Biosimilars: A Guide for Pharmacists

Biosimilars are products that are highly similar to FDA-approved biologic medications, which are known as reference products. Biosimilars are produced from the same types of living sources (eg, bacteria, yeast), and have the same strength, dosage, route of administration, and expected therapeutic benefits and adverse effects as reference products. Therefore, no clinically meaningful differences are anticipated.¹ The FDA approved the first biosimilar on the US market, filgrastim-sndz (Zarxio; Sandoz), in 2015; since then, an additional 88 products have been approved, for a total of 89.²

Biosimilars enhance patient access to otherwise expensive treatments as they are priced on average 50% lower than the reference product at the time of the biosimilar launch.³ Biosimilar use has resulted in $56 billion in savings for patients and the health care system since 2015. Despite the cost savings, biosimilars make up less than 20% of the biologic market and their adoption has lagged.³ This is due to a variety of factors including pharmacy benefit manager formulary decisions, regulatory hurdles, and hesitancy among both patients and providers.^3,4 Nonetheless, the goal of bringing lower-cost biosimilars to the US market persists and pharmacists are integral in educating prescribers and patients on the benefits these agents provide. Therefore, it is important that pharmacists have a clear understanding of biosimilars with respect to their approval process as well as other practical and clinical implications for their use.

Regulatory Approval of Biosimilars

The FDA approval process for a biosimilar product was created through the Biologics Price Competition and Innovation Act of 2009.⁵ The process differs from that used to approve a typical, small molecule, generic drug. The manufacturer of a generic drug product must ensure that the active ingredient is identical to the reference brand drug; however, this is not feasible for biosimilars. Biologics are complex, cell-derived products that cannot be replicated identically because of the inherent variability in proteins produced during the manufacturing process. Thus, a manufacturer of a proposed biosimilar product is expected to demonstrate “high similarity” to the reference product. Since the safety and effectiveness of the reference product has already been established, biosimilar manufacturers can rely on existing clinical evidence rather than conducting costly, extensive trials that may take years to complete.⁵

The strategy used to establish biosimilarity is rigorous but not standardized. Instead, the FDA reviews various types of data supplied by the manufacturer of a proposed biosimilar product through the 351(k) pathway. This pathway is an abbreviated form of the Biologics License Application, the formal submission to the FDA through which a manufacturer requests permission to introduce a biological product on the market.

A “totality-of-the-evidence” approach is ultimately used to determine biosimilarity.⁶ Comparative analytical assessments are the cornerstone of biosimilar product development.⁶ Numerous physicochemical and functional assays are conducted by the manufacturer to ascertain the similarity between the proposed biosimilar and the reference product and to evaluate the potential impact of any differences on the biosimilar’s activity, pharmacokinetics, pharmacodynamics, safety, efficacy, and immunogenicity. Quality attributes that are evaluated include the molecular structure (eg, amino acid sequence), bioactivity (eg, target binding), and purity (eg, protein concentration).⁶

The results of these comparative analytical assessments provide the scientific basis for the subsequent studies conducted by the manufacturer to demonstrate biosimilarity, which may include animal studies to evaluate the toxicology and pharmacology of the agent, and clinical studies to establish similar exposure, efficacy, and safety.⁶ The clinical studies could include pharmacology studies evaluating pharmacokinetics, pharmacodynamics, and immunogenicity, and comparative efficacy studies if uncertainty remains regarding whether the biosimilar product has no clinically meaningful differences from the reference product.^5,7

Additional data are also required for any biosimilar that is being proposed as an interchangeable. Interchangeability is important in clinical practice, as only interchangeable products may be substituted for the reference product at the pharmacy level without the intervention of the prescriber. To establish interchangeability, a manufacturer must provide evidence that switching between a biosimilar and reference product would not have a substantial clinical impact on safety and effectiveness. This has been accomplished by way of a switching study, in which patients alternate between agents for a given period.⁵

Notably, in an effort to accelerate biosimilar approval, the FDA issued draft guidance in the fall of 2025 to simplify the development process, outlining circumstances where comparative clinical efficacy studies may not be necessary.⁸ This guidance is based on newer evidence suggesting that a comparative analytical assessment is generally more sensitive than a comparative efficacy study in detecting whether there are differences between 2 products that may limit biosimilarity.⁹ Through a separate initiative, the FDA is also aiming to streamline the approval of interchangeables, issuing draft guidance that generally no longer recommends costly switching studies.^9,10

