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Original article
Treatment retention of infliximab and etanercept originators versus their corresponding biosimilars: Nordic collaborative observational study of 2334 biologics naïve patients with spondyloarthritis
  1. Ulf Lindström1,
  2. Bente Glintborg2,3,
  3. Daniela Di Giuseppe4,
  4. Dan Nordström5,
  5. Sella Aarrestad Provan6,
  6. Bjorn Gudbjornsson7,
  7. Johan Askling4,
  8. Merete Lund Hetland2,3,
  9. Kalle Aaltonen8,
  10. Niels Steen Krogh9,
  11. Arni Jon Geirsson10 and
  12. Lennart T H Jacobsson1
  1. 1Department of Rheumatology and Inflammation Research, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
  2. 2DANBIO and Copenhagen Center for Arthritis Research (COPECARE), Center for Rheumatology and Spine Diseases, Centre of Head and Orthopedics, Rigshospitalet Glostrup, Glostrup, Denmark
  3. 3Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
  4. 4Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
  5. 5Department of Medicine, Helsinki University and Helsinki University Hospital, Helsinki, Finland
  6. 6Rheumatology, Diakonhjemmet Hospital, Oslo, Norway
  7. 7Centre for Rheumatology Research, University Hospital and Faculty of Medicine, University of Iceland, Reykjavik, Iceland
  8. 8Pharmaceuticals Pricing Board, Ministry of Social Affairs and Health, Helsinki, Finland
  9. 9Zitelab Aps, Copenhagen, Denmark
  10. 10Department of Rheumatology, University Hospital, Reykjavik, Iceland
  1. Correspondence to Dr Ulf Lindström; ulf.lindstrom{at}


Objective Although clinical trials support equivalence of originator products and biosimilars for etanercept and infliximab, real-world studies among biologics-naïve patients with spondyloarthritis (SpA) are lacking. The objectives were to compare treatment retention in biologics-naïve patients with SpA starting either the originator product or a biosimilar of infliximab and etanercept, and to explore the baseline characteristics of these patients.

Methods Patients with SpA (ankylosing spondylitis/non-radiographical axial SpA/undifferentiated SpA), starting infliximab or etanercept as their first-ever biological disease-modifying antirheumatic drug during January 2014–June 2017 were identified in five Nordic biologics–rheumatology registers. Baseline characteristics were retrieved from each registry; comorbidity data were identified through linkage to national health registers. Country-specific data were pooled, and data on infliximab and etanercept were analysed separately. Comparisons of treatment retention between originators and biosimilars were assessed through survival probability curves, retention rates (2 years for infliximab/1 year for etanercept) and Hazard Ratios (HR).

Results We included 1319 patients starting infliximab (24% originator/76% biosimilar), and 1015 patients starting etanercept (49% originator/51% biosimilar). Baseline characteristics were largely similar for the patients treated with the originators compared with the corresponding biosimilars. Survival probability curves were highly similar for the originator and its biosimilar, as were retention rates: infliximab 2-year retention originator, 44% (95% CI 38% to 50%)/biosimilar, 46% (95% CI: 42% to 51%); and etanercept 1-year retention originator, 66% (95% CI 61% to 70%)/biosimilar, 73% (95% CI 68% to 78%). HRs were not statistically significant.

Conclusion This observational study of biologics-naïve patients with SpA from five Nordic countries showed similar baseline characteristics and very similar retention rates in patients treated with originators versus biosimilars, for both infliximab and etanercept, indicating comparable effectiveness in clinical practice.

  • ankylosing spondylitis
  • anti-TNF
  • epidemiology
  • spondyloarthritis
  • outcomes research

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  • UL and BG are joint first authors.

  • Contributors UL, BG and LJ contributed to the study design. DDG performed the analysis of raw data. All authors contributed to the interpretation of the results and in the preparation of the manuscript.

  • Funding This study was partly funded by grants from Nord-Forsk and FOREUM.

  • Competing interests BG: grant/research support from Biogen, Pfizer and AbbVie. JA: Karolinska Institutet (through JA) has or has had research agreements with the following pharmaceutical companies, mainly in the context of the ARTIS national safety monitoring programme for rheumatology biologicals: Abbvie, BMS, MSD, Eli Lilly, Pfizer, Roche, Samsung Bioepis and UCB; Karolinska Institutet has alo received remuneration for JA participating in ad boards arranged by Lilly, Novartis and Pfizer. DN: grant/research support from MSD, Pfizer; consultant for AbbVie, BMS, MSD, Novartis, Roche, Pfizer and UCB; speakers' bureau: Novartis and UCB. SP: consultant for Novartis; speakers' bureau: Lilly. MH: grant/research support from BMS, MSD, AbbVie, Roche, Novartis, Biogen and Pfizer; consultant for Eli Lilly; speakers' bureau Orion Pharma, Biogen, Pfizer, CellTrion, Merck and Samsung Bioepis. LJ: lecture and consulting fees from Pfizer, Abbvie, Novartis, Eli-Lily and Janssen.

  • Patient consent for publication Not required.

  • Ethics approval The appropriate ethical committees and/or data protection committees in each country approved of the study (approval codes for Sweden: 2015/1844-31/2; Denmark: RH-2015–209, I-suite 04145; Norway: 2011/1339 and 2017/243; Finland: 73/13/03/00/2014; and Iceland: VSNb2017010049/03.01). Individual patient consent was not required.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.

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