Evaluation of the effect of ritlecitinib on the pharmacokinetics of caffeine in healthy participants

Aims This clinical study was conducted to evaluate the impact of ritlecitinib on the pharmacokinetics of caffeine, a cytochrome P450 1A2 (CYP1A2) substrate. Methods In this single‐centre, single‐arm, open‐label, fixed‐sequence study, healthy participants received a single 100‐mg dose of caffeine on 2 separate occasions: on Day 1 of Period 1 as monotherapy and on Day 8 of Period 2 after oral administration of ritlecitinib 200 mg once daily for 8 days. Serial blood samples were collected and analysed using a validated liquid chromatography–mass spectrometry assay. Pharmacokinetic parameters were estimated by using a noncompartmental method. Safety was monitored by physical examination, vital signs, electrocardiograms and laboratory assessments. Results Twelve participants were enrolled and completed the study. Coadministration of caffeine 100 mg in the presence of steady‐state levels of ritlecitinib (200 mg once daily) increased caffeine exposure compared with caffeine given alone. Area under the curve to infinity and maximum concentration of caffeine increased by approximately 165 and 10%, respectively, when coadministered with ritlecitinib. The ratios of the adjusted geometric means (90% confidence interval) for caffeine area under the curve to infinity and maximum concentration were 265.14% (234.12–300.26%) and 109.74% (103.90–15.91%), respectively, when caffeine was coadministered with steady‐state ritlecitinib (test) compared with its administration alone (reference). Multiple doses of ritlecitinib when coadministered with a single dose of caffeine were generally safe and well tolerated in healthy participants. Conclusion Ritlecitinib is a moderate inhibitor of CYP1A2 and can increase systemic exposures of CYP1A2 substrates.