Biosimilars and Biobetters

Learning Objectives

By the end of this page, you should be able to:

• Define a biosimilar and explain why it cannot be an exact copy of its reference biologic
• Define a biobetter and explain how it differs in purpose from a biosimilar
• Explain why biosimilars are not called "generics" and how their regulatory pathway differs from that of small-molecule generics
• Walk through the development process for biosimilars and biobetters
• Identify the main scientific and regulatory challenges facing biosimilar/biobetter development

Quick Answer

A biosimilar is a biologic drug that is highly similar - but not identical - to an already-approved "reference" biologic, developed and marketed after the reference product's patent expires; a biobetter is a deliberately improved version of an existing biologic, with enhanced properties such as longer-lasting action or fewer side effects. Both matter for the same underlying reason: biologics are grown in living cells rather than synthesized chemically, so no two manufacturers - not even the same manufacturer producing two different batches - can create a perfectly identical molecule. Biosimilars bring competition and lower prices to expensive biologic drugs (similar to what generics do for small molecules, but through a more rigorous comparability pathway), while biobetters push existing therapeutic ideas forward with genuine clinical improvements.

What Are Biosimilars?

Definition: A biosimilar is a biologic medicine shown, through extensive comparative testing, to be highly similar to an already-approved reference biologic, with no clinically meaningful differences in safety, purity, or effectiveness.

Explanation: Because biologics are produced by living cells, exact molecular replication (as is possible with small-molecule chemical synthesis) isn't achievable. Instead, a biosimilar manufacturer runs extensive analytical, preclinical, and clinical comparability studies against the reference product to demonstrate the two are "highly similar" with no meaningful clinical difference - a fundamentally different bar than proving chemical identity.

Example: Infliximab biosimilars (marketed under various brand names) were approved as highly similar to the reference product Remicade, used for rheumatoid arthritis, psoriatic arthritis, and Crohn's disease. Adalimumab biosimilars followed a similar path relative to the reference product Humira.

Real-world example: When adalimumab biosimilars entered the US market after Humira's patent protections ended, the increased competition drove meaningful price reductions for a drug that had been one of the most expensive treatments for autoimmune disease - directly improving patient access.

Why it matters: Biosimilars extend the affordability and accessibility benefits that generics brought to small-molecule drugs into the biologics space, which is otherwise dominated by very high-cost treatments.

Common misunderstanding: Students frequently call biosimilars "biologic generics." This is inaccurate: generics must be chemically identical to the reference drug, while biosimilars are only required to be "highly similar" with no clinically meaningful difference - a distinct, more involved regulatory standard because perfect replication of a living-cell product isn't scientifically achievable.

What Are Biobetters?

Definition: A biobetter is a new biologic, therapeutically related to an existing approved biologic, engineered to have improved clinical or pharmacological properties compared to the original.

Explanation: Unlike a biosimilar (which must closely match its reference product), a biobetter is deliberately different and better in some specific way - longer half-life (fewer doses needed), improved formulation, better manufacturing consistency, or reduced immunogenicity. Because it's a genuinely new molecule, it requires its own full clinical development program and patent protection, not a comparability pathway.

Example: Long-acting insulin analogs (such as insulin glargine and insulin degludec) are biobetters relative to original recombinant human insulin - they're engineered to release more slowly, reducing the number of daily injections needed.

Real-world example: Pegylated versions of existing protein drugs (attaching a polyethylene glycol molecule to the protein) often qualify as biobetters, since PEGylation extends the drug's time in the bloodstream, allowing less frequent dosing while retaining or improving therapeutic effect.

Why it matters: Biobetters represent genuine scientific improvement over first-generation biologics, often significantly improving patient convenience and adherence (e.g., a once-weekly injection instead of daily).

Common misunderstanding: Students sometimes think a biobetter can be approved through the same abbreviated pathway as a biosimilar. It cannot - because a biobetter is a distinct new molecule, not a copy of the reference product, it must go through the full, standard clinical development and approval pathway (like any new biologic), not the streamlined biosimilar comparability pathway.

Development Process

The development process for both biosimilars and biobetters shares common elements but differs in scope:

1. Research and Development - Identify target molecules/pathways; for biosimilars, this means characterizing the reference product in extreme analytical detail; for biobetters, this means designing a deliberate modification (e.g., altered half-life, reduced immunogenicity).
2. Manufacturing Scale-up - Optimize production processes and ensure batch-to-batch consistency, which is especially demanding for biologics.
3. Clinical Trials - Biosimilars typically run smaller, focused comparability trials (demonstrating equivalence to the reference product); biobetters require the full Phase 1-3 program a brand-new biologic would need, since they aren't claiming equivalence but genuine improvement.
4. Regulatory Approval - Biosimilars use an abbreviated regulatory pathway (e.g., the 351(k) pathway in the US, or the EMA's biosimilar pathway) requiring extensive comparability data rather than fully independent trials; biobetters are approved via the standard BLA pathway like any new biologic.
5. Post-Marketing Surveillance - Ongoing monitoring for long-term safety, effectiveness, and (for biosimilars) interchangeability with the reference product in real-world use.

