Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.
Trastuzumab is a biologic medicine, a monoclonal antibody that binds HER2, a growth-signal receptor that some cancers make in large amounts, and flags those cells for the immune system. Given by drip or injection, it is used for HER2-positive breast cancer and HER2-positive stomach cancer. It is sold as Herceptin and as biosimilars.
Whether trastuzumab works depends on the tumour: it is used only when tests on the cancer tissue show high HER2 (ERBB2) levels, which arise in the tumour and are not part of the DNA a person was born with. For inherited genes, studies have looked at the antibody receptors FCGR2A and FCGR3A and at a common ERBB2 variant (I655V) linked in some studies to heart side effects. The findings are weak, and there is no CPIC or DPWG guideline.
Every published finding on gene variants and Trastuzumab. Upload your DNA file to see which of these rows apply to you.
PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.
FCGR3A rs396991: Level 3. Efficacy: Breast Neoplasms. 2.
FCGR2A rs1801274: Level 3. Efficacy: Breast Neoplasms. 2.
ERBB2 rs1136201: Level 3. Toxicity: Breast Neoplasms, Drug Toxicity. 1.
BARD1 rs2070096: Level 3. Efficacy: Breast Neoplasms. 1.
Studies of how well it worked in people carrying a variant.
Studies of side effects in people carrying a variant.
ERBB2 rs1136201: Allele G is associated with response to trastuzumab.
Study findings and evidence levels: PharmGKB (CC BY-SA 4.0). Guidelines: CPIC and DPWG, as bundled in PharmCAT. Most studies were done mainly in people of European ancestry.
More drugs from the same category
Not a prescribing recommendation. This page is educational information about pharmacogenomic research and clinical guidelines - it is not medical or dosing advice, and not a prediction of how any medication will work for you. Never start, stop, or change a medication or dose based on it; talk to your doctor or pharmacist, who can order clinical-grade testing if appropriate.
Content updated September 2026.
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