The Effect of CYP3A Induction and Inhibition on the Pharmacokinetics of Laquinimod, a Novel Neuroimmunomodulator.

Laquinimod, a neuroimmunomodulator, is extensively metabolized by cytochrome P450 (CYP) 3A4, and modulations of CYP3A4 activity may lead to alterations in the pharmacokinetics and/or clinical effects of laquinimod. To determine the drug-drug interaction potential of laquinimod with CYP3A inhibitors and inducers, interaction assessments were conducted in healthy volunteers using single-dose administration of laquinimod before and after multiple dosing of CYP3A inhibitors (ketoconazole, fluconazole, and cimetidine) or a CYP3A4 inducer (rifampin). For ketoconazole, subjects (n = 14) received laquinimod 0.6 mg following 1 day of ketoconazole (400 mg daily) pretreatment, a single concomitant dose, and 28 additional days. For fluconazole, subjects (n = 14) received laquinimod 0.6 mg after a single fluconazole dose of 400 mg followed by 200-mg daily fluconazole administration for 20 additional days. For cimetidine, subjects (n = 14) received laquinimod 0.6 mg following 1 day of cimetidine (800 mg twice daily) pretreatment, a single concomitant dose, and 21 additional days. For rifampin, subjects (n = 14) received laquinimod 0.6 mg following 9 days of rifampin (600 mg daily) pretreatment, a single concomitant dose, and 12 additional days. Coadministration of laquinimod with CYP3A inhibitors, ketoconazole, fluconazole, and cimetidine increased laquinimod area under the plasma concentration-time curve from time zero to infinity by approximately 3.1-, 2.5-, and 1.1-fold, respectively. Coadministration of laquinimod with rifampin decreased laquinimod area under the plasma concentration-time curve from time zero to infinity by 5-fold. These results indicate that coadministration of laquinimod with moderate to strong inhibitors of CYP3A or strong inducers of CYP3A may give rise to significant pharmacokinetic drug interactions.