What is Enhertu, and how does it work?
What are the side effects of Enhertu?
What is the dosage for Enhertu?
What drugs interact with Enhertu?
Is Enhertu safe to use while pregnant or breastfeeding?

What is Enhertu, and how does it work?

Enhertu is a prescription medicine used in adults to treat human epidermal growth factor receptor 2 (HER2)-positive breast cancer that cannot be removed by surgery or that has spread to other parts of your body (metastatic), and who have received two or more prior anti-HER2 breast cancer treatments.

It is not known if Enhertu is safe and effective in children.

What are the side effects of Enhertu?

WARNING

INTERSTITIAL LUNG DISEASE and EMBRYO-FETAL TOXICITY

Interstitial Lung Disease (ILD) and pneumonitis, including fatal cases, have been reported with Enhertu.Monitor for and promptly investigate signs and symptoms including cough, dyspnea, fever, and other new orworsening respiratory symptoms. Permanently discontinue Enhertu in all patients with Grade 2 or higherILD/pneumonitis. Advise patients of the risk and the need to immediately report symptoms.
Embryo-Fetal Toxicity: Exposure to Enhertu during pregnancy can cause embryo-fetal harm. Advise patients of these risks and the need for effective contraception.

Enhertu can cause serious side effects.

The most common side effects of Enhertu include:

nausea
feeling tired
vomiting
hair loss
constipation
decreased appetite
low red blood cell counts
low white blood cell counts
diarrhea
cough
low platelet counts

Enhertu may cause fertility problems in males, which may affect the ability to father children. Talk to your healthcare provider if you have concerns about fertility.

These are not all of the possible side effects of Enhertu. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What is the dosage for Enhertu?

Recommended Dosage And Schedules

Do Not Substitute Enhertu For Or With Trastuzumab Or Ado-Trastuzumab Emtansine

The recommended dosage of Enhertu is 5.4 mg/kg given as an intravenous infusion once every 3 weeks (21-day cycle) until disease progression or unacceptable toxicity.

First Infusion

Administer infusion over 90 minutes.

Subsequent Infusions

Administer over 30 minutes if prior infusions were well tolerated.
Slow or interrupt the infusion rate if the patient develops infusion-related symptoms.
Permanently discontinue Enhertu in case of severe infusion reactions.

Dose Modifications

Management of adverse reactions may require temporary interruption, dose reduction, or treatment discontinuation of Enhertu as described in Tables 1 and 2.

Do Not Re-Escalate The Enhertu Dose After A Dose Reduction Is Made

If a planned dose is delayed or missed, administer as soon as possible; do not wait until the next planned cycle.
Adjust the schedule of administration to maintain a 3-week interval between doses. Administer the infusion at the dose and rate the patient tolerated in the most recent infusion.

Table 1: Dose Reduction Schedule

Dose Reduction Schedule (Starting dose is 5.4 mg/kg.)	Dose to be administered
First dose reduction	4.4 mg/kg
Second dose reduction	3.2 mg/kg
Requirement for further dose reduction	Discontinue treatment

Table 2: Dose Modifications for Adverse Reactions

Adverse Reaction	Severity		Treatment Modification
Interstitial Lung Disease (ILD)/pneumonitis	Asymptomatic ILD/pneumonitis (Grade 1)		Interrupt Enhertu until resolved to Grade 0, then: if resolved in 28 days or less from date of onset, maintain dose. if resolved in greater than 28 days from date of onset, reduce dose one level (see Table 1). consider corticosteroid treatment as soon as ILD/pneumonitis is suspected.
	Symptomatic ILD/pneumonitis (Grade 2 or greater)		Permanently discontinue Enhertu. Promptly initiate corticosteroid treatment as soon as ILD/pneumonitis is suspected.
Neutropenia	Grade 3 (less than 1.0 to 0.5 x 10⁹/L)		Interrupt Enhertu until resolved to Grade 2 or less, then maintain dose.
	Grade 4 (less than 0.5 x 10⁹/L)		Interrupt Enhertu until resolved to Grade 2 or less. Reduce dose by one level (see Table 1).
Febrile Neutropenia	Absolute neutrophil count of less than 1.0 x 10⁹/L and temperature greater than 38.3°C or a sustained temperature of 38°C or greater for more than one hour		Interrupt Enhertu until resolved. Reduce dose by one level (see Table 1).
Left Ventricular Dysfunction	LVEF greater than 45% and absolute decrease from baseline is 10% to 20%		Continue treatment with Enhertu.
	LVEF 40% to 45%	And absolute decrease from baseline is less than 10%	Continue treatment with Enhertu. Repeat LVEF assessment within 3 weeks.
		And absolute decrease from baseline is 10% to 20%	Interrupt Enhertu. Repeat LVEF assessment within 3 weeks. If LVEF has not recovered to within 10% from baseline, permanently discontinue Enhertu. If LVEF recovers to within 10% from baseline, resume treatment with Enhertu at the same dose.
	LVEF less than 40% or absolute decrease from baseline is greater than 20%		Interrupt Enhertu. Repeat LVEF assessment within 3 weeks. If LVEF of less than 40% or absolute decrease from baseline of greater than 20% is confirmed, permanently discontinue Enhertu.
	Symptomatic congestive heart failure (CHF)		Permanently discontinue Enhertu.
Toxicity grades are in accordance with National Cancer Institute Common Terminology Criteria for Adverse Events Version 4.03 (NCI-CTCAE v.4.03).

QUESTION

A lump in the breast is almost always cancer. See Answer

What drugs interact with Enhertu?

No Information Provided

Is Enhertu safe to use while pregnant or breastfeeding?

Based on its mechanism of action, Enhertu can cause fetal harm when administered to a pregnant woman.
There are no available data on the use of Enhertu in pregnant women.
In postmarketing reports, use of a HER2-directed antibody during pregnancy resulted in cases of oligohydramnios manifesting as fatal pulmonary hypoplasia, skeletal abnormalities, and neonatal death.
There is no data regarding the presence of fam-trastuzumab deruxtecan-nxki in human milk, the effects on the breastfed child, or the effects on milk production.
Because of the potential for serious adverse reactions in a breastfed child, women should not breastfeed during treatment with Enhertu and for 7 months after the last dose.