Afinitor Delays Progression of Advanced Breast Cancer

Among postmenopausal women with advanced breast cancer that had become resistant to hormonal therapy, the combination of Afinitor® (everolimus) and Aromasin® (exemestane) delayed cancer progression to a greater extent than Aromasin alone. The results of this Phase III clinical trial were presented at the 2011 European Multidisciplinary Cancer Congress.

Each year roughly 200,000 U.S. women are diagnosed with breast cancer. Many of these breast cancers are hormone receptor-positive, meaning that exposure to estrogen and/or progesterone can cause them to grow.

Treatment of hormone receptor-positive breast cancer often includes hormonal therapies such as tamoxifen or an aromatase inhibitor. Tamoxifen acts by blocking estrogen receptors, and aromatase inhibitors suppress the production of estrogen in postmenopausal women. Aromatase inhibitors include Femara® (letrozole), Arimidex® (anastrozole), and Aromasin® (exemestane). Many women with advanced breast cancer become resistant to hormonal therapy, and treatment options for these women remain limited.

Afinitor is an oral medication that works by inhibiting a protein known as mTOR. The mTOR protein plays an important role in regulating cancer cell division and blood vessel growth. Currently, Afinitor is used for the treatment of selected patients with kidney cancer, pancreatic neuroendocrine tumors, and subependymal giant cell astrocytoma (SEGA).

To explore the use of Afinitor among women with advanced, estrogen receptor-positive, HER2-negative breast cancer, researchers conducted a Phase III clinical trial (BOLERO-2) among 724 women. All of the women had experienced cancer recurrence or progression in spite of treatment with Femara or Arimidex. Study participants were treated with Aromasin alone or in combination with Afinitor.

Survival without cancer progression was 6.9 months among women treated with both Afinitor and Aromasin, compared with 2.8 months among women treated with Aromasin alone.

The U.S. Food and Drug Administration on Friday approved Novartis AG drug Afinitor to treat women with a certain type of breast cancer.

The drug is the first in a class known as mTOR inhibitors to be approved for post-menopausal women with advanced hormone-receptor positive, HER2-negative breast cancer. The European Medicines Agency in June also endorsed Afinitor as a breast cancer treatment.

Afinitor, also known as everolimus, is designed to be given in combination with another drug, Aromasin, to treat women whose cancer has recurred or progressed after treatment with two other therapies. Aromasin is made by Pfizer Inc.

Novartis's drug - expected to become a major seller for the Swiss drugmaker - is already approved to treat patients with four other types of cancer, including kidney and a rare type of pancreatic cancer.

"Afinitor is another example of the value of continuing to study drugs in additional types of cancer after their initial approval," said Dr. Richard Pazdur, head of the FDA's cancer drugs office.