Biosimilars in chronic inflammatory diseases: facts and remaining questions 5 years after their introduction in Europe

INTRODUCTION: Five years after the launch of the first infliximab biosimilar, biologics have found their place in the treatment of chronic inflammatory conditions, but there are remaining questions. This is a review of the introduction of antibody biosimilars in Europe; the reasons for their success and how biosimilar hesitancy was quailed. AREAS COVERED: We provide an overview of the concepts of biosimilarity, extrapolation, and interchangeability, using examples in rheumatology and gastroenterology for illustration. A review of the evidence collected from switching studies using robust designs is included. Remaining questions such as 'inter-switching' are also discussed. EXPERT OPINION: Biosimilars have democratized access to powerful medicines. Efficacy and safety studies provided reassuring data, but knowledge gaps persist. The availability of so-called 'bio-betters' might open new avenues and change clinical practice.