Understanding Biosimilars

Biosimilar medicines are versions of biologics that are very similar to the original medicine, but not identical.1 The U.S. Food and Drug Administration (FDA) has approved five biosimilars as of May 2017.2 As more become available, they will increasingly be part of the conversation about how we ensure that everyone with a serious disease can get the treatment they need. But there are some remaining questions about how biosimilars are used in practice, which government agencies, patient advocacy groups and manufacturers are working to address.

Biologics and chemical medicines

Biologic medicines are made from living cells and are extremely complex relative to chemical medicines, like aspirin or statins.3

Biosimilars and biologics

Unlike generic versions of chemical medicines, which have a defined structure, it is impossible to make exact copies of biologics.3

So biosimilar medicines may be a little bit different from the original medicine. Can you spot the differences?

(Above are not actual molecular structures)


Biosimilars are given different names and labels from the original medicines. This helps patients and doctors know exactly what medicine the patient is receiving. The FDA requires that labels clearly state if the medicine is a biosimilar. And to make sure anyone can distinguish a biosimilar from the original, FDA gives biologics and biosimilars four-letter suffixes that are appended to the scientific name.4

FDA approval

Biosimilars have to follow a specific regulatory pathway in order to be approved by the FDA. The type of studies for biosimilars may be different than those of original medicines. They do have to be studied carefully to confirm they are “highly similar” to the original. This is a stepwise process that starts with defining and describing the structure of the original molecule and the biosimilar molecule. From there, clinical studies are performed and patients’ responses to the biosimilar medicine are assessed.5

Biosimilars that meet an even higher threshold of testing can be approved as “interchangeable,” which means they can be expected to produce the same result for any given patient as the original medicine. No interchangeable biosimilars have been approved yet.5

It’s possible for a biosimilar to be studied in one group of patients, such as those with colon cancer, and get approved by the FDA to treat a different group of patients, such as those with lung cancer. This is called “extrapolation.” But since medicines can act differently in one disease compared with another, there may be cases where it’s necessary to conduct additional studies to confirm a biosimilar works as expected in certain diseases.


Interchangeable biosimilars can be substituted by a pharmacist without consulting the doctor or patient first. This practice is widely accepted for generic medicines but is still under consideration by some state legislatures for interchangeable biosimilars.6 Here’s how it works: your doctor writes a prescription for the original medicine. You take the prescription to your local pharmacy where the pharmacist can give you a biosimilar instead, as long as it’s approved as interchangeable.

This practice can vary by state, but most states require that the patient and/or doctor be notified of a substitution.6

It's important that people taking the medicine on an ongoing basis can be switched from the original to the biosimilar, or vice versa, without any change in safety or effectiveness. Doctors can tell pharmacists not to substitute for a biosimilar by writing “Do Not Substitute” on the prescription, but patients should be aware that their medicines could be substituted and talk to their doctor if they have questions.

You can learn more about biosimilars here and here.


1 Office of the Commissioner. (2015). Biosimilars: More Treatment Options Are on the Way. U.S. Food and Drug Administration’s Consumer Updates. Retrieved from http://1.usa.gov/1CNyPIg.

2 Center for Drug Evaluation and Research (2017). List of Licensed Biological Products with (1) Reference Product Exclusivity and (2) Biosimilarity or Interchangeability Evaluations to Date. Retrieved from https://www.fda.gov/downloads/drugs/developmentapprovalprocess/howdrugsaredevelopedandapproved/approvalapplications/therapeuticbiologicapplications/biosimilars/ucm549201.pdf.

3 Dorey, E. (2014). Forces Driving the Evolution of Biologics into Biosimilars and Biobetters. The Pharmaceutical Journal: Clinical Pharmacist, 6(9). Retrieved from http://www.pharmaceutical-journal.com/news-and-analysis/features/forcesdriving-the-evolution-of-biologics-into-biosimilars-and-biobetters/20067091.article. Accessed April 28, 2017.

4 FDA Guidance for Industry (2017). Nonproprietary Naming of Biological Products. Retrieved from https://www.fda.gov/downloads/Drugs/GuidanceComplianceRegulatoryInformation/Guidances/UCM459987.pdf.

5 FDA Guidance for Industry (2015). Scientific Considerations in Demonstrating Biosimilarity to a Reference Product. Retrieved from https://www.fda.gov/downloads/drugsguidancecomplianceregulatoryinformation/guidances/ucm291128.pdf.

6 Cauchi, R. (2017). State Laws and Legislation Related to Biologic Medications and Substitution of Biosimilars. National Conference of State Legislatures (NCSL). Retrieved from http://bit.ly/1lvTIQM. Accessed May 25, 2017.

Nevada (State). Legislature. Assembly. Enacts provisions governing the dispensing of biological products and interchangeable biological products (AB245). 2017. Nevada Legislature. Retrieved from http://bit.ly/2rSjTPI.

Maryland (State.) Legislature. Assembly. Pharmacists – Substitution and Dispensing of Biological Products (SB0997). 2017. Maryland General Assembly. Retrieved from http://bit.ly/2s0zKIq.

Nebraska (State). Legislature. Senate. Provide for drug product selection for interchangeable biological products (LB481) 2017. Nebraska Unicameral Legislature. Retrieved from http://bit.ly/2qlkcye.

Minnesota (State). Legislature. House. Biological product substitution standards established, and definitions modified and added (HF 712) 2017. Minnesota State Legislature. Retrieved from http://bit.ly/2s0HV7r.

South Carolina (State). Legislature. Assembly. Drug substitutions (H3438) 2017. South Carolina Legislature. Retrieved from http://bit.ly/2qheXUm.

Kansas (State). Legislature. Senate. Kansas Pharmacy Act Amendments; Filling and Refilling Prescriptions; Biological Products (HB2055) 2017. Kansas Legislative Sessions. Retrieved from http://bit.ly/2r1k3Bf.

New Mexico (State). Legislature. House. Regulation Of Biosimilar Products (HB 260) 2017. New Mexico Legislature. Retrieved from http://bit.ly/2s0J92t.