Fam-trastuzumab deruxtecan-nxki Injection

Enhertu is approved for adults with these HER2-related cancers:

• HER2-positive early breast cancer: before surgery (followed by THP) for Stage II or III disease, or after surgery when residual invasive disease remains.
• HER2-positive metastatic breast cancer: with pertuzumab as first-line treatment, or alone after prior anti-HER2 treatment.
• HER2-low and HER2-ultralow metastatic breast cancer: alone, in specific settings after endocrine therapy or chemotherapy.
• HER2-mutant non-small cell lung cancer: alone, after prior systemic therapy (accelerated approval).
• HER2-positive locally advanced or metastatic gastric or gastroesophageal junction cancer: alone, after a prior trastuzumab-based regimen.
• HER2-positive (IHC 3+) solid tumors: alone, after prior treatment with no satisfactory alternatives (accelerated approval).

Enhertu pairs an antibody that finds HER2 on tumor cells with a cancer-killing chemical called DXd. After the antibody attaches, the cell takes in the drug and releases DXd inside. DXd blocks topoisomerase I, an enzyme cells need to copy DNA, which damages DNA and leads to cell death.

Enhertu is given by IV infusion in a clinic, usually every 3 weeks. It is not given as a push or bolus. Anti-nausea medicine is given first.

• Treatment may be paused, lowered or stopped if side effects occur.
• If a dose is delayed or missed, it is given as soon as possible, and the schedule is adjusted to keep 3 weeks between doses.
• Follow your prescriber's plan.

Common side effects include:

Serious problems include lung inflammation, severe low neutrophil counts with fever, and reduced heart function. Report breathing symptoms or fever right away.

• Lung inflammation (ILD/pneumonitis) can be severe or fatal; symptomatic cases mean permanent discontinuation.
• Severe neutropenia, including febrile neutropenia, can occur; blood counts are checked before each dose.
• Left ventricular dysfunction can occur; heart function is checked before and during treatment, and the drug is stopped for symptomatic heart failure.
• It can cause fetal harm, including problems with amniotic fluid in pregnancy.

The label notes few interaction concerns, but some points matter.

• Do not swap Enhertu with trastuzumab or ado-trastuzumab emtansine; they are not interchangeable.
• Strong CYP3A inhibitors (itraconazole, ritonavir) did not cause meaningful changes in drug levels in studies.
• When used with pertuzumab, follow the prescribed order and schedule.

Not a complete list. The label covers the interactions the manufacturer studied or reported, and our own interaction database does not cover every medicine either. Bring your full medication list, including vitamins and herbal products, to your pharmacist.

• Pregnancy should be ruled out before starting; use effective contraception during treatment and for 7 months afterward (4 months for men with partners who can become pregnant).
• Do not breastfeed during treatment and for 7 months after the last dose.
• Tell your doctor about heart or lung problems.
• People with moderate kidney impairment had more mild-to-moderate lung inflammation; those with moderate liver impairment are monitored for more side effects.
• Not established for children.
• Adults 65 and older had more severe side effects in some studies.

Higher drug exposure was linked to a higher rate of lung inflammation (ILD). At the 6.4 mg/kg dose, the drug did not cause a meaningful lengthening of the QTc interval, a measure of heart rhythm timing.

The antibody and its DXd payload both have a half-life of about 5 to 6 days, which fits dosing every 3 weeks. The antibody is broken down into small peptides and amino acids, and DXd is mainly processed by the CYP3A4 enzyme. Age, sex, weight, race, mild liver impairment, and mild or moderate kidney impairment did not cause meaningful differences in drug levels.

Store vials in a refrigerator at 2°C to 8°C (36°F to 46°F) in the original carton to protect from light until time of reconstitution. Do not freeze.