Evaluation of the nocebo effect after switching from etanercept or adalimumab originator to a biosimilar: a retrospective study of patients with inflammatory rheumatism.

Objectives: Despite significant savings with biosimilars, their negative perception can lead to the occurrence of a nocebo effect (NE), therefore we aimed to quantify the NE in inflammatory rheumatism after switching from adalimumab or etanercept originators to biosimilars.

Methods: This retrospective study was conducted in 4 hospitals in Normandy, France between January 2018 and July 2022. The study included patients with rheumatoid arthritis or spondyloarthritis in remission under adalimumab or etanercept originators before switching to biosimilars. The occurrence of a NE was considered in patients who did not maintain biosimilars at 12 months and who presented a subjective adverse event (AE). A comparative analysis of the quantitative data collected before and after switching was performed. The AE that led to biosimilar discontinuation was identified. Additional analyses were performed to identify potential risk factors for the occurrence of a NE.

Results: Among 183 patients included,13.1% presented a NE. Objective AEs were observed, including rheumatism reactivation (15.3%), intolerance (8.2%), infection (1.6%) and allergic reactions (0.5%). Morning stiffness duration was significantly different before and after the switch in the spondyloarthritis group (p=0.01). No risk factors were associated with the occurrence of a NE within the limits of the studied parameters.

Conclusions: The occurrence of a NE after switching to a biosimilar remains acceptable. It appears less frequent when the switch is supervised by the practitioner rather than being systematic (up to 33% in some countries). A shared medical decision seems to be essential in a subset of patients, which remains to be defined.