Nijmegen, The Netherlands—Because biosimilars, by definition, have no clinically meaningful differences from the already approved biologic medicine, patients theoretically should be able to detect little variation between them. 

Yet, a new study in Arthritis & Rheumatology found that one fourth of patients with rheumatoid arthritis, psoriatic arthritis, or ankylosing spondylitis who switched from the reference drug infliximab, marketed as Remicade (REM), to the biosimilar infliximab, CT-P13, discontinued the new drug over 6 months of follow-up.

The reasons? Mostly subjective health complaints, according to the study led by researchers from Sint Maartens Clinic in the Netherlands.

The multicenter prospective cohort study included 192 of 222 REM-treated patients who agreed to transition to CT-P13. Over 6 months of follow-up, 24% of patients discontinued CT-P13, with 37 patients restarting REM, seven patients switching to another biologic, and three patients maintaining biologic-free status. 

At the same time, however, monitoring indicated that DAS28-CRP remained stable from baseline to month 6: 2.2 (SD 0.9) to 2.2 (SD 0.8) (difference 0.0, 95% CI, -0.1 to 0.2). BASDAI increased from 3.8 (SD 2.0) to 4.3 (SD 2.1) (difference +0.5, 95% CI, 0.1 to 0.9). CRP and (anti-) infliximab levels did not change, the authors report. 

“Just prior to CT-P13 discontinuation, DAS28-CRP components, tender joint count and patients’ global disease activity, and BASDAI were increased compared to baseline,” researchers point out. “Most frequently reported [adverse events] were arthralgia, fatigue, pruritus and myalgia.”

The study notes that a shorter REM infusion interval at baseline, with a hazard rate of 0.77, was predictive for CT-P13 discontinuation.

“In our cohort, a quarter of patients discontinued CT-P13 during six months follow-up, mainly due to an increase in subjective tender joint count and patients’ global disease activity and/or subjective AEs, possibly explained by nocebo and/or incorrect causal attribution effects,” the authors conclude.

“As a result, communication between clinicians and patients seems to be the determining factor of the success of transitioning to a biosimilar in daily practice,” added lead author Lieke Tweehuysen, MD.