Astellas' prostate-cancer prodigy Xtandi shines as pre-chemo treatment

Soon after Xtandi hit the market last year, analysts were figuring that the prostate cancer drug would help pump up that market to $9.1 billion by 2021. Already, the drug from Medivation ($MDVN) and Astellas is racking up big sales; it made FiercePharma's recent list of superstar drug launches, thanks to the $157.8 million it brought in for the first half of this year.

And now, the drug has reached a key milestone: success in a Phase III trial eyeing Xtandi as a prechemo treatment for advanced prostate cancer. Independent monitors called for a halt, to allow patients in the control arm to receive Xtandi, too. According to the companies, Xtandi cut the risk of death by 30%, bringing overall survival to an estimated median of 32.4 months, compared with 30.2 months for patients in the placebo arm. The actual stats will be unveiled at a conference at some point.

The difference doesn't seem to be much--just 2.2 months' worth, according to the investigators' estimates--but the patients treated had advanced prostate cancer that had progressed despite hormonal treatment. As The Street points out, Johnson & Johnson's ($JNJ) rival drug Zytiga delivered a 21% reduction in the risk of death in a similar study.

"To my knowledge, the benefits in overall survival ... are unprecedented in this patient population," said Dr. Tomasz M. Beer, deputy director of the Knight Cancer Institute at Oregon Health & Science University, and one of the study's lead authors.

Astellas CMO Sef Kurstjens said he is "very pleased about these results" and plans to work with Medivation to win a broader indication for Xtandi. The companies say they plan to start working with regulatory agencies on the new indication beginning early next year. Zytiga already has the FDA's nod for first-line treatment in patients with advanced prostate cancer, so Xtandi will need to win broader use quickly if it wants to keep up.

- see the release from Medivation and Astellas
- read the coverage from The Street

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