Comparative effectiveness of subcutaneous sarilumab 200 mg biweekly, subcutaneous Tocilizumab 162 mg biweekly, and intravenous Tocilizumab 8 mg/kg every 4 weeks in patients with rheumatoid arthritis: a prospective cohort study.

Background: While targeting the interleukin-6 receptor (IL-6R) through the use of sarilumab (SAR) or tocilizumab (TCZ) has become a major therapeutic approach for rheumatoid arthritis (RA), direct comparisons between IL-6R inhibitors (IL-6Ris) for treating RA have not been conducted. We aimed to compare the effectiveness of subcutaneous sarilumab (SAR-SC), subcutaneous tocilizumab (TCZ-SC), and intravenous TCZ (TCZ-IV) against RA in a multicenter cohort study.

Methods: Within the target trial emulation framework, an incident new-user and active-comparator cohort design was used. The source population was the entire cohort of a multicenter prospective study (the ANSWER cohort study) in Japan from 2009 to 2023. We consecutively included patients with IL-6Ri-naïve RA who initiated treatment with SAR-SC 200 mg biweekly, TCZ-SC 162 mg biweekly, or TCZ-IV 8 mg/kg every 4 weeks as the approved starting dose and dosing interval at baseline. The primary outcome of interest was the change in the clinical disease activity index (CDAI) at 24 weeks.

Results: In total, 1001 IL-6Ri-naïve patients were included (SAR-SC 200 mg biweekly, 201 patients; TCZ-SC 162 mg biweekly, 546; TCZ-IV 8 mg/kg every 4 week, 254). The improvement in CDAI at 24 weeks (primary outcome) was statistically significantly greater in the SAR-SC group than in the TCZ-SC group (-2.53, 95% confidence interval (CI): -4.38 to -0.69, p = 0.007), but that in TCZ-IV was not significantly different from that in TCZ-SC (1.00, 95% CI: -0.68 to 2.69, p = 0.243). Similar results were noted regarding the changes in CDAI at weeks 4, 12, and 48. The retention rates at 48 weeks in SAR-SC and TCZ-IV did not significantly differ from that in TCZ-SC.

Conclusions: SAR-SC 200 mg biweekly initiation was associated with a statistically significantly greater decrease in disease activity than TCZ-SC 162 mg biweekly in IL-6Ri-naïve patients with RA. In contrast, no statistically significant differences were identified between TCZ-IV 8 mg/kg every 4 week and TCZ-SC 162 mg biweekly. However, the effect size of our findings should necessitate careful consideration of the cost difference between TCZ-SC 162 mg biweekly including its biosimilars and SAR-SC 200 mg biweekly.