Phesgo (Pertuzumab, Trastuzumab, and Hyaluronidase-Zzxf) for Breast Cancer

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Phesgo (pertuzumab, trastuzumab, and hyaluronidase-zzxf) is a prescription medication approved by the U.S. Food and Drug Administration (FDA) to treat adults with breast cancer.

What Members Say

MHT logo These insights are based on 146 comments about Phesgo from MyBCTeam members. These are the experiences of a small number of people and are not meant to be medical advice.

Benefits:

The thigh injection takes minutes and often reduces time in the clinic.
Every-three-week dosing feels manageable during longer treatment plans.
Side effects sometimes stay mild, with only tiredness, aches, or occasional nausea.

Considerations:

Diarrhea is the most common challenge and can be severe or long-lasting.
Fatigue, weakness, and low energy may occur during treatment.
Heart and lung problems need monitoring, especially with new cough or shortness of breath.

How Phesgo Works and How It’s Taken

Phesgo is a human epidermal growth receptor 2 (HER2) targeted treatment. HER2 is a protein that can help some breast cancer cells grow. Phesgo contains two medicines, pertuzumab and trastuzumab, that attach to different parts of the HER2 protein.

This can help block signals that cancer cells use to grow. These medicines may also help the immune system attack HER2-positive cancer cells. Phesgo also contains hyaluronidase, which helps the medicine spread and be absorbed under the skin to enter the rest of your body.

Doctors prescribe Phesgo to treat certain adults with HER2-positive breast cancer. The exact use depends on the stage of cancer. Phesgo may be used:

With chemotherapy before surgery for early-stage, locally advanced, or inflammatory breast cancer
With chemotherapy after surgery for early-stage HER2-positive breast cancer that has a high risk of coming back
With docetaxel for breast cancer that has spread, in adults who have not already received anti-HER2 treatment or chemotherapy for metastatic disease

Phesgo is given as an injection under the skin on the thigh, usually once every three weeks. It is given by a healthcare professional.

For early breast cancer, treatment is used as part of a full treatment plan before surgery, after surgery, or both. For breast cancer that has spread, treatment usually continues until the cancer gets worse or side effects become unacceptable or intolerable.

Typical Dosing for Breast Cancer

The recommended starting dose of Phesgo for breast cancer is 1,200 milligrams pertuzumab, 600 milligrams trastuzumab, and 30,000 units hyaluronidase given once under the skin.

After that, the recommended maintenance dose is 600 milligrams pertuzumab, 600 milligrams trastuzumab, and 20,000 units hyaluronidase every three weeks.

Doctors may pause treatment, delay the next dose, or stop treatment if side effects are serious or too hard to manage.

This information is based on the prescribing information, but your healthcare provider may tailor your treatment plan. Always follow their guidance.

Top Advice From Members on Phesgo

MHT logo These insights are based on 146 comments about Phesgo from MyBCTeam members.

Members who use Phesgo often say it helps to pay attention to patterns, especially around side effects, injection discomfort, and how treatment fits into daily life. Many also describe checking in with their oncology team when symptoms feel severe, last longer than expected, or seem different from prior treatment.

1

Keep track of side effects after each dose.
“Had my Phesgo injection Thursday and am achy and tired this weekend.”
2

Expect the shot to be quicker than IV treatment.
“Had round two of chemo and targeted therapy earlier today. I wasn’t as anxious as the first round, as I knew what to expect going into it today. I am thankful that I am getting the Phesgo injection instead of Herceptin and Perjeta infusions, which would add probably another two hours in the treatment cycle.”
3

Be patient with recovery, especially hair, nails, and energy.
“It’s been 10 months since I finished chemo and six weeks since my last Phesgo shot. My hair is short but growing back nicely. It’s not as full as it was before chemo, but it seems to be getting better as time goes by. It was slow starting, but coming along better now.”

Connect with others who understand life with breast cancer. Join MyBCTeam for free.

Phesgo Side Effects

The most common side effects of Phesgo depend on how it is being used.

