Drug maker Pfizer Inc. (PFE), Thursday said that it has discontinued a late-stage trial of Sutent, indicated in the treatment of advanced breast cancer. The company, however, said it is evaluating Sutent in several other phase 3 and phase 2 trials.

The New York-based pharmaceutical giant stopped its SUN 1107 phase 3 study, which evaluated single-agent sunitinib versus single-agent capecitabine for the treatment of a broad range of patients with advanced breast cancer after failure of standard treatment.

An independent Data Monitoring Committee found that even if the trial had been allowed to continue, treatment with single-agent sunitinib would be unable to demonstrate a statistically significant improvement in the primary endpoint of progression-free survival compared to single-agent capecitabine in the study population. Data from this trial are currently being analyzed.

Sutent is an oral multi-kinase inhibitor, which is currently approved for the treatment of both gastrointestinal stromal tumor after disease progression on or intolerance to imatinib mesylate, and advanced/metastatic renal cell carcinoma. The drug works by blocking multiple molecular targets implicated in the growth, proliferation and spread of cancer.

Last month, Pfizer said that its late-stage study of Sutent in patients with advanced pancreatic islet cell tumors was stopped early after the drug significantly increased progression free survival in patients.

In international markets, sales growth of Sutent continues to outpace its growth in the U.S. In the fourth-quarter of 2008, Sutent sales in the U.S. were $66 million, an increase of 5% year over year, while international sales of the drug were $154 million, an increase of 30% over the year-ago period. Overall Sutent sales in the fourth-quarter of 2008 were $220 million, a 21% increase over the comparable quarter a year before.

Safety concerns over Sutent had cropped up after reports linking the drug to heart failure, heart attacks and hypertension, appeared in a medical journal The Lancet in December 2007.

Analysis of the study, published in The Lancet, showed that 35 of the total 75 patients with gastrointestinal stromal tumors treated with Sutent, developed hypertension, 2 had heart attacks and 5 had heart failure.

According to the results of small study of patients with renal cell carcinoma (a type of kidney cancer) and gastrointestinal stromal tumor, Sutent causes heart failure more often than previously recognized.

But according to Pfizer, the risk-benefit profile of Sutent has been well established and in larger studies Sutent showed lower incidences of heart effects, including heart failure, high blood pressure and reduced pumping function. In addition the cardiovascular events are acknowledged on current FDA approved labeling for Sutent, which suggests monitoring in patients with cardiac risk factors.

Though the SUN 1107 phase 3 study was stopped, Pfizer said it continues to evaluate Sutent as a single-agent and in combination with standard-of-care chemotherapy in specific patient populations with advanced breast cancer through three additional phase 3 and two phase 2 trials.

Pfizer is currently trading at $13.93, down 6 cents, on a volume of 28.60 million shares.

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