Practical Considerations for Pharmacists

Naming Conventions and Product Labeling

In 2017, the FDA changed the nonproprietary naming of biologic products such that most agents, including original reference products, biosimilars, and interchangeables, must use the same core name that identifies the drug substance and conveys information about the drug’s pharmacologic properties, followed by a unique four-letter suffix. The suffix (eg, “-atto”, “-adbm”) has no significant meaning on its own; rather, it supports pharmacovigilance particularly in situations when other identifiers, such as National Drug Codes, may not be available. The suffixes essentially allow health care providers to differentiate between related biological products.^11,12

The prescribing information (PI) for a biosimilar includes a statement identifying the reference product to which high similarity was established; information concerning interchangeability is not included.¹¹ The labeling will also include relevant information from the reference product labeling to ensure safe and effective use of the medication. However, certain sections of the PI may be different. For example, a biosimilar may be approved for fewer indications or dosing regimens. A biosimilar may also have different preparation, administration, and/or storage instructions. This underscores the importance of reviewing the labeling of each product carefully prior to dispensing.¹¹

Pharmacy-Level Substitutions

Multiple biosimilar and interchangeable products may exist for a single referenceproduct. To illustrate this point, consider the reference product adalimumab (Humira; AbbVie), a tumor necrosis factor blocker indicated for several autoimmune conditions. There are 2 products approved as biosimilars to Humira: adalimumab-aacf (Idacio; Fresenius Kabi) and adalimumab-aqvh (Yusimry; Coherus BioSciences). However, there are 8 products also designated as interchangeable (adalimumab-afzb [Abrilada; Pfizer], adalimumab-atto [Amjevita; Amgen],adalimumab-adbm [Cyltezo; Boehringer Ingelheim], adalimumab-bwwd [Hadlima; Samsung Bioepis], adalimumab-fkjp [Hulio; Biocon Biologics], adalimumab-adaz [Hyrimoz; Sandoz], adalimumab-ryvk [Simlandi; Alvotech], and adalimumab-aaty [Yuflyma; Celltrion]).¹³ The ever-growing number of biological products necessitates that pharmacists knowwheretolocateinformation concerning biosimilarity and interchangeability.

Much like the FDA’s Orange Book, which lists all FDA-approved prescription and OTC non-biological drugs and denotes therapeutically equivalent generic products, the Purple Book contains a wealth of information regarding FDA-approved biologics. The Purple Book database can be searched by entering either the proprietary name or the nonproprietary name of a biologic into either the simple search or the advanced search field.¹⁴ Simple search results list all the biological products that share the same core name; agents that are biosimilar to or interchangeable with a reference product are designated with a matching color. Links to the PI and additional information (eg, approval date, dosage form, route, strength, manufacturer, patent information) are also noted. The advanced search allows one to view and sort all available data in a table format and to download results, a feature that may be useful to manufacturers and researchers.¹⁴

In addition to identifying which products are designated as interchangeable and therefore eligible for substitution, pharmacists must comply with state-specific laws governing pharmacy-level substitutions, which vary across jurisdictions. For instance, in New York, pharmacists receiving a prescription for a proprietary reference product must substitute it with an interchangeable product, provided that the prescription does not preclude substitution, and the prescriber is notified of the name and manufacturer of the substituted product within 5 days of dispensing.¹⁵ However, in Virginia for example, a pharmacist may substitute with an interchangeable product, and while the current statute requires that the patient be informed of the substitution, it does not require pharmacists to notify the prescriber of the change.¹⁶ Legal questions concerning dispensing should be addressed with state boards of pharmacy.

The Role of the Pharmacist in Promoting Biosimilar Adoption

Pharmacists play a critical role in promoting the adoption of biosimilars by addressing the apprehension and/or lack of knowledge that prescribers and patients may have regarding safety, efficacy, and quality. On a personal level, pharmacists should provide prescribers with information to aid in decision-making and reduce hesitancy, while also educating patients on the similarities and differences between biosimilars and reference products.The FDA website includes several multimedia education materials (fact sheets, videos, and infographics) in multiple languages for both patients and health care professionals that may be used by pharmacists in this endeavor.¹⁷

Patients may also be directed to the websites of medical organizations, many of which provide information about biosimilars. The National Psoriasis Foundation’s website, for example, contains links to podcasts, webinars, downloadable PDFs, and additional resources.¹⁸

