Johnson & Johnson has completed its $1-billion purchase of private US cancer drug development firm Aragon Pharmaceuticals.

The move has bought the healthcare giant access to Aragon's androgen receptor antagonist programme, the most advanced compound in which is ARN-509, a second generation androgen receptor signalling inhibitor in Phase II for castration-resistant prostate cancer. 

According to Peter Lebowitz,Global Therapeutic Area Head of Oncology at J&J, the acquisition "strengthens our prostate cancer pipeline with a second-generation, potentially best-in-class compound".

"It builds on our existing leadership position with Zytiga (abiraterone acetate), and, if approved, we are hopeful ARN-509 will allow us to meet the needs of an even broader range of prostate cancer patients," he said.

J&J announced earlier this year that it is shelling out $650 million in cash upfront and $350 million in development milestones for Aragon's androgen receptor antagonist programme.

However, other programmes, such as ARN-810, in development for metastatic breast cancer, are not included in the deal and will be spun out into a separate group called Seragon Pharmaceuticals, which will be financed by current Aragon investors and lead by current chief executive Richard Heyman.