Novartis drug Afinitor, expected to become a major seller for the Swiss drugmaker, was approved by European regulators to treat women with a certain type of breast cancer, the company said on Monday.

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. American health regulators also backed the drug 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.

Novartis's drug is already approved to treat patients with four other types of cancer, including kidney and a rare type of pancreatic cancer.

"We expect Afinitor to comfortably gain blockbuster status by 2013 and to be an essential pillar for future revenue growth in pharmaceuticals," Kepler Capital Markets analyst Martin Voegtli said. He forecasts $2.2 billion in peak sales of the drug by 2017.