An experimental drug called Tykerb might delay the progression of advanced breast cancer in some patients, new research shows.

The findings were presented in Atlanta at the American Society of Clinical Oncology’s annual meeting. The researchers included Charles Geyer, MD, director of Breast Medical Oncology at Pittsburgh’s Allegheny General Hospital.

Tykerb, which has not yet been submitted for FDA approval, is taken as a pill. It targets a protein called HER2/neu, which is involved in the growth of some cancer cells. Tykerb blocks part of the HER2/neu’s receptor.

About 20 percent to 25 percent of breast cancer patients have HER2/neu breast cancer, which may be more aggressive and possibly more resistant to chemotherapy and hormone therapy than other forms, notes the Susan G. Komen Breast Cancer Foundation.

Herceptin Study Fared Better Than Expected

Tykerb Study

Geyer’s study included 321 patients with advanced breast cancer that was positive for HER2/neu.

Participants had already gotten chemotherapy and had taken the drug Herceptin, which also targets HER2/neu breast cancer.

Geyer and colleagues split the patients into two groups. Both got the chemotherapy drug Xeloda. One group also took Tykerb.

Interim results showed that 114 cancers had progressed. On average, breast cancer progressed after 36.9 weeks (about 9.2 months) with Tykerb and Xeloda, compared with 19.7 weeks (about 4.9 months) with Xeloda alone.

At that point, the researchers recommended stopping enrollment in the study and reporting the interim results. In their abstract, they write that Tykerb provided “a clinically meaningful” impact on HER2/neu breast cancer in patients pretreated with chemotherapy and Herceptin.

Fewer American Women Dying of Breast Cancer

Side Effects

Diarrhea and hand/foot rashes were more common in patients taking both Tykerb and Xeloda than in those only taking Xeloda.

The two groups had similar percentages of patients who quit the study: 11 percent for Xeloda alone; 14 percent for Tykerb plus Xeloda.

About 2 percent of patients taking Tykerb with Xeloda had a 20 percent drop in the pumping strength of the heart’s left ventricle, compared to 1 percent of those only taking Xeloda.

That problem appeared to be temporary. In all patients, the heart’s left ventricle regained its previous pumping strength, the study shows.

The study was funded by the drug company GlaxoSmithKline, Tykerb’s maker. GlaxoSmithKline is a WebMD sponsor.

GlaxoSmithKline plans to submit Tykerb for regulatory approval in the U.S. and Europe in the second half of 2006, states a company news release.

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By Miranda Hitti, reviewed by Louise Chang, MD

SOURCES: American Society of Clinical Oncology, Atlanta, June 2-6, 2006. National Cancer Institute: “Dictionary of Cancer Terms.” Susan G. Komen Breast Cancer Foundation: “Diagnosis: Tumor Characteristics.” News release, GlaxoSmithKline. Associated Press.