Phesgo (chemical name: pertuzumab, trastuzumab, and hyaluronidase-zzxf) is a fixed-dose combination of Herceptin (chemical name: trastuzumab), Perjeta (chemical name: pertuzumab), and hyaluronidase-zzxf to treat all stages of HER2-positive breast cancer in combination with chemotherapy.
Hyaluronidase-zzxf is an enzyme that helps the body absorb Herceptin and Perjeta.
Phesgo can be used in combination with chemotherapy:
- before surgery for early-stage or inflammatory HER2-positive breast cancer
- after surgery for early-stage HER2-positive breast cancer with a high risk of recurrence
Phesgo also can be used in combination with Taxotere (chemical name: docetaxel) to treat HER2-positive metastatic breast cancer that has not been treated with anti-HER2 therapy or chemotherapy.
Phesgo is given as an injection under the skin in the thigh. When a medicine is injected under the skin, it’s called a subcutaneous injection.
Learn more about:
- How Phesgo works
- Is Phesgo right for you?
- What to expect when receiving Phesgo
- Paying for Phesgo
- Phesgo side effects
Some cancer cells have abnormalities in genes that tell the cell how much and how fast to grow. Sometimes the cancer cells have too many copies of these genes with abnormalities. When there are too many copies of these genes, doctors refer to it as "overexpression." With some forms of gene overexpression, cancer cells will make too many of the proteins that control cell growth and division, causing the cancer to grow and spread.
Some breast cancer cells make too many copies of (overexpress) a particular gene known as HER2. The HER2 gene makes a protein known as a HER2 receptor. HER2 receptors are like ears, or antennae, on the surface of all cells. These HER2 receptors receive signals that stimulate the cell to grow and multiply. But breast cancer cells with too many HER2 receptors can pick up too many growth signals and start growing and multiplying too much and too fast. Breast cancer cells that overexpress the HER2 gene are said to be HER2-positive.
Both Herceptin and Perjeta are HER2 inhibitors. They work against HER2-positive breast cancer by blocking the chemical signals that tell the cancer cells to grow.
Traditionally, Herceptin and Perjeta are given intravenously, which means they’re delivered directly into your bloodstream through an IV or a port. The first dose of both medicines takes about an hour to complete. After that, it takes 30 to 60 minutes to get each dose.
Phesgo combines fixed doses of Herceptin and Perjeta, plus hyaluronidase-zzxf, in one vial. Phesgo is injected under the skin into a person’s thigh. The first dose of Phesgo takes about 8 minutes to inject and each dose after that takes about 5 minutes, so the time to receive each dose is much shorter than getting an intravenous infusion of the medicines.
Because it’s given as an injection, a healthcare professional can give you Phesgo in your home, avoiding a trip to a treatment center.
There are several tests used to find out if breast cancer is HER2-positive. Two of the most common tests are:
The IHC test uses a chemical dye to stain the HER2 proteins. The IHC gives a score of 0 to 3+ that measures the amount of HER2 proteins on the surface of cells in a breast cancer tissue sample. If the score is 0 to 1+, it’s considered HER2-negative. If the score is 2+, it's considered borderline. A score of 3+ is considered HER2-positive.
If the IHC test results are borderline, it’s likely that a FISH test will be done on a sample of the cancer tissue to determine if the cancer is HER2-positive.
FISH (Fluorescence In Situ Hybridization)
The FISH test uses special labels that are attached to the HER2 proteins. The special labels have chemicals added to them so they change color and glow in the dark when they attach to the HER2 proteins. This test is the most accurate, but it is more expensive and takes longer to return results. This is why an IHC test is usually the first test done to see if a cancer is HER2-positive. With the FISH test, you get a score of either positive or negative (some hospitals call a negative test result “zero”).
Learn more about HER2 status.
For early-stage or inflammatory HER2-positive breast cancer, Phesgo is prescribed with chemotherapy. Depending on the chemotherapy regimen you’ve been prescribed, you may get Phesgo either before or after chemotherapy.
For metastatic HER2-positive breast cancer that hasn’t been treated with anti-HER2 medicine or chemotherapy, Phesgo is prescribed with Taxotere. You will get Phesgo first, then the Taxotere.
Phesgo is given as an injection under the skin into your thigh. The first dose of Phesgo takes about 8 minutes to inject and each dose after that takes about 5 minutes, so the time to receive each dose is much shorter than getting an intravenous infusion of the medicines.
Some people may have allergic reactions at the injection site when being treated with Phesgo. The healthcare provider who gives you the Phesgo injection will closely monitor you for 30 minutes after your first dose. For later doses, you will be monitored for 15 minutes.
Women who are pregnant or are planning to get pregnant should not be given Phesgo. Phesgo can cause embryo death and birth defects. It’s important that you don’t get pregnant while you’re getting Phesgo; you must use effective birth control while you’re being treated with Phesgo and for at least 7 months after your last dose.
If your doctor prescribes Phesgo and you have any problems getting it covered by insurance or don’t have insurance, you can get in touch with Access Solutions, sponsored by Genentech, the maker of Phesgo. Access Solutions can help investigate your insurance coverage benefits, appeal denied claims, and provide other assistance. You also can call Access Solutions at 1-877-436-3683.
Phesgo side effects
The most common side effects of Phesgo when given with chemotherapy to treat early-stage HER2-positive breast cancer are:
The most common side effects of Phesgo when given with Taxotere to treat metastatic HER2-positive breast cancer are:
- hair loss
- low white blood cell levels
- peripheral neuropathy (numbness, tingling, or pain in the hands and feet)
Phesgo also may cause serious side effects, including:
- Heart problems: Phesgo may cause serious heart problems, including some that don’t have symptoms, such as reduced heart function, and some that do have symptoms, such as congestive heart failure. Symptoms to watch for include swelling of the ankles or legs, shortness of breath, cough, or weight gain of more than 5 pounds in less than 24 hours. Contact your doctor immediately if you have any of these symptoms. Your risk of heart problems is higher if you are receiving Phesgo in combination with anthracycline chemotherapy.
- Lung problems: Phesgo may cause inflammation of the lungs, which can be life-threatening. Symptoms include trouble breathing, cough, tiredness, and fluid in the lungs.
- Severe neutropenia: Neutropenia means you have abnormally low levels of neutrophils, a type of white blood cell. People with neutropenia have a much higher risk of getting serious infections. Your doctor will monitor your neutrophil counts while you are being treated with Phesgo.
- Injection site reactions: Because Phesgo is given as an injection, a small number of people have had reactions at the injection site or anaphylaxis. Anaphylaxis is a severe allergic reaction that can cause hives, low blood pressure, dizziness, chills, and trouble breathing. The healthcare provider who gives you the Phesgo injection will closely monitor you for 30 minutes after your first dose. For later doses, you will be monitored for 15 minutes. Tell your doctor immediately if you have any of the symptoms of anaphylaxis.
- Phesgo (pertuzumab, trastuzumab, and hyaluronidase-zzxf) prescribing information. 2020. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2020/761170s000lbl.pdf. (PDF)
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