An experimental drug tested in Pittsburgh is so effective at treating aggressive forms of breast cancer that doctors say it gives new hope to women battling the disease and represents another powerful weapon to attack cancer at its genetic roots. Tykerb -- a so-called "smart drug" that targets only tumor cells -- halts the progress of advanced breast cancer in patients who no longer respond to the best-selling drug Herceptin, according to study results to be presented today at the annual meeting of the American Society of Clinical Oncology in Atlanta. "This is clearly very exciting for breast cancer physicians, and ultimately, it helps us to move in the direction of more personalized cancer therapy," said Dr. Charles Geyer, director of breast oncology at Allegheny General Hospital in the North Side and leader of the international study. Herceptin, manufactured by Calif.-based Genentech, generated a huge buzz in October when researchers announced its extraordinary effectiveness at controlling early-stage breast cancer. Herceptin is effective in about 20 percent of breast cancer cases -- those in which tumors are overloaded with a cancer-causing protein called HER-2, or copies of the gene that makes the protein. Herceptin is an antibody that binds to part of the HER-2 protein to slow or stop its cancer-causing activity. Unlike chemotherapy, the drug leaves healthy cells alone. But Herceptin isn't always the magic bullet, especially in women with advanced breast cancer or tumors that spread elsewhere in the body. About 200,000 women in the U.S. are diagnosed with breast cancer each year, and 40,000 die. The median survival time for women treated for metastatic breast cancer is two years. "Unfortunately, these cancers eventually figure out how to grow around the Herceptin, and at that point our treatment options have been much more limited," Geyer said. Tykerb is a small molecule manufactured by GlaxoSmithKline that binds to HER-2 like Herceptin but also to other members of the same protein family that have been implicated in tumor growth. The drug will give women an option when they no longer receive any benefit from Herceptin and a standard chemotherapy regimen, Geyer said. Another potential benefit of Tykerb is that it can be delivered in a daily pill, while Herceptin is administered through monthly infusions. Tykerb also doesn't appear to have the same adverse side effects as Herceptin, which causes heart failure in 2 to 3 percent of women who take it. "To increase survival for women with advanced breast cancer is absolutely remarkable," said Dr. Victor Vogel, who directs the University of Pittsburgh Cancer Institute Breast Cancer Prevention Program. "It says that (Tykerb) has astonishing efficacy." Carolyn Flavin, 59, of Brookline, was diagnosed with HER-2 breast cancer in September during a routine mammogram. Surgeons removed three tumors from her right breast, and she then underwent eight weeks of chemotherapy. Flavin is taking Herceptin and starting radiation treatments. Despite watching her mother-in-law die of breast cancer 33 years ago, the retired Oliver High School teacher and mother keeps a positive outlook. "It's like Herceptin was made for me, and if Herceptin doesn't work, now there's something else, so that's the good part." Flavin said. "You just have to think you are going to be one of the survivors, and the longer you stay alive, the more hope there is for a new drug that will help you." In early April, Glaxo stopped enrollment in the Tykerb trial early because the drug combined with chemotherapy clearly was improving the outcome for patients without a substantial increase in side effects compared to chemotherapy alone. The London-based company later this year plans to file for approval with the U.S. Food and Drug Administration and European regulators to market Tykerb based on these results, said spokeswoman Michele Meeker. Even after a drug has been successful in a Phase III trial like the Tykerb study, it still might take six to 12 months before that drug is approved for sale. Glaxo will ask U.S. regulators for a quicker review of Tykerb, said Dr. Paolo Paoletti, director of the company's oncology medicine development center. The Breast International Group, an organization of European doctors, will launch a study of Tykerb in 8,000 women with early-stage breast cancer before year's end. Tykerb also has shown preliminary efficacy in renal and head and neck cancers and a rare type of illness called inflammatory breast cancer. The drug also might stop the spread of breast cancer to the brain. It is unclear whether the well-established Herceptin and Tykerb will compete, or if they will be a good combination that could prevent the need for chemotherapy in some women, Vogel said. Regardless, the apparent potency of Tykerb points to a sea change in the way doctors approach cancer treatment. Until recently, the best known way to save cancer patients was to blast them with toxic chemicals that destroyed cancer and healthy cells alike. Now there is a growing body of evidence that suggests selecting a particular treatment specially designed for the genetic type of a tumor is safer and more effective. "This is the kind of hopeful stuff we love to see," Vogel said. "It says that our theories about targeting growth factors are proving to be true in the clinic."

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