FDA approves tucatinib to maintain control of HER2-positive breast cancer

The Food and Drug Administration approved tucatinib on 7 October 2026 for a new use: keeping advanced HER2-positive breast cancer in check after the first wave of treatment has done its work [s1]. The clearance is recorded as the tenth supplement to the drug's original application, NDA 213411 [s2]. The drug, sold as TUKYSA, is now cleared in combination with trastuzumab and pertuzumab as maintenance treatment for adults with unresectable locally advanced or metastatic HER2-positive breast cancer, given after induction therapy [s1]. It is the third FDA indication for the drug, which was first approved in 2020 [s1].

What maintenance means here

Metastatic HER2-positive breast cancer is usually treated first with an intensive induction phase — trastuzumab and pertuzumab, two antibodies against the HER2 receptor, plus a taxane chemotherapy. When that regimen has brought the disease under control, the question is what to do next to hold the line without the toxicity of continuous chemotherapy. Tucatinib, a small-molecule kinase inhibitor taken as a pill, is now an answer: it is added to the two antibodies once induction is complete, and the chemotherapy is dropped [s1].

The approval rests on HER2CLIMB-05, a randomised, double-blind, placebo-controlled trial that enrolled 654 adults [s1]. To be eligible, patients had to show no evidence of disease progression after four to eight cycles of trastuzumab, pertuzumab and a taxane [s1]. They were then randomised to add either tucatinib 300 mg or placebo twice daily by mouth, continuing the two antibodies — given intravenously, or as a subcutaneous fixed-dose combination with hyaluronidase — until the cancer progressed or the side effects became unacceptable [s1]. The registry listing for the trial is NCT05132582 [s3].

The numbers

The main measure was progression-free survival — the time until the cancer grew or the patient died — as judged by the treating investigator using standard RECIST criteria [s1]. Patients who added tucatinib went a median of 24.9 months before progression or death, against 16.3 months for those who added placebo [s1]. That works out to a hazard ratio of 0.64, with a 95% confidence interval of 0.51 to 0.80 and a p-value below 0.0001 — a roughly one-third reduction in the risk of progression or death over the follow-up, and a result unlikely to be chance [s1].

The recommended dose in this setting is 300 mg taken by mouth twice daily, alongside trastuzumab and pertuzumab [s1].

What to watch

Tucatinib's prescribing information carries a boxed warning — the FDA's strongest — for liver toxicity [s1]. The label also flags diarrhoea, which can be severe; embryo-fetal toxicity, meaning the drug can harm a developing pregnancy; and rises in serum creatinine that reflect how the drug is handled by the kidney rather than actual kidney damage [s1]. These are the signals clinicians monitor during treatment, with blood tests for liver enzymes and attention to any new or worsening diarrhoea.

The approval is specific. It is for HER2-positive disease, confirmed by testing, that is unresectable, locally advanced or metastatic, and it applies to the maintenance setting after induction — not as a first move, and not as a substitute for the induction phase itself [s1]. Tucatinib's two earlier approvals remain distinct: a 2020 clearance with trastuzumab and capecitabine for previously treated HER2-positive metastatic breast cancer, including brain metastases, and a 2023 accelerated approval with trastuzumab for RAS wild-type HER2-positive colorectal cancer [s1].

What the trial does not settle is overall survival — whether people live longer, not just longer without progression — which the progression-free endpoint does not directly measure, and which longer follow-up will have to answer. The benefit shown is real and statistically clear on its own terms; the open question is how it translates over the full course of the disease.

This article is informational and does not constitute medical advice. Decisions about cancer treatment belong with a patient and their oncology team.