, 5.6 ± 7.0 mcg/mL, and 12.3 ± 8.7 mcg/mL, respectively. The accumulation ratios for AUC, Cmin, and Cmax were 2.67, 5.6, and 2.12, respectively. Steady state was reached after 12 weeks for AUC and Cmin, and after 10 weeks for Cmax.
Polyarticular Juvenile Idiopathic Arthritis—Intravenous Administration
The pharmacokinetics of tocilizumab was determined using a population pharmacokinetic analysis on a database composed of 188 patients with polyarticular juvenile idiopathic arthritis.
For doses of 8 mg/kg tocilizumab (patients with a body weight at or above 30 kg) given every 4 weeks, the estimated mean (± SD) AUC4weeks, Cmax and Cmin of tocilizumab were 29500 ± 8660 mcg∙hr/mL, 182 ± 37 mcg/mL and 7.49 ± 8.2 mcg/mL, respectively.
For doses of 10 mg/kg tocilizumab (patients with a body weight less than 30 kg) given every 4 weeks, the estimated mean (± SD) AUC4weeks, Cmax and Cmin of tocilizumab were 23200 ± 6100 mcg∙hr/mL, 175 ± 32 mcg/mL and 2.35 ± 3.59 mcg/mL, respectively.
The accumulation ratios were 1.05 and 1.16 for AUC4weeks, and 1.43 and 2.22 for Cmin for 10 mg/kg (BW less than 30 kg) and 8 mg/kg (BW at or above 30 kg) doses, respectively. No accumulation for Cmax was observed.
Systemic Juvenile Idiopathic Arthritis—Intravenous Administration
The pharmacokinetics of tocilizumab were determined using a population pharmacokinetic analysis on a database composed of 75 patients with SJIA treated with 8 mg per kg (patients with a body weight at or above 30 kg) or 12 mg per kg (patients with a body weight less than 30 kg), given every 2 weeks. The estimated mean (± SD) AUC2 weeks, Cmax and Cmin of tocilizumab were 32200 ± 9960 mcg∙hr per mL, 245 ± 57.2 mcg per mL and 57.5 ± 23.3 mcg per mL, respectively. The accumulation ratio for Cmin (week 12 over week 2) was 3.2 ± 1.3. Steady state was reached on or after week 12. Mean estimated tocilizumab exposure parameters were similar between the two dose groups defined by body weight.
Absorption
Following SC dosing in rheumatoid arthritis patients, the absorption half-life was around 4 days. The bioavailability for the SC formulation was 0.8.
Distribution
Following intravenous dosing, tocilizumab undergoes biphasic elimination from the circulation. In rheumatoid arthritis patients the central volume of distribution was 3.5 L and the peripheral volume of distribution was 2.9 L, resulting in a volume of distribution at steady state of 6.4 L.
In pediatric patients with PJIA, the central volume of distribution was 1.98 L, the peripheral volume of distribution was 2.1 L, resulting in a volume of distribution at steady state of 4.08 L.
In pediatric patients with SJIA, the central volume of distribution was 0.94 L, the peripheral volume of distribution was 1.60 L resulting in a volume of distribution at steady state of 2.54 L.
Elimination
The total clearance of tocilizumab is concentration-dependent and is the sum of the linear clearance and the nonlinear clearance. The linear clearance in the population pharmacokinetic analysis was estimated to be 12.5 mL per h in RA, 5.8 mL per h in pediatric patients with PJIA, and 7.1 mL per h in pediatric patients with SJIA. The concentration-dependent nonlinear clearance plays a major role at low tocilizumab concentrations. Once the nonlinear clearance pathway is saturated, at higher tocilizumab concentrations, clearance is mainly det |
