FDA approves tucatinib to keep advanced HER2 breast cancer in check
The FDA on Wednesday approved Pfizer's pill tucatinib, taken with two antibody drugs, as maintenance treatment for advanced HER2-positive breast cancer. In a trial, it kept cancer from growing for about 8.6 months longer than placebo. The label carries a warning about serious liver damage.
The Food and Drug Administration on Wednesday approved a new use for the breast cancer pill tucatinib, sold as Tukysa by Pfizer.
The drug is now approved with two antibody medicines, trastuzumab and pertuzumab, as maintenance treatment. It is for adults with HER2-positive breast cancer that has spread or cannot be removed by surgery, after they finish their first round of treatment. Maintenance treatment aims to keep cancer from growing after it has been brought under control.
HER2 is a protein that drives cancer growth. It is overactive in about 15% to 20% of breast cancers, AJMC reported.
The approval is based on a large trial called HER2CLIMB-05. It enrolled 654 patients who had already finished treatment with trastuzumab, pertuzumab and chemotherapy. Half also took tucatinib, and half took a placebo.
Patients on tucatinib went a median of 24.9 months before their cancer grew, compared with 16.3 months for placebo. That cut the risk of the cancer growing or death by about 36%, OncLive reported. The benefit held whether or not patients had cancer in the brain. It is too early to know whether the drug helps people live longer.
"Today's FDA approval marks the next chapter for [tucatinib], bringing it into the front-line maintenance setting and offering patients a chemotherapy-free option," said Aamir Malik, a Pfizer executive.
There are serious risks. The label has a boxed warning, the FDA's strongest, for severe liver damage. One patient in the trial died of drug-caused liver injury, and 8% stopped the drug because of liver problems. Diarrhea affected 73% of patients. Doctors are told to run liver blood tests every two weeks for the first two months, then every three weeks.
Not every patient will need it. One expert told OncLive that some patients do very well for years on trastuzumab and pertuzumab alone.
Tucatinib was first approved in April 2020 for advanced HER2-positive breast cancer, alongside trastuzumab and the chemotherapy pill capecitabine. The dose is 300 mg by mouth twice a day.
What we know: The FDA approved the three-drug maintenance plan on Oct. 7.
What we don't: Whether adding tucatinib helps patients live longer.
Where outlets agree AJMC and OncLive both report the approval rests on the 654-patient HER2CLIMB-05 trial, which cut the risk of progression or death by about 36%.
Where they differ Supporters call it a chemotherapy-free way to delay progression, but survival data are not yet mature and the drug carries a boxed warning for severe liver damage.