Johnson & Johnson has entered a definitive agreement to acquire Aragon Pharmaceuticals, a privately-held company focused on developing drugs to treat hormonally-driven cancers, for $650 million upfront and as much as $350 million based on reaching predetermined milestones. The transaction is expected to close in the third quarter of 2013.

The acquisition includes Aragon’s androgen receptor antagonist program. Its lead product candidate is a second-generation androgen receptor signaling inhibitor, ARN-509, in Phase II development for castration resistant prostate cancer (CRPC). Aragon will transfer its other assets to a newly formed company. J&J will not have an ownership stake in the new company or have rights to these products or programs.

“The acquisition of Aragon further enhances our leadership in prostate cancer drug development. ARN-509 complements Zytiga and provides the potential for exciting, novel approaches to treat prostate cancer patients,” said Peter F. Lebowitz, M.D., Ph.D., global therapeutic area head, Oncology for Janssen R&D. “Prostate cancer is one of our main areas of focus, and we are pleased to be adding ARN-509 to our portfolio.”