Visual Learning

Key Terms

Term	Definition
Reference biologic	The original, already-approved biologic that a biosimilar or biobetter is compared/related to
Biosimilar	A biologic highly similar to a reference product, with no clinically meaningful difference, approved via an abbreviated comparability pathway
Biobetter	A newly engineered biologic with genuinely improved properties over an existing biologic, approved through the standard full development pathway
Interchangeability	A regulatory designation (used in some jurisdictions) allowing a pharmacist to substitute a biosimilar for its reference product without prescriber approval
351(k) pathway	The abbreviated US FDA regulatory pathway specifically for licensing biosimilars
PEGylation	Attaching polyethylene glycol to a protein drug to extend its half-life in the body
Comparability study	A study designed to demonstrate that a biosimilar has no clinically meaningful difference from its reference product
Immunogenicity	The tendency of a biologic to provoke an immune response in the patient, an important comparison point for biosimilars

Common Mistakes

Misconception 1: "A biosimilar is a cheaper, lower-quality knockoff of the original biologic." Why it's wrong: Biosimilars must pass extensive analytical, preclinical, and clinical comparability testing proving no clinically meaningful difference from the reference product before regulators approve them - the bar is scientific equivalence, not "close enough and cheap." Correct understanding: Biosimilars are lower-cost primarily because the manufacturer doesn't have to repeat the reference product's full, original clinical trial program from scratch - not because quality standards are relaxed.

Misconception 2: "Biosimilars and generics go through the same approval process." Why it's wrong: Generics are proven chemically identical to their reference drug and typically require only bioequivalence studies; biosimilars can never be proven identical (they're produced in different living-cell systems), so they require far more extensive comparative analytical and clinical data. Correct understanding: The biosimilar pathway (e.g., 351(k) in the US) is a distinct, more data-intensive regulatory route reflecting the inherent manufacturing variability of biologics.

Misconception 3: "A biobetter can be swapped in for its related biologic without new trials, the same way a biosimilar can use a comparability pathway." Why it's wrong: A biobetter is a genuinely new molecule making a claim of improvement, not equivalence, so it must be independently proven safe and effective through the full standard drug development pathway. Correct understanding: Only biosimilars use the abbreviated comparability approach; biobetters, because they're new and different by design, go through the same rigorous approval process as any novel biologic.

Comparison and Connections

Feature	Generic (small molecule)	Biosimilar	Biobetter
Relationship to original	Chemically identical	Highly similar, not identical	Deliberately different/improved
Regulatory pathway	Abbreviated (bioequivalence)	Abbreviated (comparability, e.g., 351(k))	Full standard pathway (like new biologic)
Clinical trial burden	Minimal (bioequivalence studies)	Reduced but still substantial (comparability studies)	Full Phase 1-3 program
Goal	Lower cost, same molecule	Lower cost, equivalent effect	Improved efficacy, convenience, or safety
Example	Generic ibuprofen	Biosimilar adalimumab	Long-acting insulin analog

Practice Questions

Recall

1. Define a biosimilar and a biobetter in one sentence each. Answer guidance: A biosimilar is a biologic highly similar to an approved reference product with no clinically meaningful difference; a biobetter is a newly engineered biologic with genuinely improved properties over an existing one.
2. Name the abbreviated US regulatory pathway used specifically for biosimilars. Answer guidance: The 351(k) pathway.

Understanding

3. Explain why a biosimilar can never be proven "identical" to its reference biologic the way a generic can be proven identical to its reference small molecule. Answer guidance: Biologics are produced in living cells, which introduces natural, unavoidable batch-to-batch and process-related variability, so no two manufacturing processes (even the same company's own batches) yield a perfectly identical molecule - only "highly similar with no clinically meaningful difference" is achievable and required.
4. Why does a biobetter require full clinical trials while a biosimilar can use a comparability pathway? Answer guidance: A biosimilar is claiming equivalence to an already-proven-safe-and-effective reference product, so it only needs to demonstrate that similarity; a biobetter is a new molecule making a claim of improvement rather than equivalence, so its safety and efficacy must be independently established from scratch.

