Background/Purpose: Biosimilars of biotechnological agents represent an important opportunity to increase accessibility to these medications. Clinicians still maintain reservations regarding the similarity of their efficacy and safety in practice. Our purpose was to evaluate the clinical consequences of a block switch of etanercept (ETN) original to biosimilar in a clinical practice setting.

Methods: The study included all patients aged 18+ treated in a Tertiary Rheumatology Department with original ETN who were switched to his biosimilar following a decison  by the hospital administration, accepted by rheumatologists. Disease activity and adverse events were evaluated at baseline (time of switch) and 3 months after and were compared using Paired samples T-test and Wilcoxon test, as appropriate. A p<=0.05 was considered statistically significant. Adaptation to the drug delivery instrument was also evaluated. Continuous variables are presented as means and categorical variables as proportions.

Results: From 98 patients treated with original ETN in our department, 89 were switched to his biosimilar. The remaining ones maintained the treatment with the reference biological product for several reasons. Twelve patients were excluded from this analysis: poor adherence to treatment (n=3), early interruption of treatment [n=3, due to surgery (n=1), respiratory infection (n=1) and suspected allergic reaction to biosimilar (n=1)] and 3 months observations still to be performed (n=6). Of the remaining 77 patients (58.4% female, mean age 55.3±11.7 years), 39% had RA, 37.7% SpA, 20.8% PsA and 2.6% JIA. Disease activity was stable over the follow up in patients with RA, PsA and SpA, as no statistically significant differences were observed in acute phase reactants, patient or physician global assessment between the two time points. Minor adverse events were reported by 2 patients (pain and local cutaneous reaction) and another 2 report impression of disease exacerbation that was not confirmed by clinical and analytical evaluation. Two patients reported minor infections. Good adaptation to the drug delivery instrument was reported by 93% of patients.

Table 1. Acute phase reactants, disease activity, joint count and patient and physician global assessment through follow-up

IQR – Interquartile range; PhGA physician global assessment; PtGA– patient global assessment; SD – standard deviation; f median(IQR); § mean(SD). *Only for RA and PsA patients (n=46). None of the differences was statistically significant by paired tests.

Conclusion: The non-medical switch from ETN to his biosimilar in this group of patients followed in routine care did not affect the overall efficacy and safety of treatment. However, these observations only cover 3 months of follow up. A longer observational period is necessary to assess the long-term response.