Effect of co-administration of ketoconazole, a strong CYP3A inhibitor, on the pharmacokinetics, safety and tolerability of navitoclax, a first-in-class oral Bcl-2 family inhibitor, in cancer patients.

BACKGROUND AND AIM: Navitoclax is a targeted B-cell lymphoma-2 (Bcl-2) family protein inhibitor. The present study evaluated the effect of ketoconazole, a strong cytochrome P450 (CYP) 3A4 inhibitor, on the pharmacokinetics of navitoclax in patients with cancer. PATIENTS AND METHODS: Eleven patients with cancer were enrolled in this Phase I study. Single doses of navitoclax at 60 mg were administered orally on days 1 and 8. Ketoconazole at 400 mg was given once daily from days 7 through 10. Blood samples were collected pre-dose through 72 h after each navitoclax dose.
RESULTS: Ten patients had evaluable pharmacokinetic data and were, therefore, included in pharmacokinetic statistical analyses. The maximum observed plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC) from time 0 to infinite time (AUC∞) of navitoclax in the presence of ketoconazole was 94% (90% confidence interval (CI)=53165%) and 155% (90% CI=91264%), respectively of those observed with navitoclax when administered alone. The increase in navitoclax AUC∞ was primarily driven by two patients, who had 5-fold and 11-fold increases, respectively, in navitoclax AUC∞ in the presence of ketoconazole. These two participants had unusually low plasma drug exposure when navitoclax was administered alone, and their navitoclax exposure in the presence of ketoconazole increased to be within the range of the other 8 patients. There were no adverse events related to navitoclax exposure reported in these 2 patients.
CONCLUSION: Co-administration of navitoclax with ketoconazole did not increase navitoclax exposure above that observed with navitoclax monotherapy and did not appear to affect its safety profile. Results suggest CYP3A does not play a major role in elimination of navitoclax.