Non-medical switching from tocilizumab to sarilumab in rheumatoid arthritis patients with low disease activity, an observational study.

Tocilizumab and sarilumab are IL6-receptor antagonists registered for rheumatoid arthritis, with equal effectiveness and safety. Switching from tocilizumab to sarilumab could be a strategy to reduce injection burden, in case of drug shortages, and to reduce costs. This study therefore aims to investigate the effectiveness and safety of switching RA patients with well-controlled disease under tocilizumab treatment to sarilumab. RA patients with low disease activity (DAS28-CRP<2.9 or <3.5 with clinical judgement), on stable dose tocilizumab (>6 months) were offered to switch to sarilumab. Patients who switched and consented were followed for 6 months. Sarilumab was started at 200mg and double the last tocilizumab interval. Co-primary outcomes at 6 months were 1) the 90% confidence interval (CI) of DAS28-CRP change from baseline compared to the non-inferiority margin of 0.6 and 2) the 90% CI of the proportion of patients persisting with sarilumab, compared to a pre-specified minimum of 70%. Of 50 invited patients, 25 agreed to switch to sarilumab, and 23 patients switched and were included. One patient was lost to follow up immediately after inclusion, therefore 22 patients are included in analyses. At 6 months, mean change in DAS28-CRP was 0.48 (90%CI: 0.11 to 0.87), compared to the non-inferiority margin of 0.6. Sarilumab persistence was 68% (90%CI: 51% to 82%, 15 out of 22 patients), compared to the pre-specified minimum of 70%. Non-medical switching from tocilizumab to sarilumab in patients doing well on tocilizumab failed to show non-inferiority regarding disease activity and drug persistence.