FDA approves Pfizer's Tukysa as first-line maintenance for HER2-positive metastatic breast cancer

The US Food and Drug Administration has approved Pfizer’s Tukysa (tucatinib) together with trastuzumab and pertuzumab as maintenance treatment for adults with advanced or metastatic HER2-positive breast cancer who have completed initial (induction) therapy, Pfizer announced on 7 October 2026.

The evidence

• The approval is based on HER2CLIMB-05, a randomised, double-blind, placebo-controlled phase 3 trial published in the Journal of Clinical Oncology.
• After induction with trastuzumab, pertuzumab and a taxane, 326 patients received tucatinib plus the two antibodies and 328 received placebo plus the antibodies.
• Median progression-free survival was 24.9 months with tucatinib versus 16.3 months with placebo (hazard ratio 0.64).

Safety and limitations

• The label has a boxed warning for severe liver toxicity. Serious liver toxicity occurred in 3.9% of patients, including one death from drug-induced liver injury; liver tests are required before and during treatment.
• Common side effects included diarrhoea, nausea, fatigue, rash and vomiting.
• Overall survival results are not yet available, and progression was assessed by investigators.
• “Chemotherapy-free” applies only to the maintenance phase; patients first received chemotherapy.

Tukysa was first approved in 2020 for later-line use. Patients should discuss whether this option suits them with their oncologist.