LONDON (Reuters) - Johnson & Johnson's prostate cancer drug Zytiga has been approved in the European Union, paving the way for the launch of a new treatment for men whose disease has progressed after chemotherapy, the company said on Wednesday.

The decision was expected after European regulators endorsed the treatment in July. J&J's Janssen unit has European rights for the product. Zytiga, or abiraterone, works by blocking the synthesis of testosterone, which can fuel cancer growth.

Abiraterone was developed by researchers at the Institute of Cancer Research and London's Royal Marsden Hospital, and British pharmaceutical firm BTG will receive an undisclosed milestone payment following the approval together with a royalty on worldwide sales.

The medicine was approved in the United States in May.