Comparison of the Pharmacokinetics of Subcutaneous Ustekinumab between Chinese and Non-Chinese Healthy Male Subjects across Two Phase 1 Studies

Ustekinumab, a human immunoglobulin G1 kappa (IgG1κ) monoclonal antibody against interleukin-12/23p40, has been reported to be significantly efficacious in treating patients with moderate-to-severe plaque psoriasis. Although the efficacy and safety of ustekinumab have been previously studied in Asian patients with psoriasis, the pharmacokinetics of ustekinumab has not been reported for Asian patients. The objective of this analysis was to compare the pharmacokinetics of ustekinumab in Chinese and non-Chinese subjects.

Two Phase 1, open-label, single-period, inpatient/outpatient studies were conducted to evaluate the pharmacokinetics of ustekinumab following a single subcutaneous (SC) injection. In Study 1, non-Chinese healthy male subjects (n = 31) received a single SC injection of ustekinumab 90 mg. In Study 2, Chinese healthy male subjects (n = 24) were randomized (1:1) to receive a single SC injection of ustekinumab 45 mg or 90 mg. Serum ustekinumab concentrations were measured using validated immunoassays. The pharmacokinetic parameters were calculated using non-compartmental analyses. After data collection, a linear mixed model approach was used to compare the log-transformed maximum observed serum concentration (C_max) and area under the serum concentration–time curves (AUCs) generated from the 90-mg dose groups in the two studies. The ratios of the geometric means of the C_max and AUCs in Chinese subjects (Test) to those in non-Chinese subjects (Reference) along with the 90 % confidence intervals (CIs) were calculated.

The mean body weight was 80.3 kg in non-Chinese (Caucasian: 77.4 %; black: 12.9 %; Asian: 0.0 %; other: 9.7 %) and 65.7 kg in Chinese subjects, with an overall mean of 74 kg. Across studies and dose groups, the median time corresponding to the C_max (t_max) was 4.0–8.5 days, the mean terminal half-life (t_½) was approximately 3 weeks, and the mean apparent volume of distribution based on the terminal phase (V_z/F) was 80.3–97.3 mL/kg. In the 90-mg groups, mean exposure parameters of ustekinumab were 1.1- to 1.3-fold higher in Chinese versus non-Chinese subjects. However, exposure parameters were not significantly different between the two study populations when individual parameters were adjusted to a subject weighing 74 kg: the 90 % CIs of the geometric mean ratios (Chinese versus non-Chinese) for weight-adjusted C_max, AUC from time zero to time of last measurable concentration (AUC_last), and AUC from time zero to infinity (AUC_∞) were (0.76–1.09), (0.85–1.16) and (0.88–1.22), respectively. Ustekinumab was generally well tolerated, with no unexpected adverse events; one subject (non-Chinese) developed anti-drug antibodies to ustekinumab.

The pharmacokinetics of ustekinumab were comparable between Chinese and non-Chinese healthy male subjects when exposure parameters were adjusted by subject body weight.

Study 1, conducted with non-Chinese subjects (March–July 2006), was completed before the 7th revision of the Declaration of Helsinki and was therefore exempt from registration under the existing guidelines. The clinical trial registration number for Study 2, conducted with Chinese subjects (October 2009–June 2010), is NCT01081704.