Application

5. A pharmaceutical company wants to create a version of an existing insulin product that requires only one injection per week instead of daily. Would this be classified as a biosimilar or a biobetter, and why? Answer guidance: A biobetter, because the company is deliberately engineering a genuine improvement (extended duration of action, e.g., through structural modification or PEGylation) rather than trying to replicate the original product as closely as possible.
6. A country's health system wants to reduce the cost of an expensive autoimmune disease biologic after its patent expires without waiting for a brand-new drug to be developed. What option from this page directly addresses this, and what regulatory evidence would be required? Answer guidance: Approving a biosimilar of the reference biologic, which would require extensive analytical, preclinical, and comparability clinical trial data proving no clinically meaningful difference from the original before it can be marketed.

Analysis

7. Compare the business incentives behind developing a biosimilar versus a biobetter, and explain how the differing regulatory pathways shape those incentives. Answer guidance: Biosimilar development is incentivized by capturing market share in an already-proven, patent-expired drug category with lower R&D and trial costs (thanks to the abbreviated comparability pathway), favoring speed-to-market and cost competition; biobetter development requires the full trial investment of a new biologic, so it's incentivized by the ability to patent a genuinely new, differentiated product and potentially command premium pricing based on improved patient outcomes or convenience - the regulatory pathway differences directly reflect and reinforce these different business strategies.
8. A biosimilar shows a slightly different immunogenicity profile from its reference product during comparability trials, even though its core structure is highly similar. What does this reveal about the "highly similar, not identical" standard, and how might regulators respond? Answer guidance: It reveals that even minor manufacturing or formulation differences inherent to living-cell production can produce clinically relevant differences (like immune response) despite overall structural similarity, showing that "highly similar" doesn't guarantee zero clinical difference in every dimension; regulators would likely require additional immunogenicity data, more detailed labeling, or in some cases decline to grant an interchangeability designation until the difference is fully characterized and shown not to be clinically meaningful.

FAQ

Q1: Are biosimilars less effective than the original biologic? No - regulatory approval requires demonstrating no clinically meaningful difference in efficacy or safety compared to the reference product; biosimilars are considered therapeutically equivalent for their approved uses.

Q2: Can a pharmacist automatically substitute a biosimilar for the reference biologic, like they can with a generic? Only if the biosimilar has received an additional "interchangeability" designation from the regulator (where such a designation exists) - otherwise, a prescriber's specific choice is generally required, unlike the automatic substitution common with small-molecule generics.

Q3: Why do biosimilars cost less than the reference biologic if they aren't cheaper to make? Biosimilar developers avoid the enormous cost of the original discovery research and full-scale clinical trials the reference product's manufacturer already paid for; they only need to run comparability studies, which is significantly less expensive.

Q4: Is a biobetter always more expensive than the biologic it's based on? Typically yes, at least initially, since biobetters are patent-protected new products with their own full clinical development costs, similar to any newly approved branded biologic.

Q5: Can the same drug be developed as both a biosimilar and later improved into a biobetter? Yes - a company might first develop a biosimilar to a reference biologic, then separately develop a biobetter version of that same drug class with further engineered improvements, since these are two independent development strategies applied to the same therapeutic area.

Quick Revision

• A biosimilar is highly similar (not identical) to an approved reference biologic; a biobetter is a deliberately improved new biologic.
• Biosimilars are not "biologic generics" - generics require chemical identity; biosimilars require "no clinically meaningful difference," proven through comparability studies.
• Biosimilars use an abbreviated regulatory pathway (e.g., US 351(k)); biobetters go through the same full pathway as any new biologic.
• Interchangeability is a separate, additional regulatory designation some biosimilars can earn, allowing pharmacy-level substitution.
• Living-cell manufacturing makes perfect molecular replication of a biologic scientifically impossible - this is the core reason biosimilars exist as a distinct category from generics.
• PEGylation and structural modification for extended half-life are common biobetter strategies (e.g., long-acting insulin analogs).
• Biosimilar approval requires extensive analytical, preclinical, and comparative clinical data, but far less than the original reference product needed.
• Biobetters require full Phase 1-3 clinical trials because they claim improvement, not equivalence.
• Key challenges for both: complexity of biologic molecules, immunogenicity uncertainty, high manufacturing/trial costs, and regulatory hurdles specific to biologics.
• Biosimilars primarily drive cost savings and access; biobetters primarily drive clinical/convenience improvement.

Related Topics

Prerequisites: 1. Introduction to Pharmaceutical Biotechnology, 2. Drug Development and Biopharmaceuticals, 3. Protein and Antibody Drugs

Related Topics: 6. Regulatory Aspects

Next Topics: 6. Regulatory Aspects