Résumé
Objectives: the use of biosimilar treatments (bsDMARDs) for chronic inflammatory rheumatic diseases makes it possible to limit the direct costs of treatment, but there are still obstacles to their use, and the switch from an originator molecule (boDMARD) to a bsDMARD sometimes leads to therapeutic failure. The aim of this study was to identify the risk factors for this switch failure.Methods: this was a prospective, single-centre, open-label study including stable patients on boDMARD of Adalimumab (ADA) or Etanercept (ETN) who started bsDMARD. Rates of early discontinuation (before the 6-month follow-up visit) or late discontinuation (during the follow-up visit) and factors associated with these failures were investigated.Results: our population was predominantly rheumatoid arthritis (RA) (40%) and spondylarthritis (SpA) (45.6%), mainly on ETN (63.3%) with a mean duration of treatment of 85.6 months. Of the 180 patients included, 168 had started bsDMARD. With an average follow-up time of 7.9 months, 110 (65.5%) had maintained treatment, 31 (18.5%) had discontinued early and 27 (16%) late. Of the 58 failures, 51.7% described loss of efficacy, 31.1% intolerance and 8.6% both. 73% of failed patients switched back to boDMARD, 12% switched to bsDMARD and 15% switched to another bDMARD. 23.8% of patients had experienced an adverse event (AE), 50% of which were injection site reactions (ISRs). The presence of AEs, particularly ISR, was independently associated with early (OR=5.8; [2.3-14.6] and OR 3.8: [1.3-9.8] respectively) and late (OR 5.1; [2.0-13.4] and OR 9.4; [2.5-35.0] respectively) discontinuation of bsDMARD.Starting ADA on bsDMARD was independently associated with early discontinuation (OR 2.6; [1.0-6.5]), and association with csDMARD with late discontinuation (OR 3.0; [1.2-7.7]). In univariate analysis, diagnosis of SpA (p=0.04) and young age (p=0.05) were also associated with early failure.Conclusion: the presence of AEs and in particular ISRs was strongly associated with early and late discontinuation of bsDMARD. Improved management of ISRs could be a modifiable factor to improve maintenance of bsDMARD after switch. The high failure rate found in our study, linked to the tolerability or loss of efficacy of bsDMARD, raises questions about the real economic impact of this measure, which could be limited by an increase in the use of healthcare.