FDA clears Pfizer Tukysa with trastuzumab and pertuzumab for HER2 maintenance

Pfizer said the Food and Drug Administration approved Tukysa (tucatinib) with trastuzumab and pertuzumab as maintenance therapy for adults with unresectable locally advanced or metastatic HER2-positive breast cancer after induction treatment.

What the agency cleared

On Oct. 7, 2026, the Food and Drug Administration approved tucatinib — sold as Tukysa by Seagen, a Pfizer subsidiary — in combination with trastuzumab and pertuzumab for the maintenance treatment of adults with unresectable locally advanced or metastatic HER2-positive breast cancer following induction treatment. The agency's notice and Pfizer's release the same day describe the same indication and the same pivotal trial.

Pfizer frames the decision as moving Tukysa into an earlier, front-line maintenance setting and as a chemotherapy-free option meant to delay progression after induction. Tukysa was already cleared with trastuzumab and capecitabine for later-line HER2-positive metastatic disease, including patients with brain metastases.

How HER2CLIMB-05 was built

Approval rests on HER2CLIMB-05 (NCT05132582), a randomized, double-blind, placebo-controlled Phase 3 study in 654 adults. Eligible patients had HER2-positive unresectable locally advanced or metastatic breast cancer, with or without brain metastases, and no investigator-assessed progression after four to eight cycles of trastuzumab, pertuzumab, and a taxane.

Patients received tucatinib 300 mg or placebo orally twice daily with trastuzumab and pertuzumab given intravenously, or with a fixed-dose subcutaneous combination of trastuzumab, pertuzumab, and hyaluronidase. Patients with hormone receptor–positive disease could continue endocrine therapy. Treatment continued until progression or unacceptable toxicity. Pfizer says 326 patients were randomized to the Tukysa arm and 328 to placebo.

The progression-free survival gap

The primary endpoint was investigator-assessed progression-free survival under RECIST v1.1. Median progression-free survival was 24.9 months (95% confidence interval 21.3 to not reached) with tucatinib versus 16.3 months (95% confidence interval 12.6 to 18.7) with placebo, for a hazard ratio of 0.64 (95% confidence interval 0.51 to 0.80; p<0.0001). Pfizer describes that as a 35.9% reduction in the risk of progression or death and as 8.6 more months without the cancer worsening. Overall survival was not mature at the progression-free survival analysis, the agency said.

The recommended tucatinib dose is 300 mg orally twice daily with trastuzumab and pertuzumab until progression or unacceptable toxicity.

Safety the label puts first

The Food and Drug Administration's notice flags a boxed warning for hepatotoxicity and warnings for diarrhea, embryo-fetal toxicity, and higher serum creatinine without a change in renal function. Pfizer says safety was generally consistent with Tukysa's known profile except for more severe hepatotoxicity, and that most of those liver events were asymptomatic and reversible with dose changes or stopping the drug.

Common adverse reactions in at least 20% of patients on the Tukysa regimen, Pfizer says, were diarrhea, musculoskeletal pain, hepatotoxicity, nausea, fatigue, rash, and vomiting. Serious adverse reactions in at least 1% included hepatotoxicity (3.9%), including one fatal drug-induced liver injury.

What the approval does not settle

List price, payer coverage, and any change to Pfizer's financial guidance were not in Wednesday's materials. Overall survival remains immature, and real-world use will still turn on how clinics manage the liver-monitoring rules and diarrhea risk the label emphasizes — none of which the approval notice settles.