The FDA has approved Pfizer’s Tukysa in combination with trastuzumab and pertuzumab as maintenance treatment for adults with unresectable locally advanced or metastatic HER2-positive breast cancer following induction treatment.
The approval moves Tukysa, or tucatinib, into the front-line maintenance setting, providing a chemotherapy-free regimen after initial treatment.
The decision was supported by the Phase 3 HER2CLIMB-05 trial, which compared Tukysa with placebo, each combined with trastuzumab and pertuzumab. Participants had completed induction treatment with trastuzumab, pertuzumab and a taxane without evidence of disease progression.
The study randomized 326 patients to the Tukysa combination and 328 to the placebo combination. Median investigator-assessed progression-free survival was 24.9 months with Tukysa versus 16.3 months with placebo, a difference of 8.6 months.
The Tukysa regimen reduced the risk of disease progression or death by 35.9%. The reported hazard ratio was 0.64, with a 95% confidence interval of 0.51 to 0.80 and a p-value below 0.0001.
Safety findings were generally consistent with Tukysa’s known profile, except for increased severity of liver toxicity. Most liver toxicity events were asymptomatic and reversible through dose changes or treatment discontinuation.
Common adverse events included diarrhea, musculoskeletal pain, liver toxicity, nausea, fatigue, rash and vomiting. Serious liver toxicity occurred in 3.9% of patients, including one fatal case of drug-induced liver injury.
Progression-free survival was the trial’s primary endpoint; overall survival is a key secondary endpoint. Results were previously published in the Journal of Clinical Oncology and presented at the 2025 San Antonio Breast Cancer Symposium, according to Pfizer.
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