A biosimilar is a biological product that is similar to a reference biologic (usually the originally approved product) and for which there are no clinically meaningful differences in terms of safety, purity, and potency. The most recent biosimilar approval was Starjemza (ustekinumab-hmny), an interchangeable biosimilar to Stelara, on May 22, 2025.

An example of a biosimilar is Amjevita (adalimumab-atto), the first biosimilar approved for Humira (adalimumab) in 2016. In this case, Humira is the reference (original) product that fulfilled the adalimumab clinical studies and was approved by the FDA. Biosimilars are not always approved for the same uses (indications) as the reference biologic.

Biosimilars are meant to be more affordable than the reference product. They are expected to help the U.S. healthcare system and consumers save money, but biosimilar products are still very expensive and unaffordable for most patients without prescription insurance. An interchangeable biosimilar product may be substituted by a pharmacist without the intervention of the prescriber, which may lead to cost savings.

According to the RAND Corporation, biosimilars could help save the U.S. health care system close to $54 billion on biologics spending through 2026.

How many biosimilars are there?

As of April 17, 2025, there are 75 biosimilars, including at least 16 that are designated as interchangeable products and approved by the U.S. Food and Drug Administration (FDA).

The most recent biosimilar approvals in 2025 include:

• Starjemza (ustekinumab-hmny), an interchangeable biosimilar to Stelara (May 22, 2025)
• Jobevne (bevacizumab-nwgd), a biosimilar to Avastin (April 9, 2025)
• Bomyntra (denosumab-bnht), a biosimilar to Xgeva (March 25, 2025)
• Conexxence (denosumab-bnht), biosimilar to Prolia (March 25, 2025)
• Omlyclo (omalizumab-igec), an interchangeable biosimilar to Xolair (March 7, 2025)
• Osenvelt (denosumab-bmwo), a biosimilar to Xgeva (Feb. 28, 2025)
• Stoboclo (denosumab-bmwo), a biosimilar to Prolia (Feb 28, 2025)
• Merilog (insulin aspart-szjj), a biosimilar to NovoLog (Feb 14, 2025)
• Xbryk (denosumab-dssb), a biosimilar to Xgeva (Feb 13, 2025)
• Ospomyv (denosumab-dssb) - a biosimilar to Prolia (February 13, 2025)
• Avtozma (tocilizumab-anoh) a biosimilar to Actemra (Jan 24, 2025)

An interchangeable biosimilar product may be substituted by a pharmacist without the intervention of the prescriber, meaning a more affordable biosimilar may be accessible for the patient and the healthcare system.

A healthcare provider also can prescribe an interchangeable product similar to how they would prescribe a biosimilar or a reference product. Pharmacy laws for biosimilar prescribing may vary by state.

See What biosimilars have been approved in the U.S? to review a full listing of all biosimilars and their interchangeability status.

What is a biologic?

If a biosimilar is a biologic, then what is a biologic? Biological products can include a wide range of products including:

• vaccines
• blood components
• gene therapy
• tissues
• proteins, like monoclonal antibodies and cell signaling proteins.

Unlike most chemically-derived small-molecule drugs, biological products are generally derived from a living organism, such as humans, animals, microorganisms or yeast. Clinically, they are used to treat patients with cancer, kidney diseases and autoimmune diseases, such as rheumatoid arthritis and Crohn's disease.

For example, Enbrel (etanercept) or Humira (adalimumab) are referred to as “large-molecule” drugs because they are larger and more complex in structure than small-molecule drugs (like ibuprofen).

Biologic products are very expensive, often in the tens-of-thousands of dollars per year, due to costs linked to complicated development and manufacturing. Patients usually have access to these medications through a specialty pharmacy.

Are biosimilars the same as a generic?

A biosimilar is not considered a “generic” in the same way that a traditional, small molecule drug (for example: ibuprofen or acetaminophen) is determined to be a generic. Biosimilars are "similar" because they are biologics that do not have to be exact copies of the active ingredient, as with small-molecule drug generics.

In 2010, the U.S. signed into law an abbreviated approval pathway for biologics to encourage production, create competition, increase treatment options and reduce healthcare costs. Under the new law, a biological product may be demonstrated to be “biosimilar” if data show that the product is “highly similar” to an already-approved biological product.

The law, known as the Biologics Price Competition and Innovation Act of 2009 (BPCI Act), aligns with the FDA’s long standing-policy of permitting appropriate reliance on drug science that has already been established, thereby saving time, resources and unnecessary duplication of animal testing or human clinical trials.

How are biosimilars named?

In January 2017 the FDA issued a guidance on naming conventions for biosimilars. According to the guidance the nonproprietary name designated "will be a proper name that is a combination of the core name and a distinguishing suffix that is devoid of meaning and composed of four lowercase letters."

In the current naming convention, the FDA has designated guidelines for approved biosimilar nonproprietary names that incorporate four lowercase letters (a suffix).

FDA has stated drug companies can propose up to 10 suffixes for each new biosimilar.
Currently, the licensed biosimilars have gained the unique 4-letter suffix, but the older reference product may not have a suffix, for example; for example: adalimumab (Humira).

Some older biosimilars are linked with the manufacturer (filgrastim-'sndz' for Sandoz), and some random (infliximab-dyyb). Going forward they will be random, have no meaning and not linked with the manufacturer's name.

