Phesgo is a fixed-dose combination of two targeted cancer-fighting antibodies, pertuzumab and trastuzumab, administered as a subcutaneous injection. It is used to treat HER2-positive breast cancer, a more aggressive form of cancer where cells produce too much of the HER2 protein. This combination therapy was developed to make treatment more convenient, avoiding the need for long intravenous infusions while maintaining the proven effectiveness of the drugs.

Phesgo offers an efficient and time-saving alternative for eligible patients, supporting their care without compromising outcomes.

Mechanism of Action

Phesgo works by targeting the HER2 receptor, a protein found in high amounts on the surface of certain cancer cells. Both pertuzumab and trastuzumab are monoclonal antibodies, but they attach to different parts of the HER2 receptor, blocking cancer growth in a complementary way.

• Trastuzumab binds to a specific region of the HER2 receptor, blocking signals that encourage cancer cells to grow and divide. It also helps the immune system recognize and attack these cells.

• Pertuzumab binds to a different area of the same receptor, preventing the receptor from pairing with other HER family proteins, which is another way cancer cells try to grow.

  Uses

  Phesgo is used in the treatment of HER2-positive breast cancer, both in early and advanced stages. It may be given in combination with chemotherapy.

  Key indications include:

  • Early breast cancer that is at high risk of returning

  • Metastatic breast cancer, where the disease has spread beyond the breast

  • As part of neoadjuvant (before surgery) and adjuvant (after surgery) therapy

    Adverse Effects

    Phesgo is generally well-tolerated and offers the convenience of a single injection. However, as with any cancer treatment, it can cause side effects. These are typically manageable and may vary in severity from person to person.

    Common Side Effects

    • Hair loss

    • Nausea

    • Diarrhea

    • Fatigue

    • Low white blood cell count

    • Pain in joints or muscles

    • Reactions at the injection site such as redness, swelling, or discomfort