On Dec. 14, 2018, the U.S. Food and Drug Administration (FDA) approved Herzuma (chemical name: trastuzumab-pkrb), a biosimilar for Herceptin (chemical name: trastuzumab), to treat people with HER2-positive breast cancer.
Herzuma is approved to treat non-metastatic HER2-positive breast cancer that has spread to the lymph nodes (node-positive), or is not in the lymph nodes but is considered to be at high risk of recurrence:
- after surgery as part of a treatment regimen that includes Adriamycin (chemical name: doxorubicin), Cytoxan (chemical name: cyclophosphamide), and either Taxol (chemical name: paclitaxel) or Taxotere (chemical name: docetaxel)
- after surgery as part of a treatment regimen with Taxotere and carboplatin
Herzuma is also approved to treat metastatic HER2-positive breast cancer:
- in combination with Taxol as the first treatment for metastatic disease
- as a single treatment for people who have been treated with one or more chemotherapy regimens for metastatic disease
Metastatic breast cancer is cancer that has spread to parts of the body away from the breast, such as the bones or liver.
Herzuma was previously known as CT-P6 and is made by Celltrion and Teva.
What are biosimilars?
Herceptin (chemical name: trastuzumab) is a monoclonal antibody, a targeted therapy medicine used to treat HER2-positive breast cancers. Herceptin is what’s called a “biologic” drug. This means that it is made from living organisms — in this case, a protein from a mouse cell. A monoclonal antibody is a type of protein made in the lab that can bind to substances in the body, including cancer cells. Each monoclonal antibody is made so that it binds only to one substance. Herceptin binds to the HER2 receptor proteins in cancer cells.
Because they are made from living organisms, biologic drugs are much more complex to make than conventional drugs that are made from a mixture of chemicals. The chemical structure of conventional drugs can be easily identified and duplicated, which is why there are so many generic drugs on the market.
A biosimilar is a new type of biologic drug. A biosimilar is almost identical to a biologic drug that is already approved by the FDA (or similar organizations in other countries). It can help to think of a biosimilar as a generic version of a biologic drug, though that comparison isn’t completely accurate.
The makers of biosimilars don’t have access to the original cell lines used to make the biologic drug. They also don’t have access to the exact purification process or other manufacturing steps used by the makers of the biologic drug.
Biologic drugs can be very sensitive to changes in the manufacturing process. If one small step is done differently, the biosimilar may have very different effects than the original biologic drug.
So, the FDA requires that any biosimilar drug go through the same rigorous clinical trials that original biologic drugs do before the agency will approve the biosimilar.
The FDA’s approval of Herzuma is based on review of evidence that included extensive studies on the drug’s structure and function, animal study data, studies on how the drug is absorbed and metabolized by the human body, studies on how the drug affects people, and other clinical safety and effectiveness data that demonstrate Herzuma is biosimilar to Herceptin.
The FDA emphasized that Herzuma has been approved as a biosimilar, not as a product that is interchangeable with Herceptin. This means that if you start treatment with Herceptin, you can’t switch to Herzuma in the middle of treatment. Similarly, if you start treatment with Herzuma, you can’t switch to Herceptin in the middle of treatment.
The approval is based on research showing that Herzuma is as effective and as safe as Herceptin.
Herzuma side effects
Like Herceptin, Herzuma can cause side effects, some of them severe. Common Herzuma side effects include:
- heart problems
Serious side effects include worsening of neutropenia (low white blood cell count) caused by chemotherapy.
Like Herceptin, less common but more severe side effects of Herzuma include weakening of the heart muscle and other heart problems.
What does this mean for you?
In the United States, access to Herceptin is not usually a problem for people diagnosed with HER2-positive breast cancer. Almost all insurance companies cover Herceptin to treat HER2-positive disease.
Still, in other countries, the cost of Herceptin can mean that some women don’t receive the treatment. It’s expected that having a biosimilar will reduce treatment costs around the world.
Right now, it’s not clear when Herzuma will be available in the United States or how much Herzuma will cost.
Stayed tuned to Breastcancer.org for the latest information on Herzuma and other biosimilar drugs for breast cancer.
To talk with others diagnosed with HER2-positive breast cancer and making treatment decisions, join the Breastcancer.org Discussion Board forum HER2+ (Positive) Breast Cancer.
Editor’s Note: This article was updated on March 23, 2019, with clarifications about the chemotherapy regimens used with Herzuma.
Written by: Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser