Johnson & Johnson is lining up prostate-cancer drug contenders. The multidisciplinary behemoth announced Monday that it was buying up Aragon Pharmaceutical’s experimental androgen receptor antagonist ARN-502 for $650 million up-front and up to $350 million in additional milestones. Aragon is shuttling its other assets into an independent company.

The move means the Phase II drug is not just poised to do battle with Bayer’s just-approved Xofigo, Astellas/Medivation’s relatively new Xtandi and Dendreon’s lagging Provenge. It means Johnson & Johnson may have a potential patent loss stop-gap: Zytiga, the pill for castration-resistant prostate cancer that’s sold by J&J’s Janssen subsidiary, loses its exclusivity in 2016.

The potential treatment pool is a large one: the latest Centers for Disease Control data indicates that 206,640 men were diagnosed with prostate cancer in 2009 and 28,088 died of it that very same year. It is the most common form of cancer among men, and treatments can vary from watchful-waiting scenarios in which doctors and patients hold off before taking action, and can also include interventions such as external radiation, internal radiation, hormone therapy that halts testosterone production, and surgery.

Prostate-cancer screening using the Prostate Specific Antigen has been a source of much debate, with critics saying the results are too broad and encourage too many men to pursue surgery, which is often linked to erectile dysfunction. Five years ago the US Preventive Services Task Force recommended that men 75 and older no longer be screened, a move that prompted a 7.9% drop in screenings among the 75-plus age group by 2010.