Astellas Pharma Inc. has obtained marketing approval of their oral androgen receptor signaling inhibitor, XTANDI capsules 40mg (development code: MDV3100; generic name: enzalutamide) for the treatment of patients with castration-resistant prostate cancer in Japan. Astellas filed the application for approval in Japan in May 2013.

XTANDI is a once-daily, oral androgen receptor signaling inhibitor that acts on different steps in the androgen receptor signaling pathway. Enzalutamide has been shown to competitively inhibit androgen binding to androgen receptors, and inhibit androgen receptor nuclear translocation and interaction with DNA.

XTANDI (product name in Europe and the US: XTANDI@), which is being jointly developed and commercialized with US-based company, Medivation Inc. (NASDAQ MDVN), was approved in August 2012 in the U.S. and in June 2013 in Europe for the treatment of metastatic castration-resistant prostate cancer (mCRPC) in patients who have previously received docetaxel (chemotherapy).

Upon receiving this marketing authorization in Japan, Astellas will provide Medivation with a $15 million milestone payment.