Pfizer Inc. announced positive topline results from its Phase 3 HER2CLIMB-05 trial, marking a potential breakthrough in first-line treatment for patients with HER2-positive (HER2+) metastatic breast cancer (MBC).
The study evaluated the addition of the tyrosine kinase inhibitor TUKYSA® (tucatinib) to the standard maintenance therapy of trastuzumab and pertuzumab, following induction chemotherapy. The combination demonstrated a statistically significant and clinically meaningful improvement in progression-free survival (PFS) compared to standard therapy alone, meeting the trial’s primary endpoint.
“HER2+ breast cancer remains a difficult subtype to manage, with most patients experiencing progression even with current first-line therapies,” said Dr. Erika Hamilton, principal investigator of the trial and Director of Breast Cancer Research at the Sarah Cannon Research Institute. “These results suggest TUKYSA may help delay disease progression or death in more patients, while maintaining a manageable safety profile.”
HER2 is overexpressed in roughly 15–20% of breast cancer cases and is linked to poorer outcomes. Despite effective first-line therapies, many patients see their disease worsen within two years. Pfizer sees TUKYSA’s performance in HER2CLIMB-05 as a step toward changing that trajectory.
“We see a real opportunity to move toward a chemotherapy-free maintenance approach in the front-line setting,” said Dr. Johanna Bendell, Chief Development Officer, Oncology at Pfizer. “These results support TUKYSA’s potential role earlier in treatment, especially given its established safety profile.”
Currently, TUKYSA is approved in over 50 countries, including the U.S., where it’s indicated for third-line use in HER2+ MBC patients. It is not yet approved for first-line treatment. Pfizer plans to present full HER2CLIMB-05 results at an upcoming medical congress and will engage with regulatory agencies on potential label expansion.
The company emphasized its commitment to advancing care for HER2+ MBC, a cancer subtype with a five-year survival rate as low as 41%–47%.