What are Biosimilars?

Biologics for HCPs

January 7, 2026

What are Biosimilars?

A biosimilar is a biological medicine that is highly similar to an already approved reference medicine in terms of structure, biological activity, efficacy, safety and immunogenicity.1

What are Biosimilars?

BIOLOGICS

  • Made by or extracted from living organisms, tissues, or cells
  • Innovative treatments that have transformed the lives of millions of patients with disabling or life-threatening diseases
  • Different batches of the same biological medicine may show a small degree of variability

BIOSIMILAR

  • Made by or extracted from living organisms, tissues, or cells
  • Matches the reference medicine in terms of safety, efficacy, quality and clinical outcome
  • A successor to a ‘reference medicine’ for which the patent has expired and exclusivity has been lost

GENERIC

  • Made through chemical synthesis by combining specific chemicals
  • A copy of a ‘reference medicine’ for which the patent has expired and exclusivity has been lost
  • A small molecule which can be analyzed to determine all its components and shown to be identical to the originator

The term ‘biosimilar’ is recognised and designated by both the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA).2,3 Regulatory bodies require a robust and comprehensive collation of data for a biosimilar to be approved.

This review of comparability focuses on demonstrating that the biosimilar is highly similar to the reference medicine. It includes a step-wise evaluation that begins with extensive comparative analytical and functional studies. Clinical data, typically including a comparative clinical pharmacology study and often a comparative clinical efficacy and safety study, is also required to address any residual uncertainties from earlier analyses.2,3

CONCEPTS OF BIOSIMILARS1,2,4

A table of definitions for some key terms related to biosimilars. A clear understanding of this terminology is essential for navigating the topic of biosimilar medicines.

BiologicBiologics are complex, large-molecule medicines derived from living cells or produced through biological processes.
BiosimilarA biological medicine that is highly similar to an already approved reference medicine in terms of structure, biological activity, efficacy, safety and immunogenicity.
ExtrapolationExtension of the efficacy and safety data from a therapeutic indication for which the biosimilar has been clinically tested to another therapeutic indication approved for the reference medicine.
GenericA medicine that is developed to be the same as a medicine that has already been authorised. Its authorisation is based on efficacy and safety data from studies on the authorised medicine. A company can only market a generic medicine once the 10-year exclusivity period for the original medicine has expired. 
InterchangeabilityThe ability to exchange one medicine for another medicine that is expected to have the same clinical effect.
MicroheterogeneityMinor molecular variability among biological substances due to natural biological variability and slight alterations to production methods.
SubstitutionPractice of dispensing one medicine instead of another equivalent and interchangeable medicine at pharmacy level without consulting the prescriber.
SwitchingWhen the prescriber decides to exchange one medicine for another medicine with the same therapeutic intent.

GLO-25-1335

REFERENCES

  1. Makurvet FD. Biologics vs small molecules: Drug costs and patient access. Med Drug Discov. 2021;9:100075.
  2. European Medicines Agency. Biosimilar medicines: overview. Accessed October 2025. Available at: https://www.ema.europa.eu/en/human-regulatory/overview/biosimilar-medicines-overview.
  3. U.S. Food and Drug Administration. Biosimilars: review and approval. Accessed October 2025. Available at: https://www.fda.gov/drugs/biosimilars/review-and-approval.
  4. European Medicines Agency. Biosimilars in the EU: Information Guide for Healthcare Professionals. Published 2017. Accessed October 2025. Available at: https://www.ema.europa.eu/en/documents/leaflet/biosimilars-eu-information-guide-healthcare-professionals_en.pdf