What Is Phesgo™ (pertuzumab, trastuzumab, and hyaluronidase-zzxf)?

Reviewed by: HU Medical Review Board | Last reviewed: June 2023

Phesgo™ (pertuzumab, trastuzumab, and hyaluronidase-zzxf) is a drug used to treat certain forms of breast cancer that are positive for the human epidermal growth factor receptor 2 (HER2+).1

Phesgo can be used with chemotherapy in these cases:1,2

  • Before surgery to treat early-stage, locally advanced, or inflammatory HER2-positive breast cancer
  • After surgery to treat early-stage HER2-positive breast cancer that has a high risk of recurrence (coming back)
  • With the chemotherapy drug docetaxel to treat HER2-positive metastatic (has spread to other parts of the body) breast cancer that has not been treated with anti-HER2 therapy or chemotherapy

Phesgo is given by injection under the skin (a shot). Before, trastuzumab and pertuzumab could only be given through an intravenous (IV) infusion. Phesgo can be given at home by a home health nurse. This helps people avoid extra trips to an infusion center.1

How does Phesgo work?

Breast cancers that are HER2+ have too many HER2 receptors. Pertuzumab targets these receptors and blocks them, which can lead to the cancer cells' death. Trastuzumab also targets HER2 receptors, but pertuzumab and trastuzumab work on different parts of this receptor. Combining pertuzumab with trastuzumab and chemotherapy can target the cancer cells in multiple ways.1

What are the possible side effects?

The most common side effects of Phesgo, depending on the specific form of breast cancer being treated, include:1

  • Diarrhea
  • Hair loss
  • Low white blood cell levels
  • Nausea
  • Fatigue
  • Rash
  • Numbness, tingling, or pain in the hands and feet (peripheral neuropathy)
  • Low red blood cell levels
  • Weakness

Phesgo may also cause injection-related reactions. Signs may include:1

  • Dizziness
  • Nausea, vomiting
  • Chills, fever
  • Diarrhea
  • Itching
  • Chest pain

Phesgo has a boxed warning, the strictest warning from the U.S. Food and Drug Administration (FDA). This is because it may cause severe side effects, including:1,2

  • Heart problems, such as heart failure
  •  Birth defects or death in unborn babies
  • Lung problems, including a life-threatening inflammation of the lungs

These are not all the possible side effects of Phesgo. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with Phesgo.

Other things to know

Your doctor will monitor your heart function before and during treatment with Phesgo.2

Phesgo can harm an unborn baby. If you can become pregnant, you should use birth control during treatment and for some time after the last dose of Phesgo. You should also not breastfeed during treatment with DrugName and for some time after the last dose. Talk to your doctor about your options for birth control and breastfeeding while taking Phesgo.2

Before beginning treatment for breast cancer, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

For more information, read the full prescribing information of Phesgo.

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