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Generic name: hyaluronidase, pertuzumab, and trastuzumabHYE-al-ure-ON-i-dase, per-TOOZ-ue-mab, and-tras-TOOZ-ue-mab ]
Drug class: HER2 inhibitors

Medically reviewed by Philip Thornton, DipPharm. Last updated on Aug 7, 2023.

What is Phesgo?

Phesgo contains a combination of hyaluronidase, pertuzumab, and trastuzumabis.

Phesgo is a cancer medicine that is used alone or with other medicines to treat early-stage breast cancer.

Phesgo is also used to treat HER2-positive breast cancer that is advanced or has spread to other parts of the body (metastatic).

Phesgo is used for breast cancer only if your tumor tests positive for a protein called human epidermal growth factor receptor 2 (HER2). HER2 protein can speed the growth of cancer cells.


Phesgo can cause life-threatening heart or lung problems. Call your doctor at once if you have trouble breathing, swelling or rapid weight gain, fast or pounding heartbeats, or if you feel light-headed.

Do not use if you are pregnant. Use effective birth control during treatment and for at least 7 months after your last dose.

Before taking this medicine

You should not be treated with Phesgo if you are allergic to hyaluronidase, pertuzumab, or trastuzumab.

To make sure Phesgo is safe for you, tell your doctor if you have ever had:

You may need to have a negative pregnancy test before starting this treatment.

Do not use Phesgo if you are pregnant. It could cause birth defects or death to the unborn baby. Use effective birth control to prevent pregnancy while you are using Phesgo and for at least 7 months after your last dose. Tell your doctor right away if you think you might be pregnant.

If you are pregnant or you become pregnant within 7 months after being treated with this medicine: Your name may be listed on a pregnancy registry to track the effects of hyaluronidase, pertuzumab, and trastuzumab on the baby.

It may not be safe to breastfeed while using Phesgo. Ask your doctor about any risk.

How is Phesgo given?

Phesgo is injected under the skin of your thigh. A healthcare provider will give you this injection.

Phesgo is usually given once every 3 weeks for up to 1 year. Your doctor will determine how long to treat you with this medicine.

You will be watched closely for 15 to 30 minutes to make sure you do not have a serious reaction to the injection.

Phesgo can have long lasting effects on your heart. Your heart function may need to be checked every 6 months for at least 2 years after your last dose.

For at least 7 months after your last dose of Phesgo, make sure any doctor treating you with chemotherapy knows that you have received this medicine.

What happens if I miss a dose?

Call your doctor for instructions if you miss an appointment for your Phesgo.

What happens if I overdose?

Since Phesgo is given by a healthcare professional in a medical setting, an overdose is unlikely to occur.

What should I avoid while receiving Phesgo?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

Phesgo side effects

Get emergency medical help if you have signs of an allergic reaction to Phesgo: hives, rash; fever, chills, dizziness; nausea, vomiting, diarrhea; chest pain, difficult breathing; swelling of your face, lips, tongue, or throat.

Phesgo can cause life-threatening heart or lung problems. Call your doctor at once if you have:

Your cancer treatments may be delayed or permanently discontinued if you have certain side effects.

Common Phesgo side effects may include:

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Phesgo?

Other drugs may affect Phesgo, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Phesgo only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.