Biosimilars: What is Interchangeability, Reference Product, and Why You Should Care

Recently, I had a conversation with a small group of patients from the #PatientsRisingFam about biosimilars. It was a good chat, but we all agreed there are certain terms that, if not understood, make biologics confusing quickly. So here is a brief explanation of biosimilar interchangeability and some terms needed to understand it.

If you want to take the long road, visit out Biologics & Biosimilars module on Patients Rising University

What is a reference product?

BIOSIMILARS are created to perform ‘similarly’ to a BIOLOGIC that is already FDA approved. When a BIOSIMILAR is being developed to perform without clinically meaningful differences to an existing FDA-approved BIOLOGIC product, that BIOLOGIC product is referred to as the REFERENCE PRODUCT.

A BIOLOGIC can only be called a REFERENCE PRODUCT when there is a BIOSIMILAR that ‘refers’ to it.

It’s the industry way of saying “this BIOSIMILAR is similar to this particular BIOLOGIC”.

what is biosimilar interchangeability?

When a BIOSIMILAR can show that it “produces the same clinical result” in any patient it is given to, it may qualify to be INTERCHANGEABLE with it’s REFERENCE PRODUCT. To obtain BIOSIMILAR INTERCHANGEABILITY, the biosimilar has to meet additional requirements with the FDA.

Biosimilar Interchangeability allows a pharmacist to substitute that interchangeable biosimilar for it’s REFERENCE PRODUCT when prescribed. This can be done without permission from the prescribing physician.

Aren’t all biosimilars interchangeable?

No. Remember, a biosimilar is only ‘similar’ to the biologic that is its reference product. Similarity means there is no “clinically meaningful difference” between the biosimilar and the reference product. Interchangeability is a higher standard than that.

why you should care

Let’s say your doctor writes a prescription for a biologic. The pharmacy must fill that prescription as it is written even if there is a biosimilar for that reference product. However, if there is an “interchangeable biosimilar” for that reference product then the pharmacist can fill the prescription with the biologic or with the interchangeable biosimilar without consulting your physician.

This is possible because not only has the FDA found no clinically meaningful difference between that biosimilar and the biologic it references, but that the same can be said about anyone who might receive the drug. That’s the higher standard.


Q: So, is an INTERCHANGEABLE BIOSIMILAR safer or more effective than the REFERENCE BIOLOGIC?

A: No, they are essentially the same. In fact, they are more than “similar” they are “interchangeable”.

Q: Why would I want my pharmacist to “interchange” my medications?

A: One main reason is that the INTERCHANGEABLE BIOSIMILAR is probably much cheaper than the REFERENCE BIOLOGIC.

jim sliney jr

As the Director of Patient Outreach at Patients Rising, Jim works very closely with the people to help them tell their stories. Jim is a Columbia University trained writing consultant and has worked closely with writers of all levels of skill to help them find and refine their voices. He is a writer, editor, author and certified medical assistant with over 20 years of experience in healthcare. Jim has spent over two decades in clinical care and research at some of New York’s biggest health institutions doing hands-on patient care, education and advocacy for rare disease patients. He has worked with several non-profit patient support organizations doing outreach, advocacy and creating educational content. Twitter / Linkedin

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