The Effect of Rifampin on the Pharmacokinetics and Safety of Lorlatinib: Results of a Phase One, Open-Label, Crossover Study in Healthy Participants.

INTRODUCTION: Lorlatinib is a third-generation tyrosine kinase inhibitor approved for the treatment of anaplastic lymphoma kinase (ALK)-positive metastatic non-small cell lung cancer; cytochrome P450 (CYP) 3A plays an important role in the metabolism of lorlatinib. METHODS: This phase 1, open-label, two-period, crossover study estimated the effect of oral rifampin (a strong CYP3A inducer) on the pharmacokinetics and safety of oral lorlatinib (NCT02804399). Healthy participants received single-dose lorlatinib 100 mg in period 1 followed by rifampin 600 mg/day (days 1-12) and single-dose lorlatinib 100 mg (day 8) in period 2. Blood samples were collected for 120 h after each dose of lorlatinib. RESULTS: When a single dose of lorlatinib was administered during daily dosing with rifampin (period 2), the area under the plasma concentration-time profile extrapolated to infinity (AUCinf) and maximum plasma concentration (Cmax) of lorlatinib were 14.74% [90% confidence interval (CI) 12.78%, 17.01%] and 23.88% (90% CI 21.58%, 26.43%), respectively, of those in period 1 (lorlatinib alone). A single dose of lorlatinib was well tolerated in period 1, but elevations in transaminase values were observed in all participants (grade 2-4 in 11 participants) within 1-3 days after a single dose of lorlatinib was administered with ongoing rifampin in period 2. Rifampin dosing was therefore halted. Transaminase levels subsequently returned to normal (median time to recovery: 15 days). No elevations in bilirubin were observed. CONCLUSIONS: The addition of a single dose of lorlatinib to daily dosing with rifampin significantly reduced lorlatinib plasma exposure relative to a single dose of lorlatinib administered alone and was associated with severe but self-limiting transaminase elevations in all healthy participants. These observations support the contraindication in the product label against concomitant use of lorlatinib with all strong CYP3A inducers. TRIAL REGISTRATION: ClinicalTrials.gov identifier, NCT02804399.