Pfizer's TUKYSA Extends Progression-Free Survival by Over 8 Months in HER2+ Metastatic Breast Cancer

Pfizer Inc. has released detailed findings from its Phase 3 HER2CLIMB-05 study, evaluating TUKYSA® (tucatinib) as part of an investigational first-line maintenance therapy combination following chemotherapy for patients with HER2-positive metastatic breast cancer (MBC). The study's primary endpoint analysis demonstrated that the combination of TUKYSA, trastuzumab, and pertuzumab reduced the risk of disease progression or death by 35.9% compared to a regimen of placebo, trastuzumab, and pertuzumab.

The trial found that the median progression-free survival (PFS) was 24.9 months in the TUKYSA arm, compared to 16.3 months in the placebo arm. This represents an extension of median PFS by 8.6 months. The benefit was observed across various pre-specified patient subgroups, including those with or without a history of brain metastases.

While overall survival data was not yet mature for analysis, the study indicated a numerical trend towards improvement with the addition of TUKYSA. The safety profile of the TUKYSA combination was generally consistent with the known safety profiles of the individual therapies, with diarrhea, hepatic events, and nausea being the most common adverse events.

These results have been published in the Journal of Clinical Oncology. Pfizer plans to discuss these findings with regulatory authorities, as TUKYSA is not currently approved for first-line treatment. The drug is approved in more than 50 countries for later-line treatment of HER2+ MBC.