MIAMI—Radium-223 chloride radioisotope therapy, a new approach to the treatment of bone metastases, boosted survival, delayed complications and was well-tolerated, according to an interim analysis of the ALSYMPCA trial presented at the annual meeting of the Society of Nuclear Medicine and Molecular Imaging (SNMMI). “This represents a real breakthrough in the management of late-stage prostate cancer,” said Valerie Lewington, BM, MSc, professor of clinical therapeutic nuclear medicine at King’s College in London.

Radium-223 chloride (Ra-223) seeks out bone metastases with alpha particles that are deadly to tumors. Ra-223 has a short range of penetration of alpha particles, sparing nearby healthy tissues and bone marrow.

“Radium-223 offers a completely new approach to the treatment of bone metastases. It systemically treats multiple sites of disease simultaneously and is usually very well tolerated. Serious side effects are unusual, and the risk of bone marrow suppression is low even in patients who have been heavily pretreated with chemotherapy,” said Lewington. ALSYMPCA ((ALpharadin in SYMptomatic Prostate Cancer) focuses on castration-resistant prostate cancer, which is typically characterized by extensive skeletal metastases that are resistant to treatment.

The double-blind study randomized 921 patients in more than 100 centers in 19 countries with two or more bone metastases to Ra-223 or normal saline. Patients received six injections at four-week intervals. Ra-223 patients survived an average of 3.6 months longer than patients who received the placebo. In addition to prolonged survival, those treated with Ra-223 also experienced delayed onset of complications due to bone metastases. The average delay was 5.5 months, according to researchers.

The researchers monitored patients via bone scans and PET imaging.

An expanded access program is underway in the U.S. and a similar program is expected to open in Europe in 2012. Further clinical trials are also being considered. Formal regulatory approval will be sought in mid-2012 in both the U.S. and Europe.

In September 2009, Bayer HealthCare signed an agreement with Algeta for the development and commercialization of Ra-223 dichloride for $800 million. Under the terms of the agreement, Bayer will develop, apply for global health authority approvals, and commercialize Ra-223 dichloride globally. In April, Algeta exercised its option to co-promote Ra-223 dichloride for the treatment of castration-resistant prostate cancer patients with bone metastases in the U.S., in accordance with the agreement with Bayer.

Ra-223 dichloride is an investigational agent and is not approved by the FDA, the European Medicines Agency or other health authorities. Bayer plans to file radium-223 dichloride with regulatory authorities based on the ALSYMPCA data in the second half of 2012.