Dec 14 (Reuters) - A late-stage trial found that continuing treatment with Pfizer Inc's cancer drug Xtandi in addition to a regimen of Zytiga and a steroid worked no better than the two other drugs alone in patients with advanced prostate cancer whose disease had worsened, the company said on Wednesday.

Zytiga, or abiraterone acetate, is sold by Johnson & Johnson .

Xtandi, currently approved in the United States for patients with advanced prostate cancer that has spread, is sold by Pfizer in partnership Astellas Pharma Inc.

Pfizer acquired its stake in the cancer drug, also known as enzalutamide, earlier this year with its $14 billion buyout of Medivation Inc.

Pfizer and Astellas, in a release, said they remain committed to continuing to explore the clinical potential of Xtandi.

(Reporting By Deena Beasley; Editing by Tom Brown)