FDA approves tucatinib for HER2-positive metastatic breast cancer

The Food and Drug Administration approved the targeted medicine tucatinib (Tukysa) to be used in treatment for people with metastatic HER2-positive breast cancer. The approval includes those with brain metastases. It was announced by tucatinib’s maker Seattle Genetics on April 17.

Tucatinib can now be given with trastuzumab (Herceptin) and capecitabine (Xeloda) to treat people when the cancer has progressed after at least one other line of HER2-targeting therapy given for metastatic breast cancer.

Background

The approval is based on results from the HER2CLIMB trial, presented at the San Antonio Breast Cancer Symposium in December 2019. The randomized, double-blind trial compared tucatinib, trastuzumab, and capecitabine to trastuzumab and capecitabine with a placebo. People in the tucatinib group

• went 2.2 months longer without cancer growing
• lived 4.5 months longer

Tucatinib is a small molecule tyrosine kinase inhibitor, a type of targeted therapy for HER2-positive breast cancer. The HER2CLIMB trial included people with brain metastases to test if the small molecules crossed the blood-brain barrier — a defense in your body that blocks many medicines from reaching the central nervous system. Of people in the study with brain metastases

• 25 percent in the tucatinib group went a year without cancer growing
• 0 people in the placebo group went a year without cancer growing

The main side effects were diarrhea, elevations in certain lab tests, and hand-foot syndrome.

What this means for you

The approval of tucatinib provides a combination of medicines that will be helpful to many people with metastatic HER2-positive breast cancer. When the HER2CLIMB results were announced, doctors were enthusiastic because it suggested people could stay on targeted treatment longer before switching to chemotherapies given by vein and the treatment led to longer overall survival.

Importantly, people with brain metastases are often excluded from clinical trials. That they were included and found to have better outcomes from the addition of tucatinib raises hopes for many in this often-overlooked community.