To assess the effect of ASP3550 on the maintenance of serum testosterone suppression in patients with prostate cancer

Two doses of ASP3550 were administered to patients with prostate cancer. The primary efficacy variable was the effect of ASP3550 on the maintenance of serum testosterone suppression. In addition, the safety and pharmacokinetics of ASP3550 will be investigated.

Inclusion Criteria:

• Is a male patient with histologically proven prostate cancer (adenocarcinoma) of all stages
• Is a patient in whom endocrine treatment is indicated. Patients with rising serum PSA after having prostatectomy or radiotherapy performed with curative intention may be included
• Has a serum testosterone level above 1.5 ng/mL at screening
• Has an ECOG (Eastern Co-operative Oncology Group) P.S. (Performance Status) score of 0 to 2

Exclusion Criteria:

• Previous or present endocrine treatment for prostate cancer. However, patients who have undergone neoadjuvant/adjuvant endocrine therapy for a maximal duration of 6 months and in whom prostatectomy or radiotherapy was terminated at least 6 months preceding Screening Visit may be included
• Is being treated with a 5α-reductase inhibitor
• Is a candidate for curative therapy, i.e., radical prostatectomy or radiotherapy within 12 months
• Has concurrent or a history of severe asthma (defined as a need for daily treatment with inhalation steroids), anaphylactic reactions, severe urticaria and angioedema