Fabrizio Cantini, Maurizio Benucci

The recent approval of reference etanercept (re-ETN) biosimilars SB4, GP2015, and HD203 produced relevant changes in the management of rheumatoid arthritis (RA), psoriatic arthritis, and ankylosing spondylitis due to the considerably lower cost of these products and the consequent savings. To review the pharmacodynamics, pharmacokinetics, efficacy, and safety of ETN biosimilars when employed as first-line therapy or after transition from re-ETN. Patients' acceptability was also addressed. The available literature was reviewed through a search of PubMed database, and abstract books of the American College for Rheumatology and European League Against Rheumatism annual meetings. SB4, GP2015, and HD203 were licensed by the US, European and South Korea regulatory agencies after the bioequivalence to re-ETN was demonstrated through pharmacodynamic and pharmacokinetic studies, and randomized, head to head, controlled trials. Based on the evidence of efficacy and safety of SB4 and HD203 in RA, and of GP2015 in psoriasis, by the extrapolation principle, the three biosimilars were approved for all indications licensed for re-ETN, and the regulatory agencies introduced the interchangeability from the originator to the biosimilar. Extrapolation of indications, and particularly interchangeability raised relevant concerns among the rheumatologists due to the low level of evidence supporting the switching strategy (or transition). Rheumatologists' concerns are oriented toward the relevant number of biosimilar discontinuations after the transition ranging from 7%-17% over a short-term follow-up period. As resulted from two studies, at least 20%-30% of the patients claimed more exhaustive information on the switching procedure. Based on the available evidence, re-ETN biosimilars may be a good option as first-line therapy, while further data are needed to definitively establish the efficacy, safety, and the economic reflexes of transitioning from re-ETN.