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Overview: Phesgo is used to treat certain breast cancers. Common side effects include hair loss, diarrhea, and nausea. Call your health care provider right away if you get a fever, cough, or new or worsening breathing problems. Phesgo is a shot under your skin (subcutaneous injection) given to you by a health care provider.

Uses

What is Phesgo used for?

Phesgo (pertuzumab/trastuzumab/hyaluronidase-zzxf) is commonly used to treat certain types of HER2-positive breast cancer.

Phesgo may also be used for other conditions as determined by your health care provider.

How does Phesgo work (mechanism of action)?

Phesgo has three active medicines: pertuzumab, trastuzumab, and hyaluronidase. Pertuzumab and trastuzumab block certain proteins, known as HER2, on the cancer cells. By blocking these proteins, Phesgo can cause cancer cells to die and can prevent cancer cells from growing or spreading. Hyaluronidase helps to increase the ability of your skin to absorb Phesgo into your body, which allows Phesgo to be given as a subcutaneous (under-the-skin) shot. 

How is Phesgo supplied (dosage forms)?

Brands and other names

  • Phesgo

Dosage forms and strengths

Phesgo is available in an injectable form that is given by a health care provider.

How should I store Phesgo?

Phesgo is usually given by a health care provider in a hospital or clinic. You will not store it at home.

Side Effects

What are the most common side effects of Phesgo?

The most common side effects of Phesgo are listed below. Tell your health care provider if you have any of these side effects that bother you.

  • Hair loss
  • Nausea
  • Diarrhea
  • Blood disorders including low red blood cells (anemia) and low neutrophil levels (neutropenia)
  • Feeling unusually weak or tired
  • Rash
  • Pain, burning, tingling, numbness, or weakness in your arms, hands, legs, or feet

There may be other side effects of Phesgo that are not listed here. Contact your health care provider if you think you are having a side effect of a medicine. In the U.S., you can report side effects to the FDA at www.fda.gov/medwatch or by calling 800-FDA-1088. In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of Phesgo?

While less common, the most serious side effects of Phesgo are described below, along with what to do if they happen.

Severe Allergic Reactions. Phesgo may cause allergic reactions, which can be serious. Get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching, skin rash, or pale red bumps on the skin called hives
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Lung Problems. Phesgo can cause lung damage, fluid to build up in your lungs, and inflammation in your lungs, also called interstitial lung disease or pneumonitis. This can be serious or even life-threatening. These problems may be more serious if you already have lung problems, including cancer that has spread to your lungs. Get emergency help if you have trouble breathing. You may also have a cough, fever, or chest pain. 

Heart Failure. Phesgo may increase your risk of heart failure. Keep all appointments to have your heart checked. Tell your health care provider right away if you have any of the following symptoms of heart failure.

  • Shortness of breath or trouble breathing, especially while lying down
  • Cough
  • Swelling in your feet, ankles, or legs
  • Unusually fast weight gain
  • Unusual tiredness
  • Skipping heart beats
  • Dizziness
  • Fainting

Injection Reactions. Phesgo can cause injection reactions that can be serious when it is given to you. Your injection may need to be slowed or stopped if you have these reactions. Tell your health care provider right away if you have pain, itching, or redness where you get your medicine.

Low Neutrophil Levels. Phesgo may cause low levels of a type of white blood cell (called neutrophils), which is known as neutropenia. Neutrophils help prevent infection. Having a low level of neutrophils may increase your risk of infection. Tell your health care provider right away if you have any of the following symptoms of low neutrophil levels.

  • Fever, chills, or sweats
  • Tiredness
  • Sore throat, cough, or shortness of breath
  • Mouth or throat sores
  • Swollen lymph nodes

Warnings & Precautions

Who should not use Phesgo?

Allergies to Ingredients. People who are allergic to any of the following should not use Phesgo.

  • Pertuzumab
  • Trastuzumab
  • Hyaluronidase
  • Phesgo
  • Any of the ingredients in the specific product dispensed

Your pharmacist can tell you all of the ingredients in Phesgo.

What should I know about Phesgo before using it?

Phesgo is usually given by a health care provider in a hospital or clinic. 

What should I tell my health care provider before using Phesgo?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if Phesgo is right for you.

In particular, make sure that you discuss any of the following.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Heart problems, such as arrhythmias or heart attack
  • High blood pressure
  • Lung problems

Other Medicines and Supplements. Phesgo may interact with other medicines and supplements. Before using Phesgo, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. Phesgo may harm an unborn baby. Your health care provider will give you a test to make sure you are not pregnant before you start using Phesgo. If you can get pregnant, you should use birth control while using Phesgo and for seven months after your last dose. Tell your health care provider right away if you are pregnant or plan to become pregnant.

If you become pregnant while using Phesgo or in the seven months after your last dose, call the drugmaker at 888-835-2555 to take part in a pregnancy program to monitor how your pregnancy goes.

Breastfeeding. It is not known if Phesgo passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

How can I get more information about Phesgo?

For more information about Phesgo, you can visit the drugmaker’s website at www.phesgo.com or call them at 877-436-3683.

Interactions

Does Phesgo interact with foods or drinks?

There are no known interactions between Phesgo and foods or drinks.

It is unknown if drinking alcohol will affect Phesgo, but heavy drinking can slow your immune response and make it harder for your body to fight cancer.

Does Phesgo interact with other medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any other medicines to treat cancer before starting to use Phesgo. 

It is also important to tell any health care provider you see after your last dose of Phesgo that you previously used Phesgo. This is because it stays in your body for up to seven months and may interact with certain medicines.

This may not be a complete list of medicines that can interact with Phesgo. Always check with your health care provider.

Does interact with other drugs you are taking?

Enter your medication into the WebMD interaction checker

Overdose/Missed Dose

What should I do if I accidentally use too much Phesgo?

If you or someone else has used too much Phesgo, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

What should I do if I miss a dose of Phesgo?

Phesgo is usually given by a health care provider in a hospital. Your health care provider will make sure you are receiving Phesgo as scheduled. If you miss an appointment to get your Phesgo dose, call to make another appointment as soon as possible.