Pfizer’s drug Tukysa, given as an initial treatment for an advanced form of breast cancer, slowed tumor growth by more than eight months, according to a study that could expand its use.
Patients who received Tukysa in addition to standard treatment for metastatic disease went more than two years without their cancer progressing, compared with 16.3 months for those who received traditional treatment.
The drug increased the risk of side effects, particularly liver complications and diarrhea, with 14% of patients dropping out of the study and one treatment-related death.
The study, funded by Pfizer, is presented at the San Antonio Breast Cancer Symposium and simultaneously published in the Journal of Clinical Oncology.
Tukysa is approved for advanced breast cancer stimulated by a protein called human epidermal growth factor receptor 2, or HER2, given after the tumor stops responding to drugs such as Herceptin and Perjeta from Roche Holding AG. The results of the new study suggest it should be added to initial treatment for the disease, which accounts for about one in five breast cancers, the researchers said.
Giving it earlier offers an improved treatment option for patients, extending the time until the disease progresses and helping extend their time off chemotherapy, says Erika Hamilton, director of breast cancer research at the Sarah Cannon Research Institute in Nashville, who led the study.
Pfizer plans to discuss the study with regulatory authorities. The results could also boost sales of the drug, which generated around 480 million US dollars (around 2.174 billion reais) in 2024.
A secondary analysis also suggested that administering the new regimen early, rather than using Tukysa later after disease progression, could allow patients to stay alive longer. However, more data is needed.
Pfizer “is committed to advancing treatment options that significantly improve the lives of people with metastatic breast cancer,” Jeff Legos, director of oncology, said in a statement.
The prognosis for HER2+ breast cancer has improved considerably in recent years thanks to new treatments. AstraZeneca’s drug Enhertu, for example, slowed the progression of HER2+ breast cancer by more than a year in a recent study. However, the diet causes side effects, including lung inflammation, which can be serious.
Meanwhile, many patients are still waiting for better options. Even with treatment, many women with HER2+ metastatic breast cancer experience progression within two years. Breast cancer remains the most commonly diagnosed cancer among women in the United States.
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