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Can pharmacists automatically substitute a biosimilar for a brand name biologic?

Yes, but ONLY for FDA-approved biological products specifically designated as interchangeable, as found in The Purple Book database. According to the FDA, automatic substitution by the pharmacist can happen once a product is deemed interchangeable.

If the product has been determined to be interchangeable, then it is "biosimilar" to the reference product AND will produce the same clinical result as the reference product in any given patient. Interchangeable also means the original biologic and the new biosimilar can be switched back and forth in a patient without a risk of diminished safety or efficacy.

Biosimilars can also be dispensed by a pharmacist in place of another biological product if a physician or other healthcare professional specifically prescribes the biosimilar product by name.

Which interchangeable biosimilars are approved in the U.S.?

Reference products and their interchangeable biosimilars approved by the FDA (Purple Book) include:

Interchangeable for Soliris (eculizumab):

• Bkemv (eculizumab-aeeb)

Interchangeable for Eylea (aflibercept):

• Opuviz (aflibercept-yszy)
• Yesafili (aflibercept-jbvf)

Interchangeable for Humira (adalimumab):

• Abrilada (adalimumab-afzb)
• Amjevita (adalimumab-atto) - certain presentations
• Cyltezo (adalimumab-adbm) - certain presentations
• Hadlima (adalimumab-bwwd)
• Hulio (adalimumab-fkjp)
• Hyrimoz (adalimumab-adaz) - certain presentations
• Simlandi (adalimumab-ryvk)
• Yuflyma (adalimumab-aaty)

Interchangeable for Lantus (insulin glargine):

• Semglee (insulin glargine-yfgn)
• Rezvoglar (insulin glargine-aglr)

Interchangeable for Lucentis (ranibizumab):

• Cimerli (ranibizumab-eqrn)
• Byooviz (ranibizumab-nuna)

Interchangeable for Prolia (denosumab)

• Jubbonti (denosumab-bbdz)

Interchangeable for Stelara (ustekinumab)

• Wezlana (ustekinumab-auub)
• Starjemza (ustekinumab-hmny)
• Yesintek (ustekinumab-kfce)
• Otulfi (ustekinumab-aauz)
• Pyzchiva (ustekinumab-ttwe)
• Selarsdi (ustekinumab-aekn)
• Wezlana (ustekinumab-auub) - certain presentations

Interchangeable for Xgeva (denosumab)

• Wyost (denosumab-bbdz)

Interchangeable for Xolair

• Omlyclo (omalizumab-igec)

This may not be a complete list of interchangeable biosimilars, as approvals occur frequently. Keep in mind that biosimilars and interchangeable products may not be approved for the same indications as the reference biologic. Always review the patient or professional information.

If you have questions, ask your pharmacist. Pharmacists will know which biological products are in stock and approved as interchangeable by the FDA. They can also check The Purple Book database to find these products.

If needed, your pharmacist can contact your prescriber to request that a prescription be written for a biosimilar.

What is the Purple Book?

The Purple Book database is the go-to resource for pharmacists and other health care providers interested in making an interchange between a reference biologic and a biosimilar. It is found online on the FDA website.

Similar to The Orange Book used to compare generic products to their brand name counterparts, The Purple Book database has been developed by the FDA to list each reference biological product and the corresponding biosimilar and interchangeable biological product.

Biosimilars designated as interchangeable will have no clinically important differences from the original product. Variation in formulation, delivery device, indications, and routes of administration may be acceptable.

Additional biosimilar product information can also be accessed on the FDA website.

References

• 9 Things to Know About Biosimilars and Interchangeable Biosimilars. 6/20/2024. U.S. Food and Drug Administration (FDA). Accessed June 3, 2025 at https://www.fda.gov/drugs/things-know-about/9-things-know-about-biosimilars-and-interchangeable-biosimilars
• Purple Book. Database of Licensed Biological Products. Accessed June 3, 2025 at https://purplebooksearch.fda.gov/
• Biosimilar and Interchangeable Biologics: More Treatment Choices. U.S. Food and Drug Administration (FDA). 8/17/2023. Accessed June 3, 2025 at https://www.fda.gov/consumers/consumer-updates/biosimilar-and-interchangeable-biologics-more-treatment-choices
• Background Information: Lists of Licensed Biological Products with Reference Product Exclusivity and Biosimilarity or Interchangeability Evaluations. U.S. Food and Drug Administration (FDA) https://www.fda.gov/Drugs/DevelopmentApprovalProcess/HowDrugsareDevelopedandApproved/ApprovalApplications/TherapeuticBiologicApplications/Biosimilars/ucm411424.htm
• Implementation of the Biologics Price Competition and Innovation Act of 2009. U.S. Food and Drug Administration (FDA). Accessed June 3, 2025 at https://www.fda.gov/Drugs/GuidanceComplianceRegulatoryInformation/ucm215089.htm
• Nonproprietary Naming of Biological Products. Guidance for Industry. U.S. Department of Health and Human Services. Food and Drug Administration. Center for Drug Evaluation and Research (CDER). Center for Biologics Evaluation and Research (CBER). January 2017. Accessed June 3, 2025.
• Pavblu [prescribing information]. Revised 8/2024. Accessed June 3, 2025 at https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/761298s000lbl.pdf

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