On Jan. 18, 2019, the U.S. Food and Drug Administration (FDA) approved Ontruzant (chemical name: trastuzumab-dttb), a biosimilar for Herceptin (chemical name: trastuzumab), to treat people diagnosed with HER2-positive breast cancer.
The FDA did not issue an official press announcement about this approval.
Ontruzant 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
Ontruzant 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
Ontruzant also can be used to treat metastatic stomach cancer.
Metastatic breast cancer is cancer that has spread to parts of the body away from the breast, such as the bones or liver.
Ontruzant is given by intravenous (IV) infusion, which means the medicine is delivered directly into your bloodstream through an IV or a port.
Ontruzant is made by Samsung Bioepis and will be marketed and distributed in the United States by Merck. Ontruzant also is approved by the European Commission.
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 that 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 Ontruzant 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 Ontruzant is biosimilar to Herceptin.
Ontruzant 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 Ontruzant in the middle of treatment. Similarly, if you start treatment with Ontruzant, you can’t switch to Herceptin in the middle of treatment.
The approval is based on research showing that Ontruzant is as effective and as safe as Herceptin.
Ontruzant side effects
Like Herceptin, Ontruzant can cause side effects, some of them severe. Common Ontruzant side effects include:
- heart problems
Like Herceptin, less common but more severe side effects of Ontruzant include weakening of the heart muscle and other heart problems, as well as serious lung problems.
What this means 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 people 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 Ontruzant will be available in the United States or how much Ontruzant will cost.
Stayed tuned to Breastcancer.org for the latest information on Ontruzant 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 19, 2019, to correct the FDA approval date for Ontruzant (from Jan. 20 to Jan. 18, 2019).
Written by Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser