Trastuzumab Emtansine

What it is and how it works

Trastuzumab emtansine (T-DM1) combines trastuzumab with DM1, a maytansine-derived microtubule inhibitor, via a stable thioether linker. After binding to HER2 and internalisation, lysosomal degradation releases DM1-containing catabolites that disrupt microtubules, causing cell-cycle arrest and apoptosis; the trastuzumab component retains its anti-HER2 actions.

Indications

HER2-positive unresectable locally advanced or metastatic breast cancer previously treated with trastuzumab and a taxane; adjuvant treatment of HER2-positive early breast cancer with residual invasive disease after neoadjuvant taxane- and HER2-targeted therapy.

Dosage and administration (summary)

By intravenous infusion, 3.6 mg/kg every 3 weeks; the first infusion is given over 90 minutes and subsequent infusions over 30 minutes if well tolerated, with dose reductions for toxicity.

Contraindications

Hypersensitivity to trastuzumab emtansine or excipients.

Warnings and precautions

Hepatotoxicity (including rare liver failure and nodular regenerative hyperplasia), thrombocytopenia with haemorrhage, left ventricular dysfunction, interstitial lung disease, peripheral neuropathy and infusion reactions may occur; monitor liver function, platelet count and LVEF. Not interchangeable with trastuzumab or trastuzumab deruxtecan; check product names to avoid medication errors.

Pregnancy

Can cause fetal harm and should not be used in pregnancy; effective contraception is required during and for several months after treatment.

Storage and supply

Store unopened vials refrigerated at 2–8 °C; do not freeze; reconstituted solution may be stored refrigerated for a limited time as stated by the manufacturer.

Source: reference summary prepared from the EU SmPC/EPAR, BNF and WHO Model Formulary. The approved product information in Iran governs.