Extrapolation and Interchangeability of Infliximab and Adalimumab in Inflammatory Bowel Disease

Infliximab and adalimumab biosimilars have been approved by the FDA and European Medicines Agency and have already been introduced to the international market. Availability into the US market is imminent. Biosimilars are highly similar to the reference biologic product but should not be referred to as, nor equated with, generic medications as no two biosimilars can ever be identical. Regulatory pathways for biosimilar approval consider the totality of evidence for biosimilar approvals, but the preponderance of development relies on analytic and functional testing and allows extrapolation between indications to reduce the financial burden of completing comparative clinical trials for each indication. Neither CT-P13 (infliximab biosimilar) nor ABP 501 (adalimumab biosimilar) was clinically tested in patients with inflammatory bowel disease prior to being submitted for approval by regulatory agencies. The body of available evidence suggests that these drugs will perform similarly to their originators. The pathway for interchangeability of biosimilars has yet to be clarified by federal regulators and currently remains determined by states within the USA. However, preliminary data suggests that switching from originator to biosimilar is safe with minimal differences in clinical efficacy.