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Herceptin Hylecta

Generic name: trastuzumab and hyaluronidase-oysk
Dosage form: subcutaneous injection
Drug class: HER2 inhibitors

Medically reviewed by Philip Thornton, DipPharm. Last updated on Apr 4, 2023.

What is Herceptin Hylecta?

Herceptin Hylecta (trastuzumab and hyaluronidase-oysk) is a type of targeted immunotherapy used in the treatment of HER2 (human epidermal growth factor receptor 2)-positive breast cancers. HER2-positive breast cancer cells overexpress - have excessive amounts of - the HER2 receptor protein on their surface. HER2 (previously called HER2/Neu) helps cancer cells to grow and divide quickly.

Herceptin Hylecta contains a monoclonal antibody known as trastuzumab. Trastuzumab is a HER2 inhibitor. It works by targeting and binding to HER2, which stops the cancer cells from growing and dividing. Trastuzumab initiates antibody-dependent cell-mediated cytotoxicity (ADCC), which means it gets your own immune system cells to target and kill the cancer cells that are coated with antibodies.

Herceptin Hylecta is administered over 2-5 minutes via a quick subcutaneous injection under the skin, unlike Herceptin which is an intravenous (IV) trastuzumab product that is administered via infusion into a vein or port over 30-90 minutes. The quick administration of Herceptin Hylecta is made possible by the addition of hyaluronidase, which is an enzyme that works temporarily at the injection site to facilitate the absorption of trastuzumab into the blood stream.

Herceptin Hylecta was approved by the US Food and Drug Administration (FDA) in 2019.

What is Herceptin Hylecta used for?

Herceptin Hylecta is a prescription medication used for adults with:

Patients are selected for treatment based on an FDA-approved companion diagnostic for trastuzumab.

Important information

Herceptin Hylecta may cause serious side effects including:

Who should not receive Herceptin Hylecta?

Do not receive Herceptin Hylectra if you are allergic to trastuzumab or any of the other ingredients in it. See below for a complete list of ingredients.

What should I tell my doctor before receiving Herceptin Hylecta?

Before receiving Herceptin Hylecta, tell your healthcare provider about all of your medical conditions including if you:

How should I receive Herceptin Hylecta?

What happens if I miss a dose?

If you miss a dose of Herceptin Hylecta, contact your healthcare provider and arrange to have it administered as soon as possible. The interval between subsequent injections should not be less than 3 weeks.

What should I avoid while receiving Herceptin Hylecta?

Trastuzumab, the active ingredient in this medication, may affect your ability to drive a car or operate machines. If during treatment, you experience symptoms, such as dizziness, sleepiness, chills or fever, you should not drive or use machines until these symptoms disappear.

Dosing information

The recommended dose of Herceptin Hylecta is 600 mg/10,000 units (600 mg trastuzumab and 10,000 units hyaluronidase) administered subcutaneously over approximately 2-5 minutes once every three weeks.

See full prescribing information for further details about dosing.

What are the side effects of Herceptin Hylecta?

Herceptin Hylecta can cause serious side effects:

The most common side effects of Herceptin Hylecta seen in patients with adjuvant breast cancer are:

The most common side effects of Herceptin Hylecta seen in patients with metastatic breast cancer (based on intravenous trastuzumab) are:

These are not all the possible side effects of this medication.

You should contact your doctor immediately if you have any of the side effects listed above. You may report side effects to the FDA at 1‑800‑FDA‑1088 or You may also report side effects to Genentech at 1‑888‑835‑2555.


Tell your healthcare provider about all the medicines you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

Especially tell your doctor if you are prescribed an anthracycline drug after stopping Herceptin Hylecta. It is recommended to avoid anthracycline-based therapy for up to 7 months after stopping Herceptin Hylecta.

Pregnancy and breastfeeding

Tell your healthcare provider if you are pregnant or plan to become pregnant. Herceptin Hylecta may result in the death of an unborn baby or birth defects. Contraception should be used while receiving treatment and for 7 months after your last dose of this medication. If you are or become pregnant while receiving this medication or within 7 months after your last dose, healthcare providers and patients should report Herceptin Hylecta exposure to Genentech at 1‑888‑835‑2555 straight away.

Tell your healthcare provider if you are breastfeeding or plan to breastfeed. It is not known if Herceptin Hylecta is present in human breast and what effects it may have on breastfeed infants or milk production. Talk to your doctor about the best way to feed your baby while on this medication and for 7 months afterwards.


What are the ingredients in Herceptin Hylecta?

Active ingredients: trastuzumab and hyaluronidase

Inactive ingredients: L-histidine, L-histidine hydrochloride monohydrate, L-methionine, polysorbate 20, α,αtrehalose dihydrate, and Water for Injection.

Frequently asked questions

View more FAQ

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.