FDA approves new drug for patients with metastatic breast cancer

By Jacqueline Howard, CNN

    (CNN) -- The US Food and Drug Administration has approved the use of the drug tucatinib, or Tukysa, in combination with chemotherapy, for the treatment of adults with advanced forms of HER2-positive breast cancer that either cannot be removed with surgery, or has spread to other parts of the body, including the brain.

"The clinical trial supporting this approval enrolled and specifically studied patients with active brain metastases in addition to the overall population enrolled, which also demonstrated benefit in this subgroup," Dr. Richard Pazdur, director of the FDA's Oncology Center of Excellence, said in a statement Friday.

The FDA granted approval of Tukysa to the company Seattle Genetics, Inc. The drug is approved for patients who have received one or more prior treatments for their cancer, the FDA announced.

HER2-positive breast cancer, which makes up approximately one-fifth of breast cancers, has too much of a protein called human epidermal growth factor receptor 2 (HER2), which promotes the growth of cancer cells. More than 25% of women with metastatic HER2-positive breast cancer will develop brain metastases.

"This approval represents an additional targeted treatment option for patients with HER2-positive breast cancer," Pazdur said in the FDA announcement.

"We recognize that patients with cancer constitute a vulnerable population at risk of contracting the coronavirus disease," Pazdur said. "In this critical time, we remain steadfast in our commitment to patients with cancer and doing everything we can to expedite oncology product development. Tukysa was approved four months prior to the FDA goal date, providing an example of this commitment and showing how our regular work in reviewing treatments for patients with cancer is moving forward without delay."

Previously, a study of 612 patients with advanced HER2-positive metastatic breast cancer published in the New England Journal of Medicine in December, and found that adding the drug tucatinib to a chemotherapy regimen consisting of the drugs trastuzumab and capecitabine could improve survival for those patients.

The patients in the study were randomly assigned to either receive the drug tucatinib or a placebo, and they also received chemotherapy with the drugs trastuzumab and capecitabine.

The researchers found that in the first year of treatment, 33.1% of patients in the tucatinib group did not see their cancer progress compared with 12.3% of patients in the placebo group. The researchers also found that overall survival two years after starting treatment was 44.9% among patients in the tucatinib group and 26.6% among those in the placebo group.

Side effects of the tucatinib treatment that emerged in the study included the risks of diarrhea and elevated levels of an enzyme in the body called aminotransferase.

"Health care professionals should advise patients to notify their health care provider and start antidiarrheals as clinically indicated if diarrhea occurs," the FDA announcement said. "If patients are experiencing severe diarrhea, Tukysa should be interrupted or the dosage reduced. Tukysa can also cause severe hepatotoxicity. Health care professionals should monitor liver tests in patients taking Tukysa every three weeks while the patient is on treatment or as clinically indicated."

The FDA added that women who are pregnant or breastfeeding should not take Tukysa because it may cause harm to a developing fetus or newborn baby.

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