SB4 is a biosimilar of reference etanercept (ETN). The long-term efficacy, safety, and immunogenicity of continuing SB4 vs switching from ETN to SB4 was evaluated in an open-label extension period of a phase 3, randomized, double-blind, multicenter study, published in Annals of the Rheumatic Diseases.

A total of 245 patients with rheumatoid arthritis (RA) were enrolled in the extension period of the study. Of these patients, 126 continued treatment with SB4 (SB4/SB4 group) and 119 switched from ETN to SB4 (ETN/SB4 group). American College of Rheumatology (ACR) response rates were comparable and sustained between the 2 groups, with ACR20 (ie, ≥20% improvement) response rates at week 100 of 77.9% in the SB4/SB4 arm vs 79.1% in the ETN/SB4 arm. Radiographic progression was comparable between the 2 groups.

Rates of treatment-emergent adverse events (TEAEs), reported after week 52, were 47.6% in the SB4/SB4 group vs 48.7% in the ETN/SB4 group. One patient in each treatment group developed a serious infection. There were no cases of active tuberculosis or injection-site reactions reported in any of the patients. In the SB4/SB4 arm, 1 patient died of hepatic cancer, which was considered to be related to the study drug. One patient in each of the treatment groups developed non-neutralizing antidrug antibodies.

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The investigators concluded that, in patients with RA, SB4 is effective and well tolerated over 2 years. Switching from ETN to SB4 was not associated with a loss of efficacy, a rise in TEAEs, or an increase in immunogenicity. Postmarketing surveillance and registry studies to monitor the efficacy and safety of SB4 for a variety of indications are ongoing.

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Emery P, Vencovský J, Sylwestrzak A, et al. Long-term efficacy and safety in patients with rheumatoid arthritis continuing on SB4 or switching from reference etanercept to SB4.  [published online August 9, 2017]. Ann Rheum Dis. doi: 10.1136/annrheumdis-2017-211591.