Bioequivalence of the pharmacokinetics between tofacitinib aspartate and tofacitinib citrate in healthy subjects

Tofacitinib is an oral disease-modifying anti-rheumatic drug to selectively inhibit Janus kinases. Tofacitinib is a representative small molecule inhibitor that is used to treat many diseases including rheumatoid arthritis and various autoimmune conditions. Unlike biological agents, tofacitinib has several advantages, including the ability to be administered orally and a short half-life. This study aimed to evaluate the bioequivalence of the pharmacokinetics (PK) between tofacitinib aspartate 7.13 mg (test formulation) and tofacitinib citrate 8.08 mg (reference formulation; Xeljanz®) in healthy subjects. A randomized, open-label, single-dose, 2-sequence, 2-period, 2-treatment crossover trial was conducted in 41 healthy volunteers. A total of 5 mg of tofacitinib as the test or the reference formulation was administered, and serial blood samples were collected up to 14 hours after dosing for PK analyses. The plasma concentration of tofacitinib was determined by ultra-performance liquid chromatography-tandem mass spectrometry. A non-compartmental analysis was used to estimate the PK parameters. A total of 35 subjects completed the study and the study drug was well-tolerated. The mean maximum concentration (C(max)) and area under the concentration-time curve from time zero to the time of the last quantifiable concentration (AUC(last)) for the test formulation were 52.67 ng/mL and 133.86 ng∙h/mL, respectively, and 50.61 ng/mL and 133.49 h∙ng/mL for the reference formulation, respectively. The geometric mean ratios (90% confidence intervals) of the C(max) and AUC(last) between the 2 formulations were 1.041 (0.944–1.148) and 1.003 (0.968–1.039), respectively. Tofacitinib aspartate exhibited bioequivalent PK profiles to those of the reference formulation. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT04278391