Switching and Discontinuation Patterns Among Patients Stable on Originator Infliximab Who Switched to an Infliximab Biosimilar or Remained on Originator Infliximab.

Objective: To compare switching and discontinuation patterns of patients stable on originator infliximab (IFX) who switched to an IFX biosimilar (switchers) or remained on originator IFX (continuers) in the United States.

Methods: Symphony Health Solutions' Patient Transactional Datasets (10/2012-03/2019) were used to identify adults with ≥2 claims for either rheumatoid arthritis (RA), psoriatic arthritis, plaque psoriasis, ankylosing spondylitis, or inflammatory bowel disease (IBD); and ≥1 claim for originator or biosimilar IFX. The index date was the first IFX biosimilar claim for switchers or a random originator IFX claim for continuers. All patients were required to have ≥5 originator IFX claims during the 12 months pre-index (prevalent population). The subset of patients with ≥12 months of observation prior to the first originator IFX claim was also analyzed (incident population). Switchers were matched 1:3 to continuers. Discontinuation was defined as having ≥120 days between 2 consecutive index treatment claims.

Results: Prevalent switchers (N=1109) were 3.57-times more likely than continuers (N=3327) to switch to another originator biologic (hazard ratio [HR]=3.57, p<0.001). Of 249 prevalent switchers who switched to another originator biologic, 200 (80.3%) switched back to originator IFX. Incident switchers (N=571) were 2.55-times more likely than continuers (N=1713) to switch to another originator biologic (HR=2.55, p<0.001). Of 118 incident switchers who switched to another originator biologic, 90 (76.3%) switched back to originator IFX. Prevalent switchers were 1.25-times more likely than continuers to discontinue index therapy (HR=1.25, p<0.001). Similar results were observed in RA (prevalent population; switching: HR=3.49, p<0.001; discontinuation: HR=1.23, p=0.009) and IBD (prevalent population; switching: HR=3.82, p<0.001; discontinuation: HR=1.29, p=0.003) subgroups.

Conclusion: Patients switching from originator to biosimilar IFX were more likely to switch to another originator biologic (notably back to originator IFX) and discontinue index treatment than those remaining on originator IFX; however, reasons for switching are unknown.