Tofacitinib is an oral Janus kinase (JAK) inhibitor that has been marketed and approved in the USA for the clinical treatment of rheumatoid arthritis, psoriasis and other inflammatory and autoimmune diseases. A phase I clinical trial was conducted to compare the bioequivalence and safety of tofacitinib (Chia Tai Tianqing Pharmaceutical Group Co., Ltd.) and Xeljanz® (Pfizer Inc.) in healthy Chinese subjects, providing basis for the clinical application of tofacitinib.
Healthy Chinese subjects (N = 32) were randomly assigned to two groups at a 1:1 ratio. Subjects orally took 5 mg tofacitinib or Xeljanz® per cycle in random sequence. Blood samples were collected at 15 sampling points per cycle, and plasma drug concentrations of tofacitinib or Xeljanz® were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and statistical analysis for the pharmacokinetic (PK) parameters. Subjects’ physical indicators were monitored during the whole process to evaluate drug safety.
The adjusted geometric mean ratios (GMRs) of the peak concentration (C), area under the curve (AUC) from time zero to the last measurable concentration (AUC) and AUC from time zero to observed infinity (AUC) were all within the range of 80-125%. The other PK parameter values were similar. The above values were all meeting the bioequivalence criteria with well safety.
The pharmacokinetic parameters and safety profile of tofacitinib were similar to those of Xeljanz® in healthy Chinese subjects. Therefore, tofacitinib can be considered bioequivalent to Xeljanz®, and the findings of this trial will promote the clinical application of tofacitinib.

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