As the name implies, a biosimilar drug is different but highly similar to an original, FDA-approved biologic drug. The original drug is called a parent biologic drug or reference biologic.

See Biologics: Basic Facts for Patients

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For the FDA to approve a biosimilar, the parent and biosimilar drug must:

  • Be administered the same way (e.g. injection) at the same dose and strength
  • Work the same way in the body--pharmacists call this the same mechanism of action
  • Be shown to have the same safety and efficacy in patients

To be approved as a biosimilar, clinical research must show no significant differences in efficacy and safety between the biosimilar and the parent biologic. In other words, individual patients may have different reactions to the two drugs, but overall, a large group of patients taking either drug will experience the same or similar symptom reduction and side effects.

Biosimilars are not generics
A biosimilar can have minor differences compared to its parent biologic—for example, it may contain material that is a byproduct of production that does not change the drug’s effect. In contrast, generic pharmaceutical drugs are considered essentially the same as their brand-name parents (for example Zocor and its generic simvastatin). For this reason biosimilars are not considered generic versions of biologics.


Example: Humira and Amjevita

Humira is the brand name for adalimumab, a biologic approved by the FDA in 2002. In 2016, the FDA approved a biosimilar for Humira called Amjevita. Amjevita is expected to be available by prescription before the end of 2018.

Prescriptions for “Humira” or “adalimumab” will get filled with Humira. Prescriptions for Amjevita should specify “Amjevita” or “adalimumab-atto” (those four letters after the hyphen indicate the drug is a biosimilar).

Other examples of biosimilars include Erelzi (etanercept-szzs), which is highly similar to Enbrel (etanercept), and Inflectra (infliximab-dyyb), which is highly similar to Infliximab (infliximab) which is FDA approved to treat moderate to severely active rheumatoid arthritis in combination with methotrexate; active ankylosing spondylitis; active psoriatic arthritis; and chronic severe plaque psoriasis.


Interchangeable Biosimilars

Biosimilars can be approved by the FDA as “interchangeable” with their parent biologics. To be approved as interchangeable, research must show that the biosimilar drug produces the exact same results in an individual patient—meaning that a person can take either drug and expect the same symptom reduction and same side effects. To date, no biosimilars have been approved as interchangeable.

See Risks and Side Effects of Biologics

If the FDA ever approves a biosimilar drug as interchangeable, then a pharmacist will be able to fill a prescription for the parent biologic drug with the interchangeable product without getting permission from the patient’s doctor.

Rules about exactly how pharmacists can dispense biosimilar products can be different from state to state. Patients can ask their doctors or pharmacists questions regarding their prescriptions at any time.

Dr. Kathee de Falla is a licensed and certified pharmacist. She has more than a decade of experience providing medical advice and supplying prescription medications in a retail setting. Dr. de Falla spent several years developing drugs at Abbott Laboratories, a pharmaceutical company where she holds a patent for a drug formulation.