Background/Purpose: Biosimilars offer comparable efficacy and safety to their originators, thereby improving patient access to affordable treatments. FK-Tocilizumab (FK-toci) is the first tocilizumab biosimilar approved by both FDA and EMA for the treatment of autoimmune diseases including moderate-to-severe Rheumatoid Arthritis (RA). Therapeutic equivalence of FK-toci to reference tocilizumab was shown in subjects with moderate to severe RA in APTURA-1, a randomized, double blind efficacy study. Since its launch in 2024, FK-toci has accumulated ~50,000 patient-treatment-years of exposure with no new safety information affecting its benefit-risk balance. This analysis assessed the efficacy of FK-toci in patient subgroups with and without prior biologic use to support a broader patient access, including for patients with more refractory disease histories.

Methods: Subjects (M/F) over ­18 years with moderate to severe RA were randomized to subcutaneous (SC) injections of 162 mg FK-toci or reference tocilizumab (originator) for 24 weeks (W). Randomization was stratified by previous exposure to biological treatment for RA (yes/no). A cohort of patients were switched from the originator to FK-toci at W24. The primary objective was to demonstrate therapeutic equivalence, with 90% and 95% CIs for the difference in DAS28-ESR LS mean change from baseline at W24 falling within predefined equivalence intervals ([-0.6, 0.5] and [-0.6, 0.6], respectively). ACR20 response at W24 was an important secondary endpoint. Both endpoints were analyzed in the subgroups with and without previous exposure to biologic treatment for RA.

Results: 604 patients were randomized, 302 on FK-toci and 302 on originator; 54 (28 and 26, respectively) were previously exposed to biologic treatment for RA. Gender, race, ethnicity, age and disease characteristics were all well balanced at baseline. In total, 77.8% of patients with previous biologic exposure reached ACR20 at W24, versus 83.3% for subjects without previous biologic exposure, with similar ACR20 response rates in the two treatment groups (Figure 1). Similar reduction of DAS28-ESR at W24 were observed in both subgroups and in the two treatment groups (Figure 2).

Conclusion: Subgroup analyses by prior biologic exposure support the therapeutic equivalence of FK-tocilizumab and the originator, with no clinically meaningful differences in efficacy. These findings reinforce the reliability of FK-tocilizumab across a range of patient profiles, including those with previous biologic treatment, and underscore its potential to expand access to effective RA therapy.

Figure 1 – ACR20 Response at Week 24 by Previous Exposure to Biologic Treatment for Rheumatoid Arthritis (ITT Analysis Set)

Figure 2 – DAS28-ESR Change from Baseline at Week 24 by Previous Exposure to Biologic Treatment for Rheumatoid Arthritis (ITT Analysis Set)

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparable-efficacy-of-fk-tocilizumab-and-reference-tocilizumab-in-rheumatoid-arthritis-patients-with-and-without-prior-biologic-exposure/