The purpose of this study is to evaluate hormone dynamics, pharmacokinetics, safety, and efficacy of TAP-144-SR(6M) against TAP-144-SR(3M) in prostate cancer patients previously treated with hormonal therapy.

Inclusion Criteria:

1. The participant has histopathologically confirmed prostate cancer in Japanese.
2. The participant has prostate cancer in the clinical stages of T1b-T4, N-any and M-any by TNM classification on clinical diagnosis at the time of diagnosis.
3. The participant has ECOG performance status of grades 0, 1, or 2 at screening.
4. The participant with PSA level which has not increased 25 % or greater and 2 ng/mL or more from the nadir at the measurement points 4 weeks or longer apart within the screening period of 12 weeks.
5. Patients who receive the marketed product for 3 months (LEUPLIN SR FOR INJECTION KIT 11.25) at screening
6. Patients who have received the marketed products, TAP-144-SR (1M) and TAP-144-SR (3M), for 24-96 weeks in total at the scheduled starting date of the study drug, but not including administration period treated as neoadjuvant therapy for prostatectomy and/or radiation therapy
7. Patients who have continued the nonsteroidal antiandrogen for longer than 12 weeks at the scheduled starting date of the study drug, if a nonsteroidal antiandrogen is concomitantly administered
8. The participant with a serum testosterone level at screening < 100ng/dL
9. The participant meets the following criteria of renal, bone-marrow and hepatic functions on the laboratory test results at screening:

（1） Renal function: serum creatinine level< 1.5 times the upper limit of normal (ULN) （2） Bone-marrow function: white blood count ≥ 3,500/ mm3, platelet count ≥ 100,000/L, hemoglobin ≥ 10.0g/dL （3） Hepatic function: AST(GOT), ALT(GPT), ALP and total bilirubin ≤ 2.5 times the ULN 10. The participant's life expectancy is at least 24 months at informed consent.

Exclusion Criteria:

1. The participant has active multiple primary cancers, (synchronous multiple primary cancer or metachronous multiple primary cancer with the disease-free survival ≤ 5 years)
2. The participant has received surgical castration.
3. The participant has ever received LHRH agonists other than commercially available 1-month or 3-month depot of leuprolide acetate.
4. The participant has ever received LHRH antagonists.
5. Patients who have previously received estrogen preparations or corticosteroids for prostate cancer
6. Patients who have previously received chemotherapy for prostate cancer
7. Patients who are receiving or received the marketed product for 3 months (LEUPLIN SR FOR INJECTION KIT 11.25) or the marketed products for 1 month (LEUPLIN FOR INJECTION 3.75 and KIT 3.75) as an adjuvant therapy after prostatectomy and/or radiotherapy
8. Patients who are receiving or received the marketed product for 3 months (LEUPLIN SR FOR INJECTION KIT 11.25) for intermittent androgen deprivation therapy
9. Patients who received the following drugs within 24 weeks (168 days) after starting the study drug: Steroidal antiandrogens, type II 5α-reductase inhibitors
10. The participant received any of the following within 16 weeks (112 days) prior to study enrollment:

（1） Radiotherapy. As for I-125 brachytherapy, within 35 weeks (245 days) prior to study enrollment.

（2） Prostatectomy （3） Experimental therapy including high-intensity focused ultrasound therapy (HIFU), immunotherapy, and gene therapy 11. Patients who received the following drugs within 4 weeks (28 days) before starting the study drug: Testosterones, ketoconazole（except for external preparations）, spironolactone, corticosteroids (excluding their inhalants and external preparations), and Chinese medicines and dietary supplements containing saw palmetto 12. Patients whose QTcF interval exceeded 460 msec on the 12-lead electrocardiogram at screening 13. The participant has a history of hypersensitivity to synthetic LHRH, LHRH derivative or any component of the study drug.

14. The participant has central nervous system metastasis which requires treatment or which is symptomatic.

15. The participant already has a history or has a complication or may have renal disorder caused by spinal cord compression or ureteric obstruction.

16. The participant has a history of serious drug allergic reaction/hypersensitivity 17. The participant has a history of, or has been diagnosed with thromboembolism including myocardial infarction, cerebral infarction, venous thrombosis, and pulmonary embolism, or cardiac failure