Predictive Factors for Rheumatoid Arthritis Flare After Switching From Intravenous to Subcutaneous Formulation of Tocilizumab in Real-World Practice

BACKGROUND: To evaluate the incidence and related factors of rheumatoid arthritis (RA) flares after switching from intravenous tocilizumab (TCZ-IV) to subcutaneous tocilizumab (TCZ-SC) injection in stable RA patients. METHODS: We retrospectively evaluated the medical records of stable RA patients who used TCZ-IV for more than 6 months and switched to TCZ-SC between January 2013 and April 2020. RA flare was defined as an increase of more than 1.2 in the RA disease activity as assessed by the disease activity score in 28 joints. The factors associated with RA flare were evaluated by logistic regression analysis. RESULTS: Among 106 patients treated with TCZ-IV for > 6 months, 37 patients were switched to TCZ-SC after the acquisition of remission or low disease activity. RA flares occurred in 11 (29.7%) of patients who switched TCZ-SC. Results from the multivariable logistic analysis revealed that the dose of TCZ-IV per weight at switching (odds ratio [OR], 20.70; 95% confidence interval [CI], 2.22–192.84; P = 0.008) and methotrexate (MTX) non-use (OR, 8.53; 95% CI, 1.21–60.40; P = 0.032) were associated with the risk of RA flares after switching to TCZ-SC. Interestingly, most patients who switched back to TCZ-IV had their RA activity controlled again. CONCLUSION: MTX non-use and high dose of TCZ-IV per weight were associated with a risk of RA flare after switching to TCZ-SC. RA patients with these factors need to be carefully observed for flare after switching from TCZ-IV to TCZ-SC.