Biosimilars

Biologic therapy for treatment of rheumatoid arthritis (RA) has evolved considerably over the past 20 years. Biosimilar development continues to accelerate at a frenetic pace worldwide. Initial regulatory efforts were developed within the EU and subsequent guidelines have now evolved in over 20 countries. Biosimilars by definition are highly similar, with ‘comparable quality, safety, and efficacy’ (EMA) and ‘no clinically meaningful differences in safety, purity, and potency’ (FDA) to the reference product. Development and manufacturing are based on reverse engineering of the reference product as only the primary amino acid sequence is known. Testing of primary, secondary, tertiary, and quaternary structure, binding pharmacokinetics, and stability is required. Characterization of post-translational modifications and biologic function, pharmacokinetics, evaluation of immunogenicity, and at least one comparative efficacy clinical trial are major requirements for regulatory approval. Clinical trials to assess biosimilarity are required in only one clinical indication and may be extrapolated to other indications for which the reference product is approved. Both single and multiple switching trials (between biosimilar and reference product) have yielded consistent results across numerous patient populations and diseases, with no evidence of detrimental outcomes. Two prospective large observational series (Danbio and Nor-Switch) have similarly assessed non-medical switching. Several open-label switching studies have revealed equivalent efficacy, safety, and discontinuation rates but real-world studies have raised concerns about potential nocebo responses.