Clinical efficacy and nocebo effect following non-medical biosimilar switch in patients with inflammatory bowel disease: A prospective observational study.

Background: We aimed to evaluate clinical efficacy, biomarker activity, therapeutic drug monitoring (TDM), adverse events (AEs), and nocebo effect in inflammatory bowel disease (IBD) patients who underwent non-medical biosimilar switching.

Methods: A prospective observational study of consecutive IBD patients who underwent biosimilar switch. Disease activity, biomarkers, TDM, and AEs, including the nocebo effect were captured 8 weeks before switch, at the time of switch (baseline),12 and 24 weeks after the switch.

Results: 210 patients were included [81.4% had Crohn's disease (CD), the median age at inclusion: 42 years (IQR 29-61)]. There was no significant difference in the rates of clinical remission at week 8 before switch, baseline, week12, and 24 after switch: 89.0%,93.4%,86.3%,and 90.8%,p = 0.129. The biomarker remission rates were not significantly different; CRP:81.3%,74.7%,81.2%,73.0%,p = 0.343; fecal calprotectin: 78.3%,74.5%,71.7%,76.3%,p = 0.829. The rates of maintaining therapeutic levels (84.7%,83.9%,83.0%,85.3%,p = 0.597) and prevalence of positive anti-drug antibodies remained unchanged. Drug persistence at 12 week of switch was 97.1%, regardless of disease phenotype and originator. The nocebo effect was observed in 13.3%. The discontinuation rate was 4.8%.

Conclusion: Despite a significant number of early nocebo complaints within the first 6 months after the biosimilar switch, no significant changes were found in clinical efficacy, biomarkers, therapeutic drug level, or anti-drug antibodies.