Radium Ra 223 Dichloride, an alpha radiation-emitting drug also known as radium-223, will be considered as a treatment for patients who have castration-resistant prostate cancer (CRPC) with bone metastases under the FDA’s priority review program.

The FDA grants priority review to drugs that may represent a significant improvement over existing treatments for a condition, or when there is no adequate therapy. The agency’s goal is to complete priority reviews within six months of the 60-day filing receipt of a new drug application, or a total of eight months.

“We are pleased the FDA has granted priority review of the radium-223 new drug application for the treatment of patients with castration-resistant prostate cancer that has metastasized to the bones. Receiving this designation marks another positive milestone for radium-223 and underscores Bayer’s ongoing commitment in oncology,” said Pamela A. Cyrus, MD, vice president and head of US Medical Affairs for the drug’s developer, Bayer HealthCare Pharmaceuticals.

Bayer’s request for review follows the phase III ALSYMPCA trial, in which 922 men were randomized 2:1 to receive either radium-223 plus current standard of care, or placebo plus current standard of care.

Median overall survival was 14 months in the experimental arm versus 11.2 months in the control arm (P = .00185). Median time to the first skeletal-related event was 13.6 months versus 8.4 months, respectively (P = .00046), representing a 64% improvement with radium-223.

The treatment is administered in five minutes on an outpatient basis.

“Injectable radium-223 goes to new areas of bone formation, such as cancer metastasis, and emits alpha particles, which are highly damaging and short range. The tumor cells are killed, but the more distant cells in the bone marrow are spared,” explained Chris Parker, MD, of the Royal Marsden Institute in Surrey, United Kingdom, during the European Multidisciplinary Cancer Congress in 2011. “Only a few hits are required with radium-223, whereas with beta radiation [used in radiopharmaceuticals], thousands of hits are needed and there is damage to the surrounding tissue.”