The FDA has approved radium-223 injection (Xofigo, Bayer) for treating castration-resistant prostate cancer with symptomatic bone metastases.

It is the first alpha particle-emitting radioactive therapeutic agent approved by the FDA. In a pivotal phase 3 trial (ALSYMPCA), radium-223, the median overall survival time was 14.9 months for patients who received the drug compared with 11.3 months among placebo recipients, a significant difference that translated into a 31% decreased risk death  associated wth radium-223 therapy.

The most common adverse effects in patients receiving radium-223 in the ALSYMPCA trial were nausea, diarrhea, vomiting, and peripheral edema.

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Radium-223 mimics calcium and forms complexes with the bone mineral hydroxyapatite at areas of increased bone turnover, such as bone metastases. Here, the alpha particles exert their anti-tumor effect on cancer cells. Alpha particles have an extremely short range, which helps to limit damage to surrounding normal tissue.

The first doses of the drug are expected to be ready within a few weeks, according to a press release issued by Algeta ASA, of Oslo, Norway, which is co-promoting radium-223 in the U.S. with Bayer.