Pfizer's Xtandi delays prostate cancer spread in early stage disease

Feb 5 (Reuters) - Use of Xtandi in early stage prostate cancer on top of standard hormone therapy reduced the risk of disease spreading or death by 71 percent compared with hormone therapy alone, study results that could lead to significantly increased sales of the Pfizer Inc and Astellas Pharma Inc medicine.

The data from a highly anticipated study released on Monday showed that it took 36.6 months for the disease to spread to other parts of the body in patients who received Xtandi plus androgen deprivation therapy (ADT), a measure known as median metastasis-free survival. That compared with 14.7 months for ADT alone, a highly statistically significant difference of nearly two years.

Subjects in the 1,400-patient study were deemed at elevated risk of developing metastases in the bones or elsewhere.

"The findings from the trial are quite impressive in terms of delaying the visibility of the cancer," said Dr. Maha Hussain, the study's lead investigator who will present the data at a cancer meeting in San Francisco later this week.

She noted that current treatments for this patient population are not life prolonging or significantly impactful, so there is a high unmet need for delaying development of metastases and progression to advanced cancer.

"The data is very likely practice changing," added Hussain, from the Robert H Lurie Comprehensive Cancer Center of Northwestern University.

That would be good news for Pfizer and Astellas, providing a lucrative new outlet for Xtandi. The data has been submitted for review to U.S. and European regulators, the companies said.

Xtandi and rival drug Zytiga from Johnson & Johnson are currently approved for advanced cancer that has spread beyond the prostate.

"The treatment opportunities are almost double than the current indication," Pfizer Chief Operating Officer Albert Bourla told Reuters in a recent telephone interview. "And the financial interest is larger because the duration of treatment is longer."

Prostate cancer is the second most common cancer in men worldwide. More than 164,000 men in the United States are estimated to be newly diagnosed with it this year.

Adverse side effects were similar to those reported in previous Xtandi trials of more advanced cancer patients, the companies said. About 9 percent of patients in the Xtandi arm discontinued treatment due to side effects compared with 6 percent of those on ADT alone.

Major adverse cardiovascular events, such as heart attack, were reported in 5 percent of Xtandi plus ADT patients versus 3 percent with ADT.

Xtandi also significantly delayed median time to prostate-specific antigen (PSA) progression, a biomarker tied to disease worsening - 33.3 months versus 3.9 months.

Overall survival data was not yet available. (Reporting by Bill Berkrot; Editing by Lisa Shumaker)