(Adds analyst sales forecast, collaboration details)
Sept 10 (Reuters) - U.S. health regulators approved the use of Medivation Inc’s and Astellas Pharma Inc’s advanced prostate cancer drug Xtandi in men who have not yet received chemotherapy, the companies said on Wednesday, significantly expanding the potential patient population for the oral medicine.
The expanded Food and Drug Administration approval will also enable the drug to better compete with Johnson & Johnson’s Zytiga. The approval triggers $90 million in milestone payments to Medivation by Japan’s Astellas under a collaboration agreement.
Xtandi, known chemically as enzalutamide, originally gained U.S. approval in 2012 for use in patients with castration-resistant prostate cancer that has spread beyond the prostate only after they had first received chemotherapy treatment.
“The average duration of treatment should double and the addressable patient population triple in the pre-chemo setting,” Sanford Bernstein analyst Geoffrey Porges said in a research note earlier this week.
SMBC NIKKO Securities has forecast eventual peak annual Xtandi sales reaching $5 billion.
Astellas reported worldwide Xtandi sales of $227 million in the second quarter.
Under their collaboration agreement, Medivation and Astellas split U.S. sales of the drug, while the Japanese company is responsible for all regulatory, manufacturing and sales of Xtandi outside the United States.
The additional approval was based on results of a Phase III trial in which Xtandi demonstrated an overall survival benefit, reducing the risk of death by 29 percent compared with a placebo. It also significantly reduced the risk of disease progression, delayed the need for chemotherapy and delayed skeletal problems in cancer that had spread to the bones.
Medivation shares rose to $97.95 in after-hours trading from a Nasdaq close at $96.89. (Reporting by Bill Berkrot; Editing by James Dalgleish and Lisa Shumaker)