Officials with the FDA have granted accelerated approval to fam-trastuzumab deruxtecan-nxki (Enhertu, Daiichi-Sankyo) for the treatment of adults with unresectable or metastatic HER2-positive breast cancer that have received 2 or more prior anti-HER2-based regimens in the metastatic setting.

Fam-trastuzumab deruxtecan-nxki is a human epidermal growth factor, HER2-directed antibody, and topoisomerase inhibitor conjugate. This means that the new drug is able to target the changes in HER2 that help the cancer grow, divide, and spread, and is linked to a topoisomerase inhibitor, which is a chemical compound that is toxic to cancer cells.

The FDA's approval was based on the results of a clinical trial that enrolled 184 female patients with HER2-positive, unresectable and/or metastatic breast cancer that had received 2 or more prior anti-HER2 therapies in the metastatic setting. The patients in the clinical trial received fam-trastuzumab deruxtecan-nxki every 3 weeks, and tumor imagining was obtained every 6 weeks. The overall response rate was 60.3%, which reflects the percent of patients that had a certain amount of tumor shrinkage with a median duration of response in 14.8 months.

Health care professionals and patients should be advised of the risk of interstitial lung disease and embryo-fetal toxicity, as listed on the Boxed Warning. Reports of interstitial lung disease and pneumonitis have been associated with use of fam-trastuzumab deruxtecan-nxki. The FDA advises health care professionals to tell females of reproductive age, and males with a female partner of reproductive potential, to use effective contraception during treatment with fam-trastuzumab deruxtecan-nxki.

Common adverse effects for patients taking fam-trastuzumab deruxtecan-nxki include nausea, fatigue, vomiting, alopecia, constipation, decreased appetite, anemia, decreased neutrophil count, diarrhea, leukopenia, cough, and decreased platelet count. Patients treated with the drug may be at increased risk of developing left ventricular dysfunction, which occurs when the heart is unable to pump blood effectively to the body.


FDA approves new treatment option for patients with HER2-positive breast cancer who have progressed on available therapies [news release]. Silver Spring, MD; December 20, 2019: FDA. Accessed December 20, 2019.