TAK-683 (s.c.; 10, 30, or 100 pmol/h; once daily; 4 weeks) provides a promising for suppressing reproductive functions and hormone-related diseases such as prostate cancer. TAK-683 (s.c.; 0.008, 0.08, 0.8, or 8 μmol/ml/kg; once daily; 7 days) induces an increase in plasma luteinizing hormone and testosterone levels; however, after day 7, plasma hormone levels and genital organ weights are reduced. TAK-683 (s.c.; 2.1-21 nmol/kg/day; once daily; 12 weeks) has a longer-term evaluation in prostate cancer model, serum concentrations of PSA are reduced in rats, PSA concentrations are reduced to below the limit of detection (0.5 ng/ml)) in all rats by day 14 [1].