US regulators have approved Bayer's Xofigo as a treatment for prostate cancer, just three months after it was assigned a priority review.

The US Food and Drug Administration has issued a green light for the injection for use in men with symptomatic late-stage castration-resistant prostate cancer that has spread to bones but nowhere else, three months ahead of schedule.

Xofigo, which is based on radium 223 and was developed by Norwegian group Algeta, is only intended for men whose cancer has spread following medical or surgical intervention to lower levels of testosterone.

The drug works by binding with minerals in the bone to deliver radiation directly to bone tumours, which thereby can limit damage to the healthy surrounding tissues and seems to have a beneficial impact on overall survival.

Its approval comes on the back of Phase III trial data showing that men taking Xofigo lived a median of 14 months compared to 11.2 months for those receiving a placebo.

According to Richard Pazdur, director of the Office of Hematology and Oncology Products in the FDA’s Center for Drug Evaluation and Research, following approval of Medivation/Astellas' Xtandi in August 2012, Xofigo is now the second prostate cancer drug approved in the US in the past year "that demonstrates an ability to extend the survival of men with metastatic prostate cancer”.

Bayer owns global exclusive marketing rights for the drug, which will be co-promoted with Algeta in the US.

Commercial production of Xofigo is currently underway, and first doses should be ready for patients within a few weeks, the firms said. 

Analysts largely expect that the treatment, which is also under review in Europe, could hit peak sales just shy of one billion dollars, according to media reports.