What Is an Interchangeable Biosimilar Drug?

In 2010, the FDA-approval pathway for biosimilar medications was created. This allowed manufacturers to develop biosimilars, which are highly similar versions of other biologic medications. One of its key goals was to bring lower-cost options to the market. More options can drive down prices through competition. 

The concept of interchangeable biosimilars was also introduced through this pathway. In 2021, the FDA approved the first two biosimilars with this designation. This is important because pharmacists can more easily substitute biologics with these lower-cost options.

Here, we’ll cover how interchangeable biosimilars are different from regular biosimilars, and which ones are available to date.

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What is a biosimilar drug?

You may be wondering what biosimilars are and why they need their own approval pathway. After all, aren’t they just another type of generic medication? Not exactly. To understand the difference, we need to first define a biologic.

Biologics are complex drugs that come from natural or living sources. This makes them difficult to copy, unlike generic drugs that are made from chemicals. Unlike brand name medications having generics, biologics have biosimilars — highly similar biologics with comparable safety and effectiveness.

What is an interchangeable biosimilar drug?

If you’ve ever been prescribed a medication, the original prescription may have been written for the brand-name product. And there’s a good chance that your pharmacist automatically switched it to a lower-cost generic version. This is usually done to help save you some money.

Similarly, this scenario is also possible with a biosimilar and its original (reference) biologic. But this concept doesn’t apply to all biosimilars. Only interchangeable biosimilars can be automatically substituted like this at the pharmacy. If a biosimilar isn’t classified as interchangeable, your healthcare provider would need to send in a prescription for the biosimilar medication specifically.

Biosimilar vs. interchangeable biosimilar drugs: What’s the difference?

Regular and interchangeable biosimilars are slightly different. That’s because interchangeable biosimilars go a step further during their approval process. They have extra data that shows people can switch between the biosimilar and its reference biologic without issues.

This doesn’t mean that interchangeable biosimilars are better than regular biosimilars. All biologics and biosimilars have to meet strict quality and safety regulations. But this extra data allows them to be substituted more easily at the pharmacy. This means your pharmacist may not need to contact your healthcare provider to make the switch.

So, why is this a big deal? Because biologics can be very expensive. And biosimilars typically cost less than their reference product. Plus, they provide the same treatment benefits.

Keep in mind: Your healthcare provider can prescribe a biosimilar at any time. But the interchangeable status enables pharmacists to make the switch if they don’t. However, the ability to do this can vary based on state law. It also depends if your healthcare provider allows substitutions. Check with your pharmacist about the specific requirements in your state.

Are all biosimilars interchangeable?

No. In fact, most biosimilars available today are not interchangeable. But we could see more interchangeable biosimilars approved in the near future.

What interchangeable biosimilar drugs are currently FDA approved?

The FDA approved the first biosimilar in 2015. But they’ve only started approving interchangeable biosimilars in 2021. To date, four have been approved, as detailed in the table below.

Semglee was the first FDA-approved interchangeable biosimilar. It’s a long-acting insulin used to help control blood sugar levels in people living with diabetes. Semglee’s reference product is Lantus.

Cyltezo was the second FDA-approved interchangeable biosimilar. It’s a monoclonal antibody medication used to treat several different autoimmune disorders. Cyltezo’s reference product is Humira. Cyltezo won’t be available in the U.S. until at least July 2023.

Cimerli was the first FDA-approved interchangeable biosimilar to Lucentis, an injection used to treat different eye conditions. It was launched in the U.S. in October 2022.

Rezvoglar, another long-acting insulin, is the fourth and most recently approved interchangeable biosimilar. It became the second Lantus biosimilar in 2021. About 1 year later, it was approved as an interchangeable biosimilar.

Several other biosimilar medications are pursuing interchangeable status. Some are already approved as traditional biosimilars, while some are still going through initial studies. Examples include:

Ways to save on interchangeable biosimilar drugs

As mentioned above, cost can be a barrier to accessing biologic drugs. They’re also often used to treat serious and sometimes life-threatening health conditions. So being able to afford treatment is incredibly important. 

So, how much do biosimilars cost? They tend to be about 10% to 37% less expensive than their reference biologic. They’ve also opened the door for more competition to help drive prices down. And interchangeable biosimilars may make it easier for your pharmacist to help you save money.

Semglee is available as both a brand-name and unbranded product. If you qualify, you could pay as little as $0 for your prescription using a copay savings card through the manufacturer. And with GoodRx, unbranded Semglee’s price is as low as $31.29 at certain pharmacies.

Cimerli injections are given by your healthcare provider. In addition to the medication cost, they may charge you an additional fee for administering the injection. If you’re eligible, you could pay as little as $0 for Cimerli with a copay savings program through the manufacturer. The program may also cover a portion of the administration fee.

Cyltezo and Rezvoglar haven’t launched yet in the U.S. But manufacturer copay savings cards and patient assistance programs may be available once they do.

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Written by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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