Patient-Reported Outcomes in Rheumatoid Arthritis: A Key Consideration for Evaluating Biosimilar Uptake?

Purpose: This review aims to provide an overview of the impact of TNFis biosimilars, with marketing authorization, in patient-reported outcome measures (PROMs) scores and explore how PROMs endpoints might add value in biosimilars uptake in RA patients. Patients and Methods: A comprehensive search of Medline, Scopus, Lilacs, and CINAHL databases was performed for papers published between January 2012 and December 2021. For inclusion, studies had to be prospective, published in a peer-reviewed journal, published in English or Spanish language; studies using PROMs as an outcome measure. After screening title and abstracts and assessing the remaining full texts fulfilling the inclusion criteria, 31 papers were used in this narrative review. Results: PROMs were used as secondary outcomes in included studies. The most frequently employed domains to assess biosimilar efficacy include physical function, patient global assessment (PtGA), health-related quality of life (HRQoL), and fatigue. The results of randomized clinical trials uniformly showed that mean change in PROMs scores is comparable between biosimilar and reference biologic treatment groups. However, open-label and real-world studies revealed high rates of discontinuation of therapy, mainly for subjective worsening of disease activity or non-specific adverse events. Even without objective clinical evidence of inflammation, patients who are considered to have active disease (higher scores on PtGA) have higher discontinuation rates of biosimilars. The available information suggests that the nocebo effect is the most likely cause for the discontinuation of biosimilars. Conclusion: There is scarce literature surrounding the impact of biosimilars in PROMs, especially in open-label studies. In real-life studies, biosimilars have a higher discontinuation rate than reference products. TNFis biosimilars treatment efficacy in RA depends on disease activity and other factors such as PtGA and fatigue. The nocebo effect is the best explanation for biosimilar's discontinuation.