On May 15th, 2013 the FDA approved the alpha particle-emitting Radium Ra 223 dichloride (Xofigo) as a radiotherapeutic agent for the treatment of patients with castration-resistant prostate cancer, symptomatic bone metastases and no known visceral metastatic disease. The therapeutic component is the alpha particle-emiting Radium 223 isotope. It mimics calcium and binds to bone minerals is areas of rapid cell division, where it preferentially affects cancer cells. The radiation causes high levels of DNA double-strand breaks in adjacent cells, causing the killing of rapidly dividing cells, such as bone metastases.
After intravenous injection, Ra 223 is rapidly cleared from the blood and distributed primarily into bone or is excreted into intestine. The levels of radioactivity detected in the blood rapidly decrease and, at 24 hours, reach less than 1% of the administered dose. The alpha particle emission range of Ra 223 is 100 micrometers which protects against damage to normal surrounding tissue.
The molecular weight of Ra 223 dichloride, 223RaCl2, is 293.9 g/mol. Ra 223 has a half-life of 11.4 days and an activity of 1.9 MBq (51.4 microcurie)/ng.
In Phase 3 clinical trials, Xofigo increased survival to 14.9 months as compared to 11.3 for placebo.
Xofigo is a product of Bayer The Prescribing Information can be found here.