Background A high percentage of patients treated with TNF antagonists discontinue therapy mainly due to lack of efficacy or side effects. Recent studies of stable infliximab (IFX) patients switched to biosimilar infliximab (INB) seem to suggest similar safety and efficacy outcomes as IFX^1,2. However, these studies often have small sample sizes, short follow-up periods and, where reported, high discontinuation rates post-switch.

Objectives To demonstrate long-term retention patterns of stable Canadian rheumatic disease (RD) patients treated with originator IFX.

Methods We conducted a population cohort study using IMS health™|Brogan's longitudinal Canadian patient claims database, the largest such database in Canada. The analysis captured a robust sample of thousands of claims from private insurers across Canada, and public claims from Ontario and Quebec. The retention analysis included RD patients with: a) an initial IFX claim during the selection period of Jan 2008-May 2015; b) absence of IFX claims in the 12 months prior to the initial claim; c) ≥1 claim for any drug other than IFX drug during that 12-month period; and d) ≥1 claim in the 4 months following the end of the longitudinal patient tracking period. Retention was measured at 12-month intervals and analyzed accordingly. Unadjusted odds ratios were then calculated based on retention data and 10 pairwise comparisons were calculated at the 95% confidence interval.

Results The analysis captured 3,131 IFX RD patients in the selection period of which 1,822 had ≥2 years of claims history and had been on IFX for ≥1year. The table below demonstrates that the patient's probability of being retained on IFX in the subsequent 12 months increases concurrently with elapsed time on IFX. Specifically for patients on IFX for 2, 3, 4 and 5 years, retention in subsequent 12 month periods was significantly higher than for patients retained for 1 year (P<0.005).

Conclusions Real world patients treated with IFX have excellent long term treatment retention. Incrementally longer time on IFX appears to be predictive of better future retention. This becomes statistically significant for patients who are retained on therapy for ≥2 years. Stability on IFX is a factor to consider when deciding whether to switch stable patients to another biologic (including biosimilars) for non-medical reasons. Studies in which stable patients receiving IFX are switched to INB for non-medical reasons have claimed similar safety and efficacy outcomes as IFX, albeit with much higher INB discontinuation rates^1,2. Safety and efficacy outcomes need to consider an intention to treat population that includes patients who discontinue INB after switching and retention results need to be further investigated with larger sample sizes and longer follow-up periods to better understand what drives post-switch discontinuation from INB.

1. J Crohns Colitis.2015Dec30 Advanced Access.

2. Expert Opin Biol Ther.2015Dec;15(12):1677–83

Disclosure of Interest M. Khraishi Consultant for: Janssen Inc. Canada, J. Foley: None declared, E. Stein: None declared