraconazole and Rifampicin on Balovaptan Pharmacokinetics in Healthy Volunteers

Introduction: Balovaptan, an investigational vasopressin 1a receptor antagonist that has been evaluated for improvement of social communication and interaction, is primarily metabolized by cytochrome P450 3A4 (CYP3A4).

Methods: Two single-center, non-randomized, two-period, phase 1 studies assessed the effect of the strong CYP3A4 inhibitor itraconazole (study NCT03579719) or the strong CYP3A4 inducer rifampicin (study NCT03586726) at steady state on the pharmacokinetics (PK) of steady-state balovaptan in healthy volunteers. Participants received balovaptan (5 or 10 mg/day) alone for 10 days, or in combination with itraconazole (200 mg/day) for 15 days, or rifampicin (600 mg/day) for 10 days, following balovaptan washout and itraconazole/rifampicin pre-dosing. Geometric mean ratios (GMRs) and 90% confidence intervals (90% CIs) for the area under the concentration-time curve over the dosing interval (AUC) and maximum plasma concentration (C_max) of balovaptan dosed with vs. without itraconazole/rifampicin were estimated from a mixed effects model.

Results: Both studies comprised 15-16 healthy male and female volunteers. Itraconazole 200 mg/day elevated steady-state exposure to 5 mg/day balovaptan approximately 4.5-5.5-fold (Day 15 GMR [90% CI], 4.46 [4.06-4.90] for C_max and 5.57 [5.00-6.21] for AUC) and extended the time to steady state from ~ 5 days to ~ 13-14 days. Rifampicin 600 mg/day resulted in ~ 90% reductions in both the C_max (Day 10 GMR [90% CI], 0.14 [0.12-0.15]) and AUC (0.07 [0.06-0.07]) of balovaptan 10 mg/day. Time to balovaptan steady state could not be determined with rifampicin. There were no clinically significant safety findings in either study.

Conclusions: Strong modulators of CYP3A4 activity will significantly alter the PK of balovaptan, with the effect of CYP3A4 induction greater than that of inhibition. Caution should be taken when concomitantly dosing balovaptan with moderate or strong CYP3A4 inducers or strong CYP3A4 inhibitors.

Trial registration number: NCT03579719; NCT03586726.