Kanjinti (chemical name: trastuzumab-anns), a biosimilar for Herceptin used to treat people diagnosed with HER2-positive breast cancer, is now available in the United States.
Amgen and Allergan, the companies that make Kanjinti, said the cost for Kanjinti will be 15% lower than the wholesale acquisition cost of Herceptin. The wholesale acquisition cost is the estimated manufacturer’s list price for a drug to wholesalers or direct purchasers, but doesn’t include discounts or rebates.
Kanjinti 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
- as a single treatment after people have been treated with anthracycline-based chemotherapy
Kanjinti 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
Kanjinti can also be used to treat metastatic, HER2-positive stomach cancer.
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 the makers of biosimilars to show that a biosimilar drug is "highly similar" to the original biologic drug and is equally safe and effective before the agency will approve the biosimilar.
What this means for you
In the United States, access to Herceptin usually isn’t a problem for people diagnosed with HER2-positive breast cancer. Almost all insurance companies cover Herceptin to treat HER2-positive disease.
Still, if you don’t have insurance or are under-insured, the cost of Herceptin may be overwhelming for you. It’s expected that having a biosimilar available will reduce Herceptin treatment costs.
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 Sept. 27, 2019, to clarify information about biosimilars.
Written by: Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser