Tofacitinib 5 mg · Tablets

Tofacitinib is a Janus kinase (JAK) inhibitor. JAKs are intracellular enzymes which transmit signals arising from cytokine or growth factor-receptor interactions on the cellular membrane to influence cellular processes of hematopoiesis and immune cell function. Within the signaling pathway, JAKs phosphorylate and activate Signal Transducers and Activators of Transcription (STATs) which modulate intracellular activity including gene expression. Tofacitinib modulates the signaling pathway at the point of JAKs, preventing the phosphorylation and activation of STATs. JAK enzymes transmit cytokine signaling through pairing of JAKs (e.g., JAK1/JAK3, JAK1/JAK2, JAK1/TyK2, JAK2/JAK2). Tofacitinib inhibited the in vitro activities of JAK1/JAK2, JAK1/JAK3, and JAK2/JAK2 combinations with IC50 of 406, 56, and 1377 nM, respectively. However, the relevance of specific JAK combinations to therapeutic effectiveness is not known.

Following oral administration of tofacitinib tablets, peak plasma concentrations were reached within 0.5 hour -1 hour, elimination half-life was about 3 hours and a dose-proportional increase in systemic exposure was observed in the therapeutic dosage range. Steady state concentrations were achieved in 24-48 hours with negligible accumulation after twice daily administration.

Abbreviations: AUC24 = area under the concentration time profile from time 0 to 24 hours; Cmax = maximum plasma concentration; Cmin = minimum plasma concentration; Tmax = time to Cmax; CV = Coefficient of variation.

a Values represent the geometric mean, except Tmax, for which is the median (range) is shown.

b Values beyond 12 hours were after the evening dose which was administered 12 hours after the morning dose of twice-daily tofacitinib tablets.

Tofacitinib tablets — The absolute oral bioavailability of tofacitinib tablets is 74%. Coadministration of tofacitinib tablets with a high-fat meal resulted in no changes in AUC while Cmax was reduced by 32%. In clinical trials, tofacitinib tablets were administered without regard to meals [see Dosage and Administration (2.2)].

Distribution — After intravenous administration, the volume of distribution was 87 L. The protein binding of tofacitinib is approximately 40%. Tofacitinib binds predominantly to albumin and does not appear to bind to α1-acid glycoprotein. Tofacitinib distributes equally between red blood cells and plasma.

Metabolism and Excretion — Clearance mechanisms for tofacitinib are approximately 70% hepatic metabolism and 30% renal excretion of the parent drug. The metabolism of tofacitinib is primarily mediated by CYP3A4 with minor contribution from CYP2C19. In a human radiolabeled study, more than 65% of the total circulating radioactivity was accounted for by unchanged tofacitinib, with the remaining 35% attributed to 8 metabolites, each accounting for less than 8% of total radioactivity. The pharmacologic activity of tofacitinib is attributed to the parent molecule.

Pharmacokinetics in Patients with RA, PsA, AS, and UC — Population pharmacokinetic (PK) analyses indicated that PK characteristics were similar between patients with RA, PsA, ankylosing spondylitis, and UC. The coefficient of variation (%) in AUC of tofacitinib were generally similar across different disease patients, ranging from 22% to 34% (Table 9).

Abbreviations: AUC0-24,ss=area under the plasma concentration-time curve over 24 hours at steady state; CV=coefficient of variation.

a Pharmacokinetic parameters estimated based on population pharmacokinetic analysis.

Specific Populations — Covariate evaluation as part of population PK analyses in adult patient populations indicated no clinically relevant change in tofacitinib exposure, after accounting for differences in renal function (i.e., creatinine clearance) between patients, based on age, weight, biological sex and race (Figure 1). An approximately linear relationship between body weight and volume of distribution was observed, resulting in higher peak (Cmax) and lower trough (Cmin) concentrations in lighter patients. However, this difference is not considered to be clinically relevant.

Covariate evaluation as part of population PK analyses in pediatric patients with pcJIA, including PsA, identified body weight significantly impacting tofacitinib exposure, which supports weight-based dosing in this population. There were no identified clinically significant differences in tofacitinib exposure with different age, biological sex, racial, or pcJIA or PsA disease severity groups. The effect of renal and hepatic impairment and other intrinsic factors on the PK of tofacitinib is shown in Figure 1.

In patients with end-stage renal disease maintained on hemodialysis, mean AUC was approximately 40% higher compared with historical healthy subject data, consistent with approximately 30% contribution of renal clearance to the total clearance of tofacitinib[see Dosage and Administration (2.3, 2.4, 2.5)and Use in Specific Populations (8.6)].