For neoadjuvant and adjuvant treatment of HER2-positive breast cancer, the most common side effects reported in more than 30 percent of people were:

Hair loss
Nausea
Diarrhea
Anemia (low red blood cell levels)
Weakness or low energy

For HER2-positive metastatic breast cancer, the most common side effects are based on studies of IV pertuzumab used with trastuzumab and docetaxel. Side effects reported in more than 30 percent of people were:

Diarrhea
Hair loss
Neutropenia (low levels of certain white blood cells)
Nausea
Fatigue
Rash
Peripheral neuropathy (numbness, tingling, or nerve pain)

Serious Side Effects and Warnings

Phesgo can cause serious side effects that may require immediate medical attention. These include:

Cardiomyopathy — Heart problems, including heart failure, weakened heart function, abnormal heart rhythm, and, rarely, cardiac death can occur.
Fetal harm — Phesgo can harm your baby if you are pregnant, including pregnancy loss and birth defects.
Serious lung problems — Inflammation in the lungs, fluid in or around the lungs, trouble getting enough oxygen, and pulmonary fibrosis can occur.
Severe low white blood cell counts — Febrile neutropenia (low infection-fighting cells with fever) can raise the risk of serious infection.
Severe allergic reactions and administration-related reactions — Anaphylaxis can occur.
Severe hypersensitivity — Serious reactions to pertuzumab, trastuzumab, hyaluronidase, or any ingredient in Phesgo can occur.
Immune thrombocytopenia — A serious drop in platelets can increase bleeding risk.
Glomerulopathy — Kidney damage can occur.
Tumor lysis syndrome — Rapid breakdown of cancer cells can affect the kidneys and blood chemistry.

Get medical help right away if you think you are having a serious reaction.

How To Save on Phesgo

Genentech, the manufacturer of Phesgo, offers the Genentech Oncology Co-pay Assistance Program. Eligible people with commercial insurance may pay as little as $0 per treatment.

The Genentech Oncology Co-pay Assistance Program may offer help with out-of-pocket costs for Genentech Oncology medicines. The program is not available to people whose prescriptions are reimbursed through federal, state, or government-funded insurance programs, such as Medicare, Medicare Advantage, Medigap, Medicaid, Veterans Affairs, Department of Defense, or TRICARE.

To learn more, visit CopayAssistanceNow.com or call 855-692-6729.

What To Know Before Taking Phesgo

Before starting Phesgo, your doctor will test or check for HER2-positive breast cancer and your heart function, including left ventricular ejection fraction.

Tell your doctor if you have any allergies to pertuzumab, trastuzumab, hyaluronidase-zzxf, or any ingredients in Phesgo.

Tell your doctor about all medications you take, including prescription drugs, over-the-counter medicines, and supplements.

Do not take Phesgo if you have had a serious allergic reaction to pertuzumab, trastuzumab, hyaluronidase, or any of its ingredients.

Phesgo can harm your baby if you are pregnant. Your doctor may give you a pregnancy test before you start treatment. Females who can become pregnant should use effective birth control during treatment and for seven months after the last dose.

If you are breastfeeding, talk with your doctor because it is not known if Phesgo passes into human milk, and the seven-month washout period should be considered.

Community FAQs

These answers are fact-checked by our editorial staff.

How effective is Phesgo?

In a study of people with HER2-positive early breast cancer, 59.7 percent of people who received Phesgo had a pathologic complete response. This means no invasive cancer was found in the breast or lymph nodes at surgery.

In the same study, 59.5 percent of people who received IV pertuzumab plus trastuzumab had this response. The difference between the groups was 0.15 percent. This means the medications work very similarly, though they are given in different ways — injection under the skin versus intravenous infusion.

For HER2-positive metastatic breast cancer, Phesgo’s use is based on studies of IV pertuzumab and trastuzumab used with docetaxel. It is also based on pharmacokinetic and safety data for Phesgo. Pharmacokinetic data shows how a medicine moves through the body.

Can Phesgo cause diarrhea in people with breast cancer?

Yes. In the FeDeriCa trial in early breast cancer, diarrhea was reported in 60 percent of people who received Phesgo, and 7 percent had dose interruptions because of diarrhea. Diarrhea was also one of the most common side effects seen with pertuzumab-based treatment in metastatic breast cancer.

What tests or monitoring are needed with Phesgo for breast cancer?

Cardiac monitoring is an important part of treatment. Before starting Phesgo, people need a cardiac assessment that includes left ventricular ejection fraction, usually checked by echocardiogram or MUGA scan, and this is assessed at regular intervals during treatment. After finishing adjuvant treatment, cardiac monitoring continues every six months for at least two years.