Background/Purpose: The availability of biosimilars as non-proprietary versions of established biologic disease-modifying anti-rheumatic drugs (bDMARDs) has increased around the world. Since April 2017 both the originator and a biosimilar for etanercept have been available for use in Australia. This study aimed to model effectiveness of etanercept originator or biosimilar in reducing DAS28CRP in patients with RA, PsA or AS treated with either drug as first-line bDMARD as well as describe persistence on etanercept originator or biosimilar as first-line bDMARD in patients with RA, PsA or AS.

Methods: Clinical data were obtained from the Optimising Patient outcomes in Australian rheumatoLogy (OPAL) dataset, derived from electronic medical records. Eligible patients with RA, PsA or AS who initiated etanercept originator (n=977) or biosimilar (n=552) as first-line bDMARD between 1 April 2017 and 31 March 2021 were identified. Propensity score matching was performed to select patients on originator (n=280) or biosimilar (n=170) with similar characteristics in terms of diagnosis, disease duration, joint count, age, sex and concomitant medications. Data on clinical outcomes were recorded at 3 months after baseline, and then at 6-monthly intervals. Outcomes data that were missing at a recorded visit were imputed and propensity scores were re-calculated to include imputed outcomes data at baseline including DAS28CRP.

Effectiveness of the originator, relative to the biosimilar, for reducing DAS28CRP over time was modelled in the matched population using linear mixed models with both random intercepts and slopes to allow for individual heterogeneity. Time was modelled as a combination of linear, quadratic and cubic continuous variables. Individuals were weighted using inverse probability of treatment weights to ensure comparability between treatment groups. The average weighted baseline DAS28CRP were 4.95 and 4.94 for the originator and biosimilar, respectively.

Persistence on the originator or biosimilar was analysed using survival analysis (log-rank test).

Results: Reduction in DAS28CRP was associated with both time and etanercept originator treatment (Table 1). The conditional R-squared for the model was 0.28. The average model-predicted DAS28CRP at 3 months, 6 months, 9 months and 12 months were 3.0 and 3.3, 2.5 and 2.8, 2.3 and 2.5, and 2.1 and 2.3 for the originator and biosimilar, respectively, indicating a clinically meaningful effect of time for patients on either drug and an additional modest improvement for patients on the originator.

Median time to 50% of patients stopping treatment was 24.6 (16.8, 35.9) months for the originator and 24.1 (15.2, 32.2) months for the biosimilar (p=0.72). An adverse event was the reason for discontinuing treatment in 39 patients (11.4%) on the originator and 20 patients (13.4%) on the biosimilar.

Conclusion: Analysis using a large national real-world dataset showed treatment with either the etanercept originator or the biosimilar was associated with a reduction in DAS28CRP over time, with the originator being associated with a further modest reduction in DAS28CRP that was not clinically significant. Persistence on treatment was not different between the two drugs.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/modelling-of-disease-activity-in-patients-with-inflammatory-arthropathies-treated-with-etanercept-originator-or-biosimilar-as-first-line-biologic-a-real-world-observational-study-using-the-opal-datas/