Enhertu (fam-trastuzumab deruxtecan-nxki)
AstraZeneca / Daiichi Sankyo · HER2-Targeted ADC — Topoisomerase I Inhibitor Payload
What is Enhertu? Enhertu (fam-trastuzumab deruxtecan-nxki, T-DXd) is a HER2-targeted ADC by AstraZeneca/Daiichi Sankyo that has transformed treatment for HER2-positive, HER2-low, and HER2-ultralow breast cancer, HER2-positive gastric cancer, and HER2-mutant NSCLC.
About Enhertu
| Brand Name | Enhertu |
| Generic / INN | fam-trastuzumab deruxtecan-nxki |
| Drug Class | HER2-Targeted ADC — Topoisomerase I Inhibitor Payload |
| Manufacturer | AstraZeneca / Daiichi Sankyo |
| Administration | Intravenous (IV) infusion |
| FDA Approval | 2019 |
FDA-Approved Uses
- HER2-positive metastatic breast cancer — after prior trastuzumab
- HER2-low metastatic breast cancer (IHC 1+ or IHC 2+/ISH-)
- HER2-ultralow metastatic breast cancer — HR+
- HER2-positive gastric/GEJ adenocarcinoma — after prior trastuzumab
- HER2-mutant NSCLC — after prior platinum-based chemotherapy
How Does Enhertu Work?
Enhertu delivers DXd (topoisomerase I inhibitor) into HER2-expressing cells. After internalization, DXd causes DNA damage and apoptosis. Its 'bystander effect' kills adjacent tumor cells even with low/no HER2 expression — explaining activity in HER2-low disease.
Dosage & Administration
5.4 mg/kg IV every 3 weeks (breast/NSCLC); 6.4 mg/kg (gastric). First infusion 90 minutes; if tolerated 30–60 minutes subsequently. NOT interchangeable with Kadcyla (T-DM1).
Dosing is individualized by the treating oncologist. Do not adjust without medical guidance. This page is educational only.
Warnings & Side Effects
- ILD/pneumonitis — BOXED WARNING, can be fatal
- Left ventricular dysfunction
- Neutropenia
- NOT interchangeable with Kadcyla (T-DM1)
- Embryo-fetal toxicity
Common Side Effects
- Nausea
- Fatigue
- Alopecia
- Vomiting
- Constipation
- Decreased appetite
- Anemia
- Neutropenia
Storage & Handling
Refrigerate at 2°C to 8°C (36°F to 46°F). Do not freeze.
💰 Medication Cost & Insurance Coverage
Approximate Wholesale Acquisition Cost (WAC / List Price)
~$18,000–$22,000/month
5.4 mg/kg every 3 weeks
Insurance & Prior Authorization
Enhertu requires prior authorization from all major insurance plans. BiologicHealthPlus handles the full PA process — clinical documentation, peer-to-peer reviews, and appeals — at no cost to patients or providers.
Prior Authorization Guide Patient Assistance Insurance & Savings
Frequently Asked Questions — Enhertu
Enhertu is a HER2-targeted ADC delivering a topoisomerase I inhibitor into HER2-expressing cells. It has transformed treatment for HER2-positive AND HER2-low breast cancer.
HER2-low (IHC 1+ or 2+/ISH-) was previously considered HER2-negative. Enhertu is the first approved therapy for HER2-low metastatic breast cancer — representing ~50-60% of all breast cancers.
No — different payload, different dosing, different indications. NOT interchangeable.
ILD/pneumonitis can be fatal. Grade 1 requires dose interruption; Grade 2+ may require permanent discontinuation. Report any new breathing symptoms immediately.
Related Medications & Conditions
Related Medications
Kadcyla (different drug) · Herceptin (trastuzumab) · Perjeta · Keytruda
Related Conditions
HER2-positive breast cancer · HER2-low breast cancer · HER2-positive gastric cancer · HER2-mutant NSCLC