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.

Breast cancer is the second leading cause of cancer-related death among women, after lung cancer. This year, an estimated 226,870 women will be diagnosed with breast cancer - about 40,000 of them with advanced breast cancer - and 39,510 will die from the disease.

A late-stage trial of 724 women showed those who received Afinitor plus Aromasin on average had 7.8 months before their cancer worsened, a 4.6 month improvement over people getting just Aromasin plus a placebo, the FDA said.

Cancer is an increasingly important therapeutic area for Novartis, which faces stiff competition in the field from cross-town rival Roche Holding AG, the world leader in oncology.

"This approval redefines the treatment and management of advanced hormone receptor-positive breast cancer, offering a critical new option for physicians and patients," said the co-lead investigator for the main Afinitor trial, Dr. Gabriel Hortobagyi, who is also a consultant for Novartis and chairman of Breast Medical Oncology at the University of Texas MD Anderson Cancer Center.

(Reporting By Toni Clarke in Boston; additional reporting by Anna Yukhananov in Washington; editing by Carol Bishopric and Andre Grenon)

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