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A biosimilar, or biosimilar drug, is a medicine that is very close in structure and function to a biologic medicine.
A biologic, or biologic drug, is a medicine made in a living system, such as yeast, bacteria, or animal cells.
Biologics used in the treatment of cancer can work in many ways. For example, they might:
Immunotherapy and some targeted therapy drugs are examples of biologics used in cancer treatment.
For some brand name biologics, one or more biosimilars are available. A biosimilar has a structure that is highly similar to, but not exactly the same, as a brand name biologic. A biosimilar behaves in much the same way, so that there are "no meaningful differences" between it and its brand name biologic. This means that the biosimilar is also considered as safe and effective as the biologic. Both come from living systems.
You've probably heard about generic drugs. A generic drug is an exact copy of a brand name drug. Generic drugs work the same way and can be used in the same ways as their brand name drugs. In other words, a generic drug is an equal substitute for its brand name drug and can be used to treat the same disease.
A biosimilar is a little like a generic version of a biologic drug, but there are important differences. For example, unlike a generic drug, a biosimilar is not an exact copy of its brand name drug.
Here are ways biosimilar and generic drugs are alike:
Here are ways biosimilar and generic drugs are different:
All of these differences are due to the way biologics (and biosimilars) are made in the lab using a natural source (a living system such as yeast, bacteria, or animal cells).
A generic drug is an exact copy of its brand name drug (that is, it has the exact same chemical makeup). This is possible because the active ingredients in drugs are made from chemicals that have a specific structure that can be copied.
However, a biologic comes from a biologic (natural) source that cannot be copied exactly. These medicines come from very complex, living systems whose environments can change. So, while a biosimilar is the same in the most important ways, it cannot be exactly the same in its structure. A biosimilar is highly similar to its brand name drug, but not an exact copy of it.
When a generic drug is approved by the FDA, it's usually automatically interchangeable with its brand name drug. There is no additional information needed by the FDA to show a generic drug is a safe and effective substitute for its brand name drug. Because its active ingredient has the exact same chemical structure, a prescription written for a brand name drug can usually be filled using a generic drug instead. So, a patient who is taking a generic drug can expect the same outcome as if they were taking its brand name drug, and can go back and forth between them (if needed) without seeing a difference.
When a biosimilar gets its initial FDA approval, it's not automatically interchangeable with its brand name biologic. While biosimilars can be used to treat a disease once they get initial approval, they need another, special FDA approval to be considered interchangeable before they can be substituted automatically for a brand name biologic. If a biosimilar is not approved as interchangeable, it needs a prescription to be written specifically for the biosimilar to be used instead of its brand name biologic.
There are strict FDA rules that need to be met for a biosimilar to be approved as interchangeable. Any biosimilar that's approved for use has been shown in data from clinical trials to be as safe and effective in treating a certain disease as its brand name biologic. The company that makes the biosimilar may decide to only submit data to the FDA for this initial approval. But if the company wants their biosimilar to be considered interchangeable (and therefore able to be automatically substituted for its brand name drug), they must submit more information from clinical trials to the FDA. You can read more about this on the FDA website.
Like other medicines, a biosimilar needs to be tested in clinical trials and approved by the FDA before it can be used to treat a disease. In clinical trials, the biosimilar is compared to its original biologic, which was developed first. The original biologic is a brand name drug that has already gone through clinical trials, has been approved, and is being used to treat a disease. Clinical trials are then needed to test if the biosimilar is as safe and effective in treating the same disease as the brand name biologic.
The clinical trials that test all drugs and biologics are thorough and strict. But the clinical trials that test a biosimilar can move along faster than the clinical trials that were required of the brand name biologic when it was being tested. During the studies on the biosimilar, testing is done to be sure it is the same as the brand name biologic in certain ways. Testing needs to show that both medicines:
The data from the studies are carefully reviewed by the FDA to be sure the biosimilar is just as safe and effective as the brand name biologic.
If a biosimilar is approved by the FDA, this means it has met the strict standards for being safe.
Learn more in Biosimilar Drug Safety.
Biologics are often very expensive because they cost a lot to study and make. And unlike the case with drugs, where generic versions can lead to increased competition and lower prices, until fairly recently there were no alternate versions of biologics.
The high cost of biologics can sometimes make it hard for a person to get them, even if they might be the best treatment for a disease. To make biologic drugs more affordable and available to more people, Congress passed the Biologics Price Competition and Innovation Act (BPCIA). This act let the FDA create a shortened approval process for biosimilars.
Some experts have estimated that biosimilars could reduce the cost of biologics over time by many billions of dollars. But this depends on how many biosimilars are approved and become available. It also depends on what types of diseases can be treated with biosimilars and how much these medicines are used.
There are many biologic medicines, such as immunotherapy drugs, now being used to treat cancer, and some have biosimilar versions available. Some biosimilars have been approved to treat certain types of cancer, and some have been approved to help manage side effects. To find out more, see the List of Biosimilars Used in Cancer Treatment.
You can also learn more about how different types of cancer are treated in Cancer A to Z and by talking to your cancer care team.
Some insurance companies will cover the cost, or part of the cost, of a biosimilar. Others might not. If a biosimilar is a treatment option for you, it's important to talk to your insurance company about coverage.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
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Last Revised: April 27, 2022
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