WASHINGTON - Women with an aggressive form of advanced breast cancer that other treatments have failed to stop gained a new option Tuesday with the approval of a novel drug -- but how much benefit it offers is unclear.
The GlaxoSmithKline PLC drug, Tykerb, is to be taken once daily in pill form and is meant for women who have received prior treatment with the intravenous drug Herceptin and older chemotherapy drugs called taxanes and anthracyclines, the company said. The Food and Drug Administration said it approved Tykerb for use in conjunction with the chemotherapy drug Xeloda.
Glaxo said Tykerb would be available in two weeks. It will cost about US$2,900 a month, the company said.
The initial results of a study reported last year showed that Tykerb in combination with Xeloda delayed tumor growth for an average of 8 1/2 months, or about twice as long as Xeloda alone. Tykerb worked so well that the international study was stopped early and all participants were offered the drug. However, Glaxo said a later analysis of the results of that study showed the delay actually was closer to nearly seven months for women on both drugs, versus almost five months for those on Xeloda alone.
The FDA said it was too early to know if women taking Tykerb and Xeloda would live longer than those taking the latter drug alone.
The lack of that information has left one advocacy group disappointed. Survival -- and not progression of disease -- gives a truer picture of a cancer drug's efficacy, Barbara A. Brenner, the executive director of Breast Cancer Action, told the FDA in a March 5 letter.
"The FDA should not approve drugs that have not shown either a survival benefit or improved quality of life for breast cancer patients with metastatic disease," Brenner's letter read in part.
FDA drugs chief Dr. Steven Galson said Tykerb expanded the options available to women with a type of advanced breast called HER2 positive when it has metastasized, or spread.
"Today's approval is a step forward in making new treatments available for patients who have progression of their breast cancer after treatment with some of the most effective breast cancer therapies available," Galson said.
Tykerb, like Herceptin, is part of a new generation of cancer medicines that more precisely target tumors without killing lots of healthy cells.
Herceptin has been an important option for many women with advanced, HER2 positive breast cancer, but eventually it stops working and women succumb to the disease.
Both drugs target a protein called HER-2/neu, which tumors make in abnormally large quantities in roughly one-fourth of all breast cancers. While Herceptin targets the outside of the HER2 protein, Tykerb works from the inside of the cell.
Because of that difference, Tykerb works in some HER2 positive breast cancers that have been treated with Herceptin but no longer benefit from the older drug, the FDA said.
Generally, women with HER2 positive breast cancer face a greater risk of disease progression and death. Approximately 8,000 to 10,000 women die from metastatic HER2 positive breast cancer each year, the FDA said.
Xeloda, or capecitabine, is made by Switzerland's Roche Holding AG. South San Francisco-based Genentech Inc. makes Herceptin, also known as trastuzumab.
Eventually, Tykerb could be studied for use with Herceptin, said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. And Glaxo said it's studying Tykerb as a treatment for other cancers.
"Some of those reports have been promising and others less so. But it is too early to know which other cancers -- if any -- are going to respond to this new drug," Lichtenfeld said.
Expanded use of Tykerb eventually could make it a blockbuster drug for Glaxo, with annual sales approaching or exceeding $1 billion, analysts have said.
