Adding Tukysa to First Treatments Delays Growth of Metastatic HER2-Positive Breast Cancer

The standard first treatment people receive for metastatic HER2-positive breast cancer is taxane chemotherapy, along with two anti-HER2 medicines: Herceptin (chemical name: trastuzumab) and Perjeta (chemical name: pertuzumab). This is called induction therapy by doctors. After this  therapy is completed, people receive maintenance therapy — Herceptin and Perjeta — for as long as it’s effective.

Results from the HER2CLIMB-05 trial show that adding Tukysa (chemical name: tucatinib) to maintenance therapy controls cancer growth better than Herceptin and Perjeta alone. 

The research was presented at the 2025 San Antonio Breast Cancer Symposium and published at the same time in The Journal of Clinical Oncology.

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  Progression-free survival — how long people lived without the cancer growing — was about 25 months for people who received Tukysa, Herceptin, and Perjeta maintenance therapy compared to about 16 months for people who received only Herceptin and Perjeta.

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  The addition of Tukysa offered benefits regardless of the cancer’s hormone receptor status or whether it had spread to the brain.

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  Overall survival — how long people lived whether or not the cancer grew — appeared to be better for people who received Tukysa, but longer follow-up is needed.

If metastatic HER2-positive breast cancer grows during maintenance therapy, the next treatment is almost always chemotherapy. 

“The results of HER2CLIMB-05 show that the addition of tucatinib to the standard of care represents an enhanced first-line maintenance therapy option for patients with HER2-positive metastatic breast cancer,” Erika Hamilton, MD, director of breast cancer research at the Sarah Cannon Research Institute, explained during a media briefing on the study. “[This provides] an opportunity to prolong time to disease progression and time off chemotherapy.”

Five-year relative survival rates for metastatic HER2-positive breast cancer range from 41% to 47%. Researchers are working to find more effective treatments for metastatic HER2-positive disease, especially treatments that aren’t chemotherapy.

The study included 654 people with metastatic HER2-positive breast cancer who had completed four to eight cycles of induction chemotherapy plus Herceptin and Perjeta without the cancer growing.

People were randomly assigned to receive one of two maintenance regimens:

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  326 people received Tukysa along with continued Herceptin and Perjeta

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  328 people received a placebo — a pill that looked just like Tukysa but contained no medicine – along with Herceptin and Perjeta

Half the people were followed for less than 23 months and half were followed for longer periods of time.

Overall, progression-free survival was nearly nine months longer for people who received Tukysa (24.9 months vs. 16.3 months).

For people with HER2-positive hormone receptor-negative breast cancer, progression-free survival was 24.9 months for people who received Tukysa and 12.6 months for people who received placebo — a difference of 12.3 months.

For people with HER2-positive hormone receptor-positive breast cancer, progression-free survival was 25 months for people who received Tukysa and 18.1 months for people who received placebo, a difference of 6.9 months.

Among the people with brain metastases, adding Tukysa nearly doubled the time until the brain metastases grew — from 4.3 months to 8.5 months.

At the time the data were analyzed, overall survival couldn’t be calculated. But fewer people who received Tukysa had died than people who had received placebo (18 vs. 33).

According to Hamilton, the results suggest that Tukysa may offer benefits to people no matter their age or the hormonal status of the cancer. She emphasized how important it is to better target the HER2 protein and control the cancer during maintenance therapy, rather than waiting for the cancer to grow.

She noted that the results of the HER2CLIMB-05 trial, along with findings from the PATINA trial, support a shift toward more personalized treatment for people with metastatic disease. The PATINA trial showed that adding Ibrance (chemical name: palbociclib) to the maintenance regimen for metastatic triple-positive breast cancer stopped cancer growth for more than a year.