Nordic Study Shows Similar Retention Rates for Biosimilar and Reference Etanercept, Infliximab

Nordic countries have had some of the highest rates of biosimilar use, and extensive registry data in these countries also allow for observational studies of biosimilar use in real-world clinical practice. A new paper, published in RMD Open, used data from 5 such registries—which included more than 2000 patients with spondyloarthritis—to assess retention rates for those treated with biosimilars or reference products of etanercept and infliximab.

In the study, biologic-naïve patients with spondyloarthritis in the 5 Nordic nations who started treatment with reference etanercept (Enbrel), reference infliximab (Remicade), biosimilar etanercept (Benepali), or biosimilar infliximab (Remsima) between 2014 and 2017 were included. Data were derived from national biologics registers in Sweden (ARTIS), Denmark (DANBIO), Finland (ROB-FIN), and Iceland (ICEBIO), as well as the regional biologics register in Norway (NOR-DMARD).

In total, 2334 patients were included; 1319 patients received infliximab (24% reference, 76% biosimilar), and 1015 patients received etanercept (49% reference, 51% biosimilar). Apart from higher concomitant disease-modifying antirheumatic drug use in the reference cohorts, there were no clinically relevant differences in baseline characteristics among the patients who started therapy with reference drugs versus biosimilars.

The investigators found that retention among patient receiving reference and biosimilar drugs was similar at 1 year:

• Reference infliximab: 62% (95% CI, 57%-68%)
• Biosimilar infliximab: 63% (95% CI, 60%-66%)
• Reference etanercept: 66% (95% CI, 61%-70%)
• Biosimilar etanercept: 73% (95% CI, 68%-78%).

Two-year data were available for infliximab, and also showed similar retention:

• Reference infliximab: 44% (95% CI, 38%-50%)
• Biosimilar infliximab: 46% (95% CI, 42%-51%).

Proportional hazard analyses showed a 5% decrease in risk of discontinuation favoring biosimilar infliximab over the reference, and a 15% decrease for biosimilar etanercept over its reference; however, the 95% CIs did not show a statistically significant decrease in risk.

While the study was limited by the fact that it did not allow for a direct comparison of efficacy, and the fact that not all countries contributed to all treatment arms due to biosimilar availability, “a strength of the present study is that confounders, such as nocebo related to the context of switching from a stable ongoing treatment with an originator to its (cheaper) biosimilar, should be minimized in a bionaïve population. Another strength is that the pooling of data from the different countries ought to reduce the risk of country-specific channeling towards originators or biosimilars,” write the authors.

Reference

Lindström U, Glintborg B, Di Giuseppe D, et al. Treatment retention of infliximab and etanercept originators versus their corresponding biosimilars: Nordic collaborative observational study of 2334 biologics naïve patients with spondyloarthritis. RMD Open 2019;5:e001079. doi: 10.1136/rmdopen-2019-001079.