Astellas Pharma and partner Medivation have filed their investigational prostate cancer drug enzalutamide with the US Food and Drug Administration.

A New Drug Application for enzalutamide, formerly known as MDV3100, has been submitted for patients with castration-resistant prostate cancer who have received docetaxel therapy. Medivation has requested a priority review from the FDA which would mean that the agency would make a decision win six months.

Enzalutamide is an oral, once-daily agent that is an androgen receptor signaling inhibitor. In the Phase III AFFIRM trial, the treatment was well tolerated, while serious adverse events were lower in the enzalutamide group than for those on placebo.

The companies linked up in October 2009 and the deal could be worth up to $765 million to Medivation. The filing is a major boost for the latter firm, which suffered earlier this year when partner Pfizer pulled out of a pact for the Alzheimer's disease drug Dimebon (latrepirdine).

As for Astellas, US advisers recommended approval of its new bladder drug mirabegron in April and a decision is due by June 29.