An analysis of US claims data found that prevalent (as of 2017) users of the infliximab reference product (Remicade) had the highest adherence rates compared to naïve originator users, prevalent biosimilar users, and naïve biosimilar users over 18 months of follow-up.
An analysis of US claims data found that prevalent (as of 2017) users of the infliximab reference product (Remicade) had the highest adherence rates compared to naïve originator users, prevalent biosimilar users, and naïve biosimilar users over 18 months of follow-up. Factors associated with adherence included depression, previous hospitalizations, use of other biologics, disease treated, and age.
In the United States, there are 4 FDA-approved infliximab biosimilars, 3 of which have launched on the market. Infliximab is a tumor necrosis factor-alpha inhibitor used to treat chronic inflammatory diseases. Although clinical trials have demonstrated that switching from the reference product to a biosimilar is safe and effective, “there are limited real-world data comparing their patterns of use and adherence,” according to the investigators. They added that suboptimal adherence (defined as an adherence less than 80%) is common among patients with chronic inflammatory diseases, especially those treated with biologics.
The retrospective cohort study used IBM Marketscan US commercial and Medicare claims data from 2015 to 2018 and established 3 cohorts of patients treated with infliximab products: infliximab-naïve biosimilar users (n = 96 patients), infliximab-prevalent biosimilar users (n = 223), infliximab-naïve originator users (n = 2149), and infliximab-prevalent originator users (n = 10,970). Naïve vs prevalent use was defined by use of infliximab products prior to the baseline which was set in 2017, since there were 3 infliximab biosimilars approved between 2016 and 2017.
There were differences in baseline characteristics between the cohorts. Prevalent biosimilar users were older than naïve originator users, who were the youngest. A greater proportion of biosimilar users were located in the Western region of the United States, and more originator users were from the South and Midwest. Among biosimilar users, 51% were patients with rheumatoid arthritis (RA) compared to 39% of originator users. Patients with inflammatory bowel disease (IBD) made up 46% and 36% of biosimilar and originator users, respectively. A greater percentage of the naïve groups had previously used other biologics (41%) compared to prevalent users (11%).
Adherence Highest in Prevalent Remicade Users
Over the follow-up time, the proportion of patients with optimal adherence (proportion of days covered more than 80%) decreased in all 4 groups. At 12 months, 73% of prevalent originator users, 52% of naïve originator users, 46% of prevalent biosimilar users, and 43% of naïve biosimilar users had optimal adherence. By 18 months, optimal adherence rates had declined to 64% of prevalent originator users, 48% of naïve originator users, 36% of prevalent biosimilar users, and 41% of naïve biosimilar users. Prevalent originator users had the highest adherence rate at both time points.
A lower percentage of prevalent originator users compared to the other groups switched to a biosimilar or another biologic during the follow-up period: 13% of prevalent originator users, 16% of naïve originator users, 29% of prevalent biosimilar users, and 23% of naïve biosimilar users switched. The authors commented that a large percentage of the switching originator users switched to another biologic, whereas most of the switching biosimilar users switched to the reference product.
Age and Depression Among Factors Associated With Adherence
The authors examined associations between baseline factors and adherence. Adherence differed by age: patients between the ages of 55 and 64 had better adherence at 12 and 18 months compared to those under 35. Patients with IBD had greater adherence than those with RA, and patients who had depression, a hospitalization for any cause, and those who were using other biologics had lower adherence than those who did not.
The higher adherence in patients with IBD compared to RA could be due to the “high severity and malaise of IBD over RA,” the authors said, or because a larger proportion of patients with IBD compared to RA were originator users, who overall had higher adherence in their study.
Using naïve originator users as the reference, prevalent originator users were significantly more likely to have optimal adherence at 12 and 18 months and prevalent biosimilar users less likely to have optimal adherence at 12 months only. There was no significant difference in optimal adherence between naïve biosimilar users and naïve originator users at either time point.
The investigators wrote, “further studies with large sample sizes are needed to evaluate the adherence of [infliximab] biosimilar users.” They theorized that prevalent originator users may have had the highest adherence and lowest rate of switching in part because they had passed through the “early treatment phase where discontinuations due to side effects, tolerability, and lack of efficacy are more common.”
The high rate of switching among prevalent biosimilar users, they said, could have been due to a “transitory” use of a biosimilar or a “strong preference” for the originator. They also said that similar therapeutic effects between the originator and biosimilar could have led some patients to alternate between treatments. However, this was not captured by their current study and they plan to analyze alternation between originator and biosimilar in the future.
Alanaeme CJ, Sarvesh S, Li CY, Bernatsky S, Curtis JR, Yun H. Adherence patterns in naïve and prevalent use of infliximab and its biosimilar. BMC Rheumatol. 2022;6(1):65. doi:10.1186/s41927-022-00295-7