The primary endpoint of this study was the comparison of reference adalimumab (ADA) and the biosimilar SB5 in terms of ACR20 response rates at 24 weeks. The results of the primary analysis, which have already been published, showed response rates were similar for both groups (72.4% for SB5 and 72.2% for ADA).
An important clinical consideration for the use of biosimilars is whether switching from reference product might result in loss of efficacy or increased immunogenicity or other safety concerns. The purpose of the current study therefore, which continued up to 52 weeks, was to evaluate the safety, immunogenicity, and efficacy of continuing SB5 treatment versus switching from ADA to SB5 (which may occur in clinical practice) versus continuing ADA treatment. Re-randomisation of the ADA group to transition to SB5 (ADA/SB5 group; n=125]) or to continue ADA (ADA/ADA group; n=129) occurred at 24 weeks.
The ACR20 response rates at week 52 were 73.4% in the ADA/ADA group and 78.8% in the switch group (ADA/SB5), suggesting response rates were not affected by switching. Analysis of other clinical endpoints also showed comparable trends, and safety was comparable across all treatment groups.
The incidence of overall antidrug antibodies was comparable across treatment groups after transition at week 24 (15.7% in the SB5/SB5 group, 16.8% in the ADA/SB5 group, and 18.3% in the ADA/ADA group). Emergent antidrug antibodies occurred in 9 of 160 patients (5.6%) in the SB5/SB5 group, 5 of 80 patients (6.3%) in the ADA/SB5 group, and 11 of 87 patients (12.6%) in the ADA/ADA group.
This transition study was not designed for statistical comparisons of equivalence; however, the results provide valuable data on switching from a reference product to a biosimilar.
Imraldi (SB5) has been licensed in the UK but has not yet been launched. A RMOC briefing paper on adalimumab is available, providing advice to commissioners and providers related to next steps with best-value adalimumab uptake, and planning associated with the patent expiry of the originator product (Humira) in October 2018.