NEW YORK — October 7, 2026
Pfizer Inc. (NYSE: PFE) announced that the U.S. Food and Drug Administration (FDA) has approved TUKYSA® (tucatinib) in combination with trastuzumab and pertuzumab for the maintenance treatment of adults with unresectable locally advanced or metastatic HER2-positive (HER2+) breast cancer following induction treatment. The approval expands TUKYSA’s use into the front-line maintenance setting, providing a chemotherapy-free option intended to delay disease progression after initial treatment. The decision is supported by results from the pivotal Phase 3 HER2CLIMB-05 trial.
Phase 3 Trial Demonstrates Longer Progression-Free Survival
In HER2CLIMB-05, the TUKYSA combination reduced the risk of disease progression or death by 35.9% compared with placebo plus trastuzumab and pertuzumab. Median progression-free survival (PFS) was 24.9 months in the TUKYSA group versus 16.3 months in the placebo group, representing an improvement of 8.6 months. The primary endpoint was met with a hazard ratio of 0.64 and a p-value below 0.0001. The randomized, double-blind trial enrolled 654 patients who had completed induction treatment with trastuzumab, pertuzumab and a taxane without disease progression.
Safety Findings Highlight Liver-Related Risks
The safety profile was generally consistent with the known effects of TUKYSA, although increased severity of hepatotoxicity was observed. Most reported liver-related events were described as generally asymptomatic and reversible with dose modification or treatment discontinuation. The most common adverse reactions included diarrhea, musculoskeletal pain, hepatotoxicity, nausea, fatigue, rash and vomiting. One patient experienced a fatal adverse reaction of drug-induced liver injury. TUKYSA carries a boxed warning for severe and potentially fatal hepatotoxicity, and the prescribing information calls for liver function testing before treatment and regular monitoring during therapy. Diarrhea can also be severe and may require treatment interruption, dose reduction or discontinuation
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Approval Expands Pfizer’s HER2-Positive Breast Cancer Strategy
TUKYSA is an oral HER2 tyrosine kinase inhibitor that targets HER2 signaling. The newly approved combination offers a maintenance approach after induction therapy, potentially allowing patients to continue HER2-directed treatment without ongoing chemotherapy. TUKYSA was previously approved in combination with trastuzumab and capecitabine for adults with advanced unresectable or metastatic HER2-positive breast cancer, including certain patients with brain metastases who have received prior anti-HER2 treatment. Pfizer said the latest approval strengthens its breast cancer portfolio and expands treatment options across different stages of the metastatic disease journey. Overall survival remains a key secondary endpoint in HER2CLIMB-05.
Source::Pfizer, press release
