ATLANTA -- A new experimental drug delayed the growth of advanced breast cancer in women who had stopped responding to the drug Herceptin and were out of treatment options, doctors reported Saturday.
The experimental drug, Tykerb, worked so well that an international study of it was stopped early, in April, based on results in 321 women.
Those who received Tykerb plus the chemotherapy drug Xeloda had no growth of their tumors for 8 1/2 months. That compares to 4 1/2 months for those given only Xeloda, said Dr. Charles Geyer Jr. of Allegheny General Hospital in Pittsburgh.
He led the study and reported results Saturday at a meeting in Atlanta of the American Society of Clinical Oncology.
Tykerb's manufacturer, British-based GlaxoSmithKline, said it would expand global access to the drug under compassionate use provisions, and would seek approval to sell it in the United States and elsewhere later this year.
"This is huge," said Dr. Roy Herbst, a cancer specialist at the University of Texas' M.D. Anderson Cancer Center in Houston, who had no role in the study but has consulted for Glaxo in the past. "The next step will be to use it in patients instead of Herceptin up front," to see whether it is more effective, he said.
Herceptin and Tykerb are members 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 breast cancer, but eventually it stops working and women succumb to the disease.
Tykerb works in a similar yet completely novel way. Like Herceptin, it targets a protein called HER-2/neu, which is made in abnormally large quantities in roughly one-fourth of all breast cancers. Herceptin blocks the protein on the cell's surface; Tykerb does it inside the cell, and blocks a second abnormal protein, too.
In the study, Tykerb also showed signs of being able to prevent cancer from spreading to the brain. That happened to four of the 161 women given Tykerb and Xeloda, compared to 16 of the 160 women given Xeloda alone.
About 14 percent of women on the Tykerb-Xeloda combination and 11 percent on Xeloda alone stopped treatment because of side effects. Diarrhea and rash were more common in those who received Tykerb.
No patients developed heart failure, but four of the 161 on the drug combination had a modest decrease in pumping power of the main chamber of the heart -- side effects that also have been seen with Herceptin.
Tykerb has one big advantage over Herceptin -- it's a pill instead of an intravenous drug, which should make it cheaper and easier to use, doctors said.
Studies are in the works to test it in combination with Herceptin as well as other breast cancer drugs.
Breast cancer is the most common major cancer in American women and the second leading cause of cancer deaths in women. About 213,000 new cases are expected to occur in the United States this year and more than 1 million worldwide.
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