On a larger scale, pharmacists can impact biosimilar adoption within institutions by advocating for their inclusion onformularies, leading therapeutic interchange initiatives, and conducting quality improvement strategies (eg, medication use evaluations) to evaluate use and patient outcomes. The continued growth of the biosimilar market, driven by several factors including patent expirations, rising chronic disease prevalence, and payer emphasis on cost-effective therapies, will further underscore the essential role of pharmacists in facilitating the appropriate integration of these therapies into patient care.¹⁹

REFERENCES

1. Overview for health care professionals. FDA. August 1, 2024. Accessed August 18, 2026. https://www.fda.gov/drugs/biosimilars/overview-health-care-professionals

2. Biosimilar product information. FDA. August 4, 2026. Accessed August 18, 2026. https://www.fda.gov/drugs/biosimilars/biosimilar-product-information

3. Fact sheet: bringing lower-cost biosimilar drugs to American patients. US Department of Health and Human Services. October 29, 2025. Accessed August 18, 2026. https://www.hhs.gov/press-room/fact-sheet-bringing-lower-cost-biosimilar-drugs-to-american-patients.html

4. Rome BN, Bhaskar A, Kesselheim AS. Biosimilar interchangeability and substitution in the US: what comes next? Am J Manag Care. 2026;32(4):198-201. doi:10.37765/ajmc.2026.89826

5. Review and approval. FDA. December 13, 2022. Accessed August 18, 2026. https://www.fda.gov/drugs/biosimilars/review-and-approval

6. Biosimilars info sheet: comparative clinical assessment and product quality. FDA. Accessed August 18, 2026. https://www.fda.gov/media/182186/download?attachment

7. Biosimilars info sheet: comparative clinical studies. FDA. Accessed August 18, 2026. https://www.fda.gov/media/154916/download?attachment

8. Scientific considerations in demonstrating biosimilarity to a reference product: updated recommendations for assessing the need for comparative efficacy studies. U Department of Health and Human Services. October 2025. Accessed August 18, 2026. https://www.fda.gov/media/189366/download

9. FDA moves to accelerate biosimilar development and lower drug costs. News release. FDA. October 29, 2025. Accessed August 18, 2026. https://www.fda.gov/news-events/press-announcements/fda-moves-accelerate-biosimilar-development-and-lower-drug-costs

10. Considerations in demonstrating interchangeability with a reference product: update; draft guidance for industry. FDA. June 21, 2024. Accessed August 18, 2026. https://www.regulations.gov/document/FDA-2017-D-0154-0065

11. Biosimilars info sheet: labeling for biosimilar and interchangeable biosimilar products. FDA. Accessed August 18, 2026. https://www.fda.gov/media/182188/download?attachment

12. Nonproprietary naming of biological products guidance for industry. FDA. January 2017. Accessed August 18, 2026. https://www.fda.gov/regulatory-information/search-fda-guidance-documents/nonproprietary-naming-biological-products-guidance-industry

13. Humira. Purple Book: Database of Licensed Biological Products. FDA. Accessed August 18, 2026. https://purplebooksearch.fda.gov/index.cfm?event=simplesearch&proprietary=Humira&proper=adalimumab

14. Purple Book: Database of Licensed Biological Products. FDA. Accessed August 18, 2026. https://purplebooksearch.fda.gov/userguide

15. Section 6816-A. NY Senate. Accessed August 18, 2026. https://www.nysenate.gov/legislation/laws/EDN/6816-A

16. § 54.1-3408.04. Dispensing of interchangeable biosimilars permitted. Code of Virginia. Accessed August 18, 2026. https://law.lis.virginia.gov/vacode/title54.1/chapter34/section54.1-3408.04/

17. Multimedia education materials | biosimilars. FDA. Updated November 8, 2024. Accessed August 18, 2026. https://www.fda.gov/drugs/biosimilars/multimedia-education-materials-biosimilars#For%20Health%20Care%20ProvidersDD

18. Biosimilars. National Psoriasis Foundation. Accessed August 18, 2026. https://www.psoriasis.org/biosimilars/

19. Biosimilars market to reach USD 72.29 billion by 2035, driven by expanding biologics demand and patent expirations. News release. BioSpace. May 13, 2026. Accessed August 18, 2026. https://www.biospace.com/press-releases/biosimilars-market-to-reach-usd-72-29-billion-by-2035-driven-by-expanding-biologics-demand-and-patent-expirations