Pharmacist Substitution of Biological Products: Issues and Considerations

Biosimilars are biological products that are highly similar to their biological reference products, notwithstanding minor differences in clinically inactive components. However, unlike generics of small-molecule drugs, biosimilars are not identical to their reference products, since each manufacturer uses unique cell lines and processes, and these lead to slight structural differences between products. Because these structural variations can lead to differences in clinical response, clinical studies demonstrating biosimilarity are required before and robust pharmacovigilance after approval. Although the FDA has not yet issued formal guidance on interchangeable biosimilars, higher standards of similarity will be required in order to achieve an interchangeable designation. In this commentary, we review the differences between generics and biosimilars, describe their respective regulatory approval pathways, discuss interchangeability and substitution, and review substitution of interchangeable biosimilars, focusing on key professional considerations for pharmacists.