Submission & ApprovalLast reviewed April 2026

Biosimilar(Biosimilar)

A biological product highly similar to an FDA-approved reference biologic with no clinically meaningful differences in safety, purity, and potency.

Usage Examples

The 351(k) biosimilar application relied on extensive analytical comparability plus a Phase 3 comparative efficacy trial.
Interchangeable designation required switching studies demonstrating no increased immunogenicity risk.
The biosimilar launched after the reference product's 12-year exclusivity expired.

What is Biosimilar?

A biosimilar is a biological product licensed under section 351(k) of the Public Health Service Act, established through the Biologics Price Competition and Innovation Act (BPCIA) of 2009. A biosimilar must be highly similar to its reference biologic despite minor differences in clinically inactive components and demonstrate no clinically meaningful differences in safety, purity, and potency.

The 351(k) pathway is conceptually analogous to 505(j) ANDAs for small-molecule generics but scientifically distinct: biologic complexity makes demonstrating sameness impossible, so "highly similar" is the operative standard. Biosimilar development typically includes extensive analytical characterization, nonclinical studies, and comparative clinical studies (pharmacokinetics, pharmacodynamics, and immunogenicity), with clinical efficacy studies often required in sensitive populations.

Biosimilars may be designated interchangeable — a higher standard requiring demonstration that switching between the biosimilar and reference product does not increase risk. Interchangeable biosimilars can be substituted at the pharmacy level under state law, similar to AB-rated generics. All biosimilars and interchangeable biologics appear in the Purple Book.

Regulatory Context

This term appears most often in submission & approval workflows where submission quality, regulatory evidence, and audit readiness depend on consistent language. It is commonly referenced alongside PHSA SECTION 351K, BPCIA.

FDAICHEMA

When This Matters

The 351(k) biosimilar application relied on extensive analytical comparability plus a Phase 3 comparative efficacy trial.
Interchangeable designation required switching studies demonstrating no increased immunogenicity risk.
The biosimilar launched after the reference product's 12-year exclusivity expired.

Common Mistakes

Treating submission readiness as a formatting-only check without lifecycle validation.
Using outdated guidance references across modules and summaries.
Missing cross-functional review between RA, CMC, and quality before submission.

Related Regulations

PHSA SECTION 351KBPCIA

Frequently Asked Questions

Generics demonstrate sameness to the RLD on active ingredient, strength, dosage form, and bioequivalence — made possible by well-characterized small-molecule chemistry. Biosimilars cannot demonstrate sameness because biological complexity precludes identical manufacture; instead they demonstrate "high similarity" through extensive analytical, nonclinical, and comparative clinical evidence.

Only interchangeable biosimilars can be substituted at the pharmacy level without prescriber intervention (and only where state law permits). Non-interchangeable biosimilars require a prescriber to specifically order the biosimilar. All biosimilars can be prescribed as alternatives to the reference product.

Biosimilar development typically takes 6-10 years and costs $100-300M — substantially less than a novel biologic ($800M-$2B over 10-15 years) but far more than a small-molecule generic. The analytical, nonclinical, and comparative clinical program is the major cost driver.