Rheumatologists' perceptions of biosimilar use in Spain: the CUSTODIAN study

To explore rheumatologists' experiences and perceptions regarding the use of biosimilars in rheumatoid arthritis (RA) management.

Descriptive and exploratory survey-based study conducted between March and April 2025 in Spain. Eligible participants were rheumatologists with ≥10 years of experience in Rheumatology and ≥5 years using biosimilars for RA, including at least two different molecules. The survey included 85 items across four sections: participant and patient characteristics, biosimilar use patterns, rheumatologists' perceptions, and reported patient attitudes. Responses were anonymous. Subgroup analyses were not pre-specified in the statistical analysis plan.

Thirty rheumatologists participated (mean age 49 years; 53.3% female), with a mean of 20.2 years of Rheumatology experience. All routinely prescribed biologics, treating a mean of 192.1 patients with RA, of whom 129 were treated with a biosimilar for ≥6 months. bsAdalimumab (bsADA) was the most widely used biosimilar. Most participants initiated biosimilars in patients naïve to biologics. Switching from reference molecules was less common and multi-switches were not common. Six months after initiation or switching, rheumatologists reported stable or improved disease activity in most patients, with no perceived worsening in experienced or switched patients. Nearly all participants considered biosimilars as safe and effective as the reference molecules, although patient preference for the reference molecules and concerns about safety were cited as barriers. Sustainability and cost savings were important drivers for adoption.

This survey-based study provided valuable insights into prescribing behaviors and attitudes, supporting strategies to optimize biosimilar implementation in Spain, highlighting the need for educational interventions to address residual concerns.