Safety, efficacy and immunogenicity of switching from innovator to biosimilar infliximab in patients with spondyloarthritis: a 6-month real-life observational study

Biosimilar infliximab (INX) was recently approved by the European Medicine Agency for the treatment of rheumatoid arthritis, ankylosing spondylitis (AS), Crohn's disease, ulcerative colitis, psoriatic arthritis (PsA), and psoriasis on the grounds that its pharmacokinetics, safety, and efficacy were comparable to those of innovator INX. The aim of this study was to investigate the real-life efficacy, safety, and immunogenicity of switching from innovator to biosimilar INX in patients with spondyloarthritis (SpA). Forty-one patients attending three Italian rheumatology centres with a previous diagnosis of SpA and clinically inactive or moderate disease activity (ASDAS-CRP < 2.1; 22 with AS, five with enteropathic arthritis, 10 with PsA, and four with undifferentiated SpA), who had been treated for more than 6 months with innovator INX in accordance with the ASAS/EULAR guidelines, were switched to biosimilar INX for pharmaco-economic reasons (Tuscany Law No. 450 of 7 April 2015) and followed up for 6 months. A record was kept of their BASDAI, BASFI, ASDAS-CRP, DAS28-CRP (in the presence of peripheral disease), MASES, VAS pain scores, the duration of morning stiffness, and adverse events (AEs). At the time of the switch, the patients had a median age of 50.9 years (range 23-80), a median disease duration of 124.5 months (range 14-372), and a median duration of treatment with innovator INX of 73.7 months (range 6-144). After 6 months of biosimilar INX therapy, there were no statistical differences in their median BASDAI (2.73 ± 1.5 vs. 2.6 ± 1.3, p = .27), BASFI (2.34 ± 1.3 vs. 2.17 ± 1.2, p = 0.051), ASDAS-CRP (1.35 ± 0.3 vs. 1.28 ± 0.2, p = 0.24), DAS28-CRP (2.66 ± 0.67 vs. 2.67 ± 0.35, p = 0.92), MASES (0.35 ± 0.7 vs. 0.17 ± 0.4, p = 0.08), or VAS pain scores (18 ± 14.7 vs. 16.7 ± 11.3, p = 0.55), whereas the median duration of morning stiffness had significantly decreased (7.2 ± 6.9 vs. 5.8 ± 6, p = 0.02). Furthermore, there was no change in circulating INX (4.22 ± 2.89 vs 4.84 ± 2.86 μg/mL, p = 0.80) or anti-INX antibody levels (27.76 ± 17.13 vs 27.27 ± 17.28 ng/mL, p = 0.98). The switch from innovator to biosimilar INX in this Italian multicentre SpA cohort was not associated with any statistically significance differences in efficacy, adverse events or anti-drug antibody level.