Enhertu Approved in England for HER2-Low Metastatic Breast Cancer: What Patients Need to Know

England's NHS has opened access to Enhertu (trastuzumab deruxtecan) for eligible patients with HER2-low advanced or metastatic breast cancer — a significant development in precision cancer treatment.

The decision by the UK's National Institute for Health and Care Excellence (NICE) follows evidence from clinical trials showing that Enhertu can extend both progression-free survival and overall survival compared with conventional chemotherapy.

Around 1,000 people a year in England are expected to become eligible for the treatment.

What is Enhertu?

Enhertu, whose generic name is trastuzumab deruxtecan, is an antibody-drug conjugate (ADC) developed by AstraZeneca and Daiichi Sankyo.

It combines an antibody that targets HER2 with a powerful chemotherapy payload.

The antibody binds to HER2 on cancer cells and helps deliver the cytotoxic drug to the tumour. This approach allows trastuzumab deruxtecan to work against cancers expressing relatively low levels of HER2.

What does HER2-low mean?

HER2 is a protein found on the surface of breast cancer cells.

Traditionally, breast cancers were broadly divided into HER2-positive and HER2-negative disease.

However, research has shown that some cancers classified as HER2-negative actually express low levels of HER2.

HER2-low generally refers to:

HER2 IHC 1+, or

HER2 IHC 2+ with a negative ISH test.

These cancers were historically managed as HER2-negative breast cancers.

The emergence of trastuzumab deruxtecan has made this biological distinction clinically important because it provides a targeted treatment option for eligible patients with HER2-low metastatic disease.

What did the clinical trial show?

One of the major studies supporting Enhertu is the DESTINY-Breast04 phase 3 clinical trial, involving 557 patients with HER2-low metastatic breast cancer.

The trial compared trastuzumab deruxtecan with physician's-choice chemotherapy.

Progression-free survival

Patients receiving Enhertu had a median progression-free survival of:

9.9 months

compared with:

5.1 months

for physician's-choice chemotherapy.

The hazard ratio for disease progression or death was approximately 0.50.

Overall survival

Median overall survival was:

23.4 months with Enhertu

versus

16.8 months with chemotherapy.

That represents approximately 6.6 additional months in median overall survival in the overall trial population.

The study therefore demonstrated statistically significant improvements in both progression-free and overall survival.

Who can receive Enhertu under the NHS recommendation?

The NICE recommendation applies to adults with HER2-low unresectable or metastatic breast cancer who have:

previously received chemotherapy in the metastatic setting; or

experienced recurrence during adjuvant chemotherapy or within 6 months of completing adjuvant chemotherapy.

The treatment is given as trastuzumab deruxtecan monotherapy within its licensed indication.

This does not mean every person with HER2-low breast cancer automatically qualifies. Individual treatment decisions depend on tumour characteristics, previous treatment, disease progression and clinical assessment.

Why is the 2026 decision significant?

The story is unusual because NICE previously rejected routine NHS funding for this indication in 2024.

The earlier decision did not conclude that Enhertu lacked clinical benefit.

Instead, NICE concluded that the medicine's estimated cost-effectiveness was above the range it considered an acceptable use of NHS resources at the price proposed at that time.

In 2026, the situation changed.

NICE's cost-effectiveness framework was updated, including a higher threshold for evaluating medicines, while a new commercial agreement was reached with the manufacturers.

These changes allowed NICE to recommend Enhertu for NHS use in England.

What are the important side effects?

Enhertu is a powerful anticancer medicine and can cause significant adverse effects.

Reported adverse effects include:

nausea

fatigue

vomiting

reduced blood-cell counts

hair loss

other chemotherapy-related toxicities.

One particularly important adverse effect is interstitial lung disease (ILD) or pneumonitis.

In DESTINY-Breast04, drug-related ILD/pneumonitis occurred in approximately 12.1% of patients, with fatal events occurring in 0.8%.

Patients receiving trastuzumab deruxtecan therefore require appropriate clinical monitoring.

New or worsening respiratory symptoms such as cough or shortness of breath should be assessed promptly by the treating oncology team.

Why this matters for precision medicine

The Enhertu story demonstrates how cancer treatment is becoming increasingly driven by tumour biology and biomarkers.

Rather than treating all breast cancers in the same way, clinicians increasingly use information such as:

HER2 expression

hormone-receptor status

BRCA mutations

PIK3CA mutations

ESR1 mutations

PD-L1 expression

other molecular characteristics.

The goal is to identify treatments that are more specifically suited to the biological characteristics of an individual's cancer.

What does this mean for patients outside England?

The NHS decision applies specifically to England.

Scotland had already made Enhertu available for this indication, while manufacturers have said they will seek access decisions from health authorities in Wales and Northern Ireland.

For countries such as Nigeria, an NHS recommendation should not automatically be interpreted as a Nigerian treatment recommendation.

Local regulatory approval, oncology guidelines, availability of HER2 testing, medicine cost, reimbursement and health-economic considerations all need to be evaluated separately.

The bigger picture

Enhertu's journey from an initial NICE rejection to NHS access highlights an important reality in modern oncology:

Clinical effectiveness is only one part of medicine access.

Drug pricing, health-technology assessment, healthcare budgets, commercial agreements and treatment infrastructure can all influence whether a medicine becomes routinely available.

For patients with HER2-low metastatic breast cancer in England, however, the 2026 decision means an additional targeted treatment option is now available through the NHS.

Key takeaway

Enhertu (trastuzumab deruxtecan) has been recommended for eligible adults in England with HER2-low advanced or metastatic breast cancer following prior chemotherapy or qualifying recurrence.

Clinical evidence from DESTINY-Breast04 showed longer progression-free and overall survival compared with physician's-choice chemotherapy.

The development represents an important milestone in the use of antibody-drug conjugates and biomarker-guided cancer treatment.

Patients should discuss HER2 testing and treatment options with their oncologist rather than assuming that a HER2-low result alone means Enhertu is appropriate.