Algeta ASA and partner Bayer AG disclosed FDA approval Wednesday for Xofigo (radium Ra 223 dichloride) in castration-resistant prostate cancer, with the agency's nod coming three months ahead of the Aug. 14 PDUFA date.

Xofigo, an alpha particle-emitting radioactive therapeutic agent, was approved based on data showing that the drug produced an overall survival benefit with antitumor effects on bone metastases.

"We're actually delighted," Algeta CEO Andrew Kay told BioWorld Today. "This is a product that meets high medical need and a reflection of the quality of the data we produced in the Phase III study."

In Algeta's Phase III ALSYMPCA trial, Xofigo, formerly known as Alpharadin, improved overall survival by 44 percent, resulting in a 30.5 percent reduction in the risk of death compared to placebo. Median overall survival was 14.9 months in the Xofigo group compared to 11.3 months for placebo.

Adverse events included anemia (31 percent vs. 31 percent), neutropenia (5 percent vs. 1 percent) and thrombocytopenia (12 percent vs. 6 percent) for Xofigo compared to placebo. Non-hematologic adverse events included bone pain, nausea, diarrhea and vomiting.

Additional analysis revealed that patients treated with Xofigo had significantly better quality of life, with improved functioning and well being compared to those treated with placebo.

Kay said there was also a delay in time to the first symptomatic skeletal events.

The Oslo, Norway-based company's next step will be to work closely with its partner Bayer to launch the product.

A deal between the companies signed in 2009 gave Algeta a 50-50 co-promotion option, which it exercised in 2012. (See BioWorld Today, April 18, 2012.)

Under that 2009 licensing agreement, Algeta had the right either to receive a royalty on sales or take ascending co-promotion rights – from 25 percent up to a maximum of half the market.

Algeta went for the full 50 percent because it decided that Xofigo was a potential blockbuster.

Kay said that because the FDA had a track record of early approvals for oncology products, the company is fully prepared to launch the product "in a couple of weeks."

Xofigo is an alpha particle-emitting radioactive agent that binds minerals in the bone to deliver radiation directly to bone tumors. It is designed to limit damage to surrounding normal tissues.

"We are the world leaders in alpha emitting pharmaceuticals," Kay said. "Xofigo is the first in this new class of products."

Kay pointed out that the drug's label is not restricted for pre- or post-chemo patients. "The indication is for all patients with bone metastases who do not have visceral metastases," Kay said.

According to Kay, the only therapy option for advanced prostate cancer patients previously has been chemotherapy. However, the patients are generally older, clinically fragile, and often are unable to tolerate chemotherapy. Kay said that Xofigo is less toxic and has fewer side effects than conventional chemotherapy.

Jefferies and Co. analyst Tom Tarrant projected $2.1 billion peak sales for the drug. He noted that Bayer has not yet made a move on label expansion studies. "We still await clarity . . . on the strategy for expanding Radium-223 development, importantly further studies in metastatic castrate-resistant prostate cancer (mCRPC), potentially in combination with oral Zytiga/Xtandi and/or in earlier stage patients, but also a possible Phase II trial in metastatic breast cancer."

He said Bayer indicated it is committed to beginning further studies in mCRPC by the end of 2013.

Tarrant based peak sales predictions on Algeta's "impressive Phase III data," well-understood mechanism of action, partnership with Bayer and high unmet medical need.