Interchangeability (Biosimilars)
A regulatory determination that a biosimilar can be substituted for the reference product at the pharmacy level without prescriber intervention. Interchangeability requires additional switching studies beyond standard biosimilar approval to demonstrate that alternating between products produces no adverse effects.
Technical Context
Under the BPCIA, an interchangeable biosimilar can be substituted for the reference product at the pharmacy level without prescriber intervention (similar to generic drug substitution for small molecules). Interchangeability requires demonstrating that switching between the biosimilar and reference product does not increase risk or reduce efficacy compared to continuous use of the reference product — typically through a switching study where patients alternate between products multiple times. The first interchangeable biosimilar (insulin glargine-yfgn, Semglee) was approved in 2021. For peptide biologics, interchangeability determinations could significantly impact market dynamics by enabling automatic substitution. State pharmacy laws governing biosimilar substitution vary and add another layer of regulatory complexity.