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.