What is Phesgo™?

Phesgo™ is a drug used to treat breast cancer that is positive for the human epidermal growth factor receptor 2 (HER2+). It is used in combination with chemotherapy. Phesgo includes 2 drugs, trastuzumab and pertuzumab, both of which target cancer cells that are HER2+, plus the enzyme hyaluronidase-zzxf. This enzyme helps the body absorb the medicines.1

Phesgo is given by injection under the skin (a shot). Before, trastuzumab and pertuzumab could only be given through an intravenous (IV) infusion.1

Phesgo can be given at home by a home health nurse. This helps patients avoid extra trips to an infusion center.

It is injected into the thigh in doses that can be administered over several minutes. This makes it quicker to receive the drug compared to getting it through an IV or port.1

How does Phesgo work?

Breast cancers that are HER2+ have an excess of HER2 receptors. Pertuzumab targets these receptors and blocks them, which can lead to the cancer cell’s 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

Phesgo can be used with chemotherapy in these cases1,2:

  • 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 Taxotere (chemical name: 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

What are the possible side effects of Phesgo?

The 2 drugs that make up Phesgo, trastuzumab and pertuzumab, can cause slightly different side effects in patients with early-stage or late-stage cancers.1-2

The most common side effects of Phesgo in patients with early-stage HER2-positive breast cancer include:1:

  • Hair loss
  • Nausea
  • Diarrhea
  • Low red blood cell levels
  • Weakness

The most common side effects of Phesgo in patients with metastatic HER2-positive breast cancer, when given with Taxotere include1:

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

Possible severe side effects of Phesgo include:1,2:

  • Heart problems, including high blood pressure, irregular heartbeat (arrhythmias), left ventricular cardiac dysfunction, disabling cardiac failure, cardiomyopathy, and sudden death due to a heart problem (cardiac death)
  • Harm to the baby in pregnant women
  • Lung problems, including a life-threatening inflammation of the lungs
  • Worsening of chemotherapy-induced reductions in white blood cells
  • Reaction at the injection site.
  • A small number of people have a serious allergic reaction called anaphylaxis. Symptoms of anaphylaxis may include hives, low blood pressure, dizziness, chills, and trouble breathing.

These are not all of the possible side effects of Phesgo. Talk to your doctor about Phesgo and what to expect with treatment.

Things to know about Phesgo

When receiving Phesgo, your home health nurse should monitor you for possible reactions for 30 minutes after the first dose. You should also be monitored for reactions for 15 minutes after each subsequent dose.2

Phesgo is not recommended for anyone with a known hypersensitivity to pertuzumab, or trastuzumab, or hyaluronidase, or any related drugs.2

Because Phesgo can cause birth defects or fatal harm to an unborn fetus, women who can become pregnant who receive Phesgo should use birth control during their treatment and for a period of time after completing treatment (patients should discuss appropriate birth control methods, and how long they need to use them, with their doctor).

Patients should talk to their doctor if they have any questions, or if they have questions regarding their Phesgo regimen. Before starting treatment with Phesgo, patients should tell their doctor about all their health conditions, as well as any medications (prescription and over-the-counter), herbal supplements, and vitamins they are taking.

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

Written by: Editorial Team | Last reviewed: October 2020