trastuzumab
Herceptin (trastuzumab) is a humanized monoclonal antibody from Roche that targets the HER2 receptor on cancer cells. It treats HER2-overexpressing breast cancer in early and metastatic settings and HER2-overexpressing metastatic gastric or gastroesophageal junction adenocarcinoma, with patients selected by companion diagnostic testing.
This page is based on FDA prescribing information and the EMA medicine record for trastuzumab, cross-checked with the National Cancer Institute dictionary; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
HER2-positive cancers are factories with too many growth antennas on their roof, catching every signal to multiply. Trastuzumab is a flag planted on each antenna. The flags both jam the growth signal and call in the immune system's demolition crew, which recognises the flags and tears the factory down.
In simple terms
Trastuzumab is a recombinant humanized antibody given by infusion that binds HER2, a growth receptor found in excess on certain breast and stomach cancer cells. After binding, it induces antibody-dependent cell-mediated cytotoxicity against tumour cells that overexpress HER2, helping the immune system destroy them, and it also interferes with growth signalling. Only patients whose tumours overexpress HER2, identified by companion diagnostic testing, receive the drug.
In depth
Trastuzumab is a recombinant humanized monoclonal antibody directed against the human epidermal growth factor receptor 2 (HER2). After binding to HER2 on the tumour cell surface, trastuzumab induces antibody-dependent cell-mediated cytotoxicity against tumour cells that overexpress HER2, and it also inhibits HER2-mediated signalling. HER2 is overexpressed by many adenocarcinomas, particularly breast adenocarcinomas, which is why patient selection relies on an FDA-approved companion diagnostic or equivalent HER2 testing.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
How HER2 antibodies work
- Some tumor cells overexpress HER2, a receptor that drives constant growth signaling.
- The antibody binds an extracellular region of HER2 on the tumor cell (pertuzumab blocks its dimerization domain).
- HER2-driven growth signaling is reduced.
- The antibody also flags the tumor cell for immune cells, which then destroy it.
Target: Human epidermal growth factor receptor 2 (HER2)
A growth receptor overexpressed by many adenocarcinomas, particularly breast cancers; marking it flags the cancer cells for immune destruction and blocks growth signalling.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in United States
FDA- For the adjuvant treatment of adults with HER2-overexpressing node-positive or node-negative breast cancer, as part of a treatment regimen consisting of doxorubicin, cyclophosphamide, and either paclitaxel or docetaxel, as part of a treatment regimen with docetaxel and carboplatin, or as a single agent following multi-modality anthracycline-based therapy, with patients selected by an FDA-approved companion diagnostic
- In combination with paclitaxel, for first-line treatment of adults with HER2-overexpressing metastatic breast cancer, and as a single agent for adults with HER2-overexpressing breast cancer who have received one or more chemotherapy regimens for metastatic disease
- In combination with cisplatin and capecitabine or 5-fluorouracil, for the treatment of adults with HER2-overexpressing metastatic gastric or gastroesophageal junction adenocarcinoma
Approved uses in European Union
EMA- As monotherapy, for patients with HER2-positive metastatic breast cancer who have received at least two chemotherapy regimens for their metastatic disease, where prior chemotherapy must have included at least an anthracycline and a taxane unless patients are unsuitable, and hormone-receptor-positive patients must also have failed hormonal therapy unless unsuitable
- In combination with paclitaxel, for patients with HER2-positive metastatic breast cancer who have not received chemotherapy for their metastatic disease and for whom an anthracycline is not suitable
- In combination with docetaxel, for patients with HER2-positive metastatic breast cancer who have not received chemotherapy for their metastatic disease
- In combination with an aromatase inhibitor, for postmenopausal patients with hormone-receptor-positive HER2-positive metastatic breast cancer not previously treated with trastuzumab
- For patients with HER2-positive early breast cancer following surgery, chemotherapy (neoadjuvant or adjuvant), and radiotherapy (if applicable); following adjuvant chemotherapy with doxorubicin and cyclophosphamide in combination with paclitaxel or docetaxel; in combination with adjuvant chemotherapy consisting of docetaxel and carboplatin; or in combination with neoadjuvant chemotherapy followed by adjuvant trastuzumab therapy for locally advanced (including inflammatory) disease or tumours greater than 2 cm in diameter
Official sources
The statements on this page trace back to these records.
- Herceptin (trastuzumab) — Summary of product characteristics and package leaflet, English version
European Medicines Agency
- U.S. Food and Drug Administration: trastuzumab prescribing information
U.S. Food and Drug Administration
- National Cancer Institute: trastuzumab
National Cancer Institute
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.