Pfizer's Tukysa Shows Strong PFS Benefit in First-Line HER2+ Breast Cancer Maintenance at SABCS 2025, Sparking Debate with Enhertu

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Pfizer presented phase III HER2CLIMB-05 trial data at the 2025 San Antonio Breast Cancer Symposium (SABCS), showing Tukysa (tucatinib) plus Herceptin and Perjeta reduced risk of progression or death by 35.9% in first-line maintenance for HER2+ metastatic breast cancer, extending median PFS to 24.9 months vs. 16.3 months125.

Greater efficacy in HR-negative patients (44.6% risk reduction) compared to HR-positive (27.5%), with a trend toward overall survival improvement (46.1% risk reduction)1.

Safety profile manageable; common adverse events included diarrhea, nausea, elevated liver enzymes; Grade 3+ events in 42.3% of Tukysa arm vs. 24.4% control1.

Tukysa positions as potential new first-line option, especially in HR-negative disease, potentially competing with Pfizer's own Enhertu as standard of care12.

Trial enrolled 654 patients post-induction chemotherapy; statistically significant p<0.000112.

Sources:

1. https://european-biotechnology.com/latest-news/pfizer-presents-data-for-tukysa-in-her2-positive-breast-cancer/

2. https://www.oncologypipeline.com/apexonco/sabcs-2025-pfizer-could-battle-itself-first-line-maintenance

5. https://www.fiercepharma.com/pharma/pfizer-tukysa-delays-her2-breast-cancer-progression-first-line-maintenance-therapy