To evaluate the safety, efficacy, and pharmacokinetics of 50 mg etanercept administered subcutaneously once weekly in adult patients with active rheumatoid arthritis (RA).
Four hundred twenty RA patients were randomized to receive, in a blinded manner, the study drug for up to 16 weeks: 214 patients received 50 mg etanercept once weekly, 153 received 25 mg etanercept twice weekly, and 53 received placebo for 8 weeks followed by 25 mg etanercept twice weekly for 8 weeks. Efficacy and safety were assessed at weeks 8 and 16. Pharmacokinetic analyses were performed on serum samples from patients at selected study sites. The primary efficacy end point was achievement of the American College of Rheumatology (ACR) 20% improvement criteria (ACR20 response) at week 8.
An ACR20 response was achieved at week 8 by 50% of the patients receiving 50 mg etanercept once weekly, by 49% of the patients receiving 25 mg etanercept twice weekly, and by 19% of the patients in the placebo group (P </= 0.0001 for each etanercept group versus placebo). Similarly, achievement of the ACR50 response was attained by 18% of patients in each of the 2 etanercept groups, compared with 6% of patients in the placebo group (P < 0.03 for each comparison). Pharmacokinetics of the 2 etanercept regimens were similar at steady state. No clinically significant differences in efficacy or safety were observed between the 2 etanercept groups.
Safety, efficacy, and pharmacokinetics were comparable between the 2 etanercept dosing regimens. Thus, comparable clinical outcomes are to be expected when patients are treated with etanercept administered either as 50 mg once weekly or as 25 mg twice weekly.