No abstract

This article describes studies that investigated the pharmacokinetics of nilotinib, a highly specific, oral, second-generation BCR-ABL tyrosine kinase inhibitor. After a once- or twice-daily regimen at doses ranging from 50 to 1,200 mg/day in 119 patients with chronic myeloid leukemia (CML), the area under the serum concentration-time curve (AUC) and peak serum concentration (C(max)) of nilotinib were found to be nearly dose proportional up to a dose of 400 mg once daily. Solubility-limited absorption at higher doses was observed, but this was partially overcome by dividing the daily dose into two. For instance, the administration of 400 mg nilotinib twice daily resulted in a 35% increase in AUC as compared to a once-daily dose of 800 mg. Exploratory pharmacodynamic assessment showed a general trend of greater reduction in white blood cell (WBC) levels with increase in nilotinib concentrations. This finding was consistent with the observation of an 82% reduction in WBC levels in patients after a regimen of 400 mg nilotinib twice daily for 15 days. The type and quantity of food intake variably affected nilotinib absorption. When administered after a high-fat meal, the AUC of nilotinib increased by 50% in CML patients (n = 10) and by 82% in healthy volunteers (n = 44).

Nilotinib (Tasigna), an orally bioavailable second-generation BCR-ABL tyrosine kinase inhibitor, is approved for use in patients with chronic myeloid leukemia in chronic phase and accelerated phase who are resistant or intolerant to prior therapy, including imatinib. Previous in vitro studies indicated that nilotinib metabolism is primarily mediated by CYP3A4. To investigate the effect of CYP3A4 induction and inhibition on nilotinib pharmacokinetics, 2 studies were conducted in healthy volunteers prior to and following treatment with a strong inducer (rifampin) or inhibitor (ketoconazole). In the induction study, administration of rifampin 600 mg once daily for 8 days significantly increased urinary 6β-hydroxycortisol/ cortisol ratio, from a preinduction baseline of 5.8 ± 2.7 to 18.0 ± 10.2 after 8 days of rifampin treatment, confirming an inductive effect on CYP3A4. Nilotinib oral clearance was increased by 4.8-fold, and the maximum serum concentration (C(max)) and area under the serum concentration-time curve (AUC) were decreased by 64% and 80%, respectively, in the induced state compared with baseline. In the inhibition study, ketoconazole 400 mg once daily for 6 days increased the C(max) and AUC of nilotinib by 1.8- and 3-fold, respectively, compared with nilotinib alone. These results indicate that concurrent use of strong CYP3A4 inducers or inhibitors may necessitate dosage adjustments of nilotinib and should be avoided when possible.