Trastuzumab emtansine
Trastuzumab emtansine (Kadcyla, T-DM1) was the first ADC for a solid tumour (2013). It is still standard after surgery for HER2+ breast cancer patients whose tumour did not fully respond to pre-surgery treatment.
Approved 2013 for pretreated HER2+ metastatic breast cancer (EMILIA) and 2019 for residual disease after neoadjuvant therapy (KATHERINE: invasive DFS HR 0.50, with OS benefit). Non-cleavable linker means no bystander effect, which explains its inferiority to T-DXd in DESTINY-Breast03 and its failure in HER2-low disease. Being displaced post-neoadjuvantly by T-DXd (DESTINY-Breast05).
1.Antibody binds HER2 on the tumour cell surface
- Route
- IV infusion
- Schedule
- 3.6 mg/kg every 3 weeks; 14 cycles in the adjuvant setting
- Dose modifications
- Reduce to 3 then 2.4 mg/kg for thrombocytopenia, hepatotoxicity, neuropathy; discontinue for LVEF <40%
- Monitoring
- LFTs and platelets before each dose; LVEF every 3 months
Source: US prescribing information (DailyMed). Doses are for orientation; the current label governs.
- Medicare
- Part B (clinician-administered)
Given by infusion or injection in a clinic or hospital outpatient department, so it is a Part B drug: Medicare pays 80% after the Part B deductible and the patient owes 20% coinsurance, uncapped in Original Medicare unless a Medigap policy applies. HCPCS J9354.
- Commercial insurance
- covered with prior authorisation
Covered under the medical benefit with prior authorisation confirming diagnosis, biomarker status and line of therapy; site-of-care policies may steer infusions away from hospital outpatient departments.
- Assistance programmes
- Genentech Access Solutions
- Genentech Patient Foundation — Free medicine for eligible patients regardless of insurance type.
- PAN Foundation — Disease-specific co-pay and premium funds; open and closed funds change monthly.
- HealthWell Foundation
- CancerCare Co-Payment Assistance Foundation
- Patient Advocate Foundation Co-Pay Relief
20% Part B coinsurance on a high-cost infusion adds up quickly: Medigap Plan G or N, Medicare Advantage maximum out-of-pocket, Medicaid dual eligibility, or a charity fund are the usual buffers.
Sources: Medicare.gov: Chemotherapy · Medicare.gov: Prescription drugs (outpatient, Part B). Not medical or financial advice; verify with your plan.
- Appraised for
- HER2-positive metastatic breast cancer after trastuzumab and a taxane
- Notes
- Adjuvant use for residual invasive disease after neoadjuvant therapy (KATHERINE) recommended in TA632 (2020).
- NHS England
- Routinely funded for the appraised indication (or via managed access)
Sources: NICE TA458 · SMC advice: trastuzumab emtansine. Funding decisions are indication-specific and change monthly; verify with NICE and your treating team.
- 22 Feb 2013ApprovalUS
HER2+ metastatic breast cancer after trastuzumab and taxane (EMILIA); first ADC for a solid tumour source
- 3 May 2019ApprovalUS
Adjuvant treatment of HER2+ early breast cancer with residual disease (KATHERINE) source
- Q2 2026Label changeUS
Displaced post-neoadjuvantly by T-DXd approval (DESTINY-Breast05) source
Approvals
| Region | Year | Indication |
|---|---|---|
| US | 2013 | HER2+ metastatic breast cancer after trastuzumab and taxane |
| US | 2019 | Adjuvant HER2+ breast cancer with residual disease after neoadjuvant therapy |
| Adverse event | Any grade | Grade 3+ |
|---|---|---|
| Fatigue | 50% | — |
| Nausea | 42% | — |
| Transaminases increased | 32% | — |
| Musculoskeletal pain | 30% | — |
| Haemorrhage | 29% | — |
| Thrombocytopenia | 29% | 6% |
| Headache | 28% | — |
| Peripheral neuropathy | 28% | — |
| Left ventricular dysfunction | 3% | — |
KATHERINE (adjuvant). Rates read from the US prescribing information. Blank cells mean the figure was not sourced, not that it is zero.
| Country | Reimbursement | List price | Assistance |
|---|---|---|---|
| United States | Medicare Part B (physician-administered); commercial plans per formulary | not disclosed | genentech-access.com |
| United Kingdom | NICE: recommended for residual invasive disease after neoadjuvant therapy (TA632) and HER2+ metastatic disease (TA458) | not disclosed | — |
List prices are manufacturer or Medicare figures where publicly disclosed; net prices after rebates are usually lower. Reimbursement changes; check the payer.
Trials
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For HER2-positive metastatic breast cancer that has progressed after trastuzumab and a taxane, trastuzumab deruxtecan is now the standard second-line treatment and T-DM1 has moved later in the sequence. The benefit is large enough that ADC design, not just the target, is understood to be what matters. Patients need lung monitoring because of the risk of pneumonitis.
HER2-positive breast cancer is now routinely treated before surgery so that the pathology result can guide what comes after: patients with no residual cancer continue trastuzumab (with or without pertuzumab), while those with residual disease switch to T-DM1. This model of using the tumour's response as a test has since been copied in triple-negative and other cancers.
Latest papers
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