Population pharmacokinetics of tofacitinib in patients with active ankylosing spondylitis.

Abstract

Objective: To characterize tofacitinib pharmacokinetics (PK) in patients with active ankylosing spondylitis (AS) and estimate the effects of covariates on variability of PK parameters.

Materials and methods: Pooled data from two studies in patients with AS who received tofacitinib were analyzed using nonlinear mixed-effects modeling. Tofacitinib PK was described by a one-compartment model parameterized in terms of apparent oral clearance (CL/F), apparent volume of distribution (V/F), and a first-order absorption rate constant (k_a). Covariates evaluated: baseline age, sex, race, creatinine clearance (BCCL), and C-reactive protein for CL/F; baseline age/body weight for V/F.

Results: Analysis included 279 patients. The point estimates for CL/F, V/F, and k_a were 27.1 L/hour, 126 L, and 3.07 hour^-1, respectively, in a reference patient. Excluding BCCL, point estimates of area under the concentration-time curve (AUC) over a dosing interval at steady-state and maximum steady-state tofacitinib concentration (C_max) change vs. the reference patient ranged from 98 - 112% and 89 - 115%, respectively. Estimated AUC was 24% higher in a patient with BCCL = 50 mL/min vs. the reference patient (BCCL = 126 mL/min). Point estimates and 90% confidence intervals of the AUC and C_max ratios indicated no major differences in tofacitinib exposure over the range of baseline age/body weight studied, and sex/race.

Conclusion: Tofacitinib does not require dose adjustment/restriction for age, body weight, sex, or race based on the differences (< 20%) in exposure relative to a reference patient with AS. The tofacitinib CL/F and BCCL relationship was consistent with known contribution of renal excretion to total tofacitinib clearance.