Pharmacokinetics and bioequivalence of tofacitinib 5 mg in healthy Korean male subjects

Objective: Tofacitinib is an oral Janus kinase (JAK) inhibitor marketed as an immunomodulator that can effectively treat rheumatoid arthritis. This study aimed to compare the pharmacokinetics and evaluate the bioequivalence of tofacitinib free base (CKD-374) with those of tofacitinib citrate (Xeljanz). Materials and methods: A randomized, open-label, single-dose, 2-sequence, 2-period crossover study was conducted in healthy Korean male subjects. A total of 36 subjects were randomized into two sequence groups. At each period, subjects were administered the test formulation (tofacitinib free base, 5 mg) or the reference formulation (tofacitinib citrate, 8.078 mg; as tofacitinib, 5 mg). The plasma samples were collected up to 12 hours post dose and analyzed by liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters, including maximum plasma concentration (C-max) and area under the plasma concentration vs. time curve from dosing to the last measurable concentration (AUC(0-t)), were determined by non-compartmental analysis. The 90% confidence intervals (CIs) of the geometric mean ratios for C-max and AUC(0-t) were calculated to evaluate pharmacokinetic equivalence. Results: The 90% CIs of the geometric mean ratios of C-max and AUC(0-t) for tofacitinib free base to tofacitinib citrate were 0.9144 - 1.1230 and 1.0245 - 1.0932, respectively. All reported adverse events were of mild intensity, and there were no serious adverse events. Conclusion: In healthy Korean male adult subjects, the pharmacokinetic parameters of tofacitinib free base and tofacitinib citrate were evaluated and met the pharmacokinetic bioequivalent criteria. Both formulations were safe and well-tolerated.