Effect of ketoconazole, a strong CYP3A inhibitor, on the pharmacokinetics of venetoclax, a BCL-2 inhibitor, in patients with non-Hodgkin lymphoma

Aims: To examine the effect of a strong cytochrome P450 (CYP) 3A inhibitor, ketoconazole, on the pharmacokinetics, safety and tolerability of venetoclax. Methods: Twelve patients with non-Hodgkin lymphoma (NHL) were enrolled in this Phase 1, open-label, fixed-sequence study. Patients received a single 50 mg dose of venetoclax orally on Day 1 and Day 8, and a 400 mg once daily dose of ketoconazole on Days 5–11. Blood samples were collected predose and up to 96 h after each venetoclax dose on Day 1 and Day 8. Results: Eleven patients had evaluable pharmacokinetic data and were therefore included in the statistical analyses. Compared to administration of a single 50 mg dose of venetoclax alone, ketoconazole increased the venetoclax mean maximum observed plasma concentration (C_max) and area under the plasma concentration–time curve from time 0 to infinity (AUC_∞) by 2.3-fold (90% confidence interval [CI]: 2.0–2.7) and 6.4-fold (90% CI: 4.5–9.2; range: 2- to 12-fold), respectively. Conclusions: Coadministration of venetoclax with multiple doses of ketoconazole resulted in a significant increase of venetoclax exposures, strongly suggesting that CYP3A plays a major role in elimination of venetoclax in patients. These results suggest the need to avoid concomitant use with strong and moderate inhibitors or inducers of CYP3A during the venetoclax ramp-up phase in chronic lymphocytic leukaemia (CLL) patients. For patients who have completed the ramp-up phase, a modification in venetoclax dose for use with strong and moderate inhibitors or inducers of CYP3A is recommended.