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Brand name: Ontruzant

Chemical name: Trastuzumab-dttb

Class: HER2 (human epidermal receptor 2) inhibitor targeted therapy. Herceptin, Herzuma, Kanjinti, Nerlynx, Ogivri, Perjeta, Trazimera, and Tykerb are other HER2 inhibitors.

Uses: Ontruzant typically is used to:

  • treat metastatic, HER2-positive breast cancer
  • reduce the risk of early-stage, HER2-positive disease coming back after surgery and other treatments as part of a regimen with chemotherapy medicines

How it’s given: Ontruzant is given intravenously.

Additional information: Ontruzant is a biosimilar of Herceptin. Herceptin is a monoclonal antibody, “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 U.S. Food and Drug Administration (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.

Ontruzant is 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.

Side effects:

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