STAT+: Pfizer's blockbuster Ibrance slows tumor progression in another type of breast cancer

Pfizer said Thursday its drug Ibrance showed efficacy in a group of breast cancer patients who do not currently have access to the medicine, potentially expanding its use.

Ibrance, which generates annual sales of $4.3 billion, is currently used for patients whose tumors are positive for the estrogen receptor (ER) and negative for a second biomarker, called HER2. That population represents 70% of women with breast cancer. But the new results are in patients whose tumors test positive for both the estrogen receptor and HER2, a population that  represents 10% of breast cancer patients.

Although not a game changer for Pfizer, the data could help cushion Ibrance’s losses of market share to Kisqali, a similar drug from Novartis. Kisqali has shown to improve survival in advanced breast cancer; Ibrance has not. While early data had indicated a medicine like Ibrance, known as a CDK 4/6 inhibitor, should work in HER2+ patients, this is the first data showing that to be the case. This could result in increased use of Ibrance in this group.

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