The phase III, randomized, double-blind, parallel-group study was conducted at 73 centres across 10 countries in Europe, Latin America and Asia. A total of 596 patients aged 18–75 years with moderate to severe RA despite methotrexate therapy were enrolled. Patients were randomly assigned (1:1) to receive a once weekly dose of 50 mg SB4 (N = 299) or Enbrel (N = 297) administered subcutaneously for 52 weeks. All patients also had to take methotrexate (10–25 mg/week) and folic acid (5–10 mg/week) during the study. The primary endpoint in the study was the American College of Rheumatology 20% response criteria (ACR20) at week 24.

The study is currently ongoing, however, Emery and co-authors presented efficacy data up to 24 weeks of treatment and safety data up to the 24-week interim report data cut-off point (21 July 2014).

The ACR20 response rate at Week 24 in the per-protocol set was 78.1% (193/247) in the SB4 group and 80.3% (188/234) in the Enbrel group. The rate difference adjusted by region and baseline C-reactive protein was −1.67% (95% confidence interval [95% CI], −10.13% to 6.78%), which was within the predefined equivalence margin of [−15%, 15%], indicating therapeutic equivalence between SB4 and Enbrel.

Other efficacy endpoints and pharmacokinetic endpoints were comparable. The incidence of treatment-emergent adverse events was comparable (55.2% vs 58.2%). The incidence of anti-drug antibody development up to week 24 was lower in the SB4 group compared with the Enbrel group [2 patients (0.7%) vs 39 patients (13.1%)]. The anti-drug antibodies appeared early (between weeks 2 and 8) and most of them disappeared after week 12.

K analyses were performed on 79 patients (41 SB4 and 38 ETN). C_trough were comparable at each time point between SB4 (ranging from 2.419 to 2.886 μg/mL in weeks 2–24) and Enbrel (ranging from 2.066 to 2.635 μg/mL in weeks 2–24). The AUC_τ at week 8 was 676.4 vs 520.9 μg h/mL and the inter-subject variability (CV%) was 37.7% vs 50.1% in SB4 and Enbrel, respectively.

The authors concluded that ‘SB4 was shown to be equivalent with ETN [Enbrel] in terms of efficacy at week 24. SB4 was well tolerated with a lower immunogenicity profile. The safety profile of SB4 was comparable with that of ETN.’

Conflict of interest
The authors of the research paper [1] have received grant/research support from Samsung Bioepis. Some of the authors have worked as consultants for Samsung Bioepis and other pharmaceutical companies. For full details of the authors’ conflicts of interest, see the research paper [1].

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Reference
1.  Emery P, et al. A phase III randomised, double-blind, parallel-group study comparing SB4 with etanercept reference product in patients with active rheumatoid arthritis despite methotrexate therapy. Ann Rheum Dis. 2015 Jul 6. pii: annrheumdis-2015-207588.

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