(Correct Herceptin sales period in third paragraph. Story first moved March 13.)

March 13 (Bloomberg) -- GlaxoSmithKline Plc, which plans to introduce five new treatments this year, won U.S. Food and Drug Administration permission to sell Tykerb for breast cancer, the most common cancer among women.

The regulator approved the once-daily pill in combination with Roche Holding AG's Xeloda for treatment of advanced breast cancer in women who carry the HER-2 gene and don't respond to Roche's Herceptin, London-based Glaxo said today in an e-mailed statement. Tykerb belongs to a class of drugs known as dual- kinase inhibitors, which impede the growth of tumor cells.

Tykerb is one of the medicines Glaxo is relying on to help counter slowing growth in sales of its top-selling asthma drug Advair and the loss of patent protection on other products. The company is also seeking a bigger share of the $35 billion global cancer market dominated by Roche and Genentech Inc. The Glaxo pill may rival Herceptin, which is given in monthly infusions and brought in $3.16 billion for Roche last year.

``The data to date is very promising,'' analyst Gbola Amusa of Sanford C. Bernstein in London said in a March 1 telephone interview. ``Oncologists and breast cancer specialists we've spoken to would say these are some of the most promising data sets they have seen.''

A late-stage trial of 324 women given Tykerb and Xeloda found it took 8.4 months until their advanced or metastatic breast cancer progressed, compared with 4.4 months in women given Xeloda alone, a U.S. researcher told the American Society of Clinical Oncology in June.

$1.1 Billion by 2015

Amusa estimated Tykerb will bring in $258 million for Glaxo in the U.S. by 2010 and $1.1 billion by 2015. Glaxo, the world's second largest drugmaker after Pfizer Inc., had sales of 23.23 billion pounds ($45.5 billion) in 2006, about half of which came from the U.S.

Glaxo's American depositary receipts, each representing two ordinary shares, fell 75 cents, or 1.3 percent, to $55.25 at 4:21 p.m. in New York Stock Exchange composite trading.

The drugmaker applied to sell Tykerb in the U.S. in September and was awarded a so-called fast-track review from the FDA in November. An application filed with the European Medicines Agency has been pending since October.

Breast cancer is the most common cancer in women, striking about 1 million women a year worldwide, according to the World Health Organization. An estimated 212,920 new cases of the disease were diagnosed in the U.S. in 2006, according to the American Cancer Society, a patient advocacy group. About 8,000 to 10,000 women die from the HER-2 positive form of breast cancer each year, the FDA said in a statement today. More than 360,000 new cases of breast cancer are diagnosed in Europe every year, Glaxo says.

In a separate statement, Glaxo said it will offer Tykerb for free to low-income Americans without health insurance. Patients enrolled in the Medicare plan for the elderly and disabled may also be eligible if they spend $600 a year on other drugs, Glaxo said.

To contact the reporter on this story: Andrea Gerlin in London agerlin@bloomberg.net

Last Updated: March 14, 2007 04:06 EDT