ABIRATERONE DECANOATE for Prostate cancer | Advanced prostate cancer

Inclusion criteria

• {"criterion_text":"- 1. Participant is male and at least 18 years of age or older at time of consent.\n- 16. Participant has been diagnosed with mHSPC documented by metastatic lesions on a bone scan, CT, MRI or PSMA-PET. (Cohort 2)\n- 21. Participant has been diagnosed with mCRPC or mHSPC documented by metastatic lesions on a bone scan, CT, MRI, or PSMA-PET. (Cohort 3)\n- 2. Participant is diagnosed with histologically or cytologically confirmed adenocarcinoma of the prostate without neuroendocrine differentiation or small cell features.\n- 3. Participant has Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1, or ECOG performance status of 2 if due to bone pain.\n- 4. Participant with mHSPC must have an estimated life expectancy of ≥ 12 months or >6 months if participant has metastatic castration-resistant prostate cancer (mCRPC).\n- 5. Participant is able to understand and comply with all study requirements and procedures, including completion of patient-reported outcome questionnaires, based on the assessment of the investigator.\n- 6. Male participant: ●Must agree to use defined forms of contraception with female partner(s) of childbearing potential (including breastfeeding partner) throughout the treatment period and for 7 months after final ASP5541 or for 3 months after AA study intervention administration. ●Must agree to remain abstinent or use a condom with pregnant partner(s) for the duration of the pregnancy throughout the investigational period and for 7 months after final ASP5541 or for 3 months after AA study intervention administration. ●Must not donate sperm during the treatment period and for 7 months after final ASP5541 or for 3 months after AA study intervention administration.\n- 7. Participant has provided informed consent, which includes compliance with the requirements and restrictions listed in the ICF and protocol\n- 9. Participant agrees not to participate in another interventional study while receiving ASP5541 in the present study.\n- 11. Participant has been diagnosed with mCRPC documented by metastatic lesions on a bone scan, CT, MRI or prostate-specific membrane antigen positron emission tomography (PSMA-PET). (Cohort 1)"}

Exclusion criteria

• {"criterion_text":"- 1. Participant has any concurrent disease, infection or comorbid condition that interferes with the ability of the participant to participate in the study, which places the participant at undue risk or complicates the interpretation of data in the opinion of the investigator.\n- 11. Participant has moderate or severe hepatic impairment (Child-Pugh Class B or C).\n- 12. Participant has a known history of HIV infection. No HIV testing is required unless mandated by a local health authority.\n- 13. Participant has a body mass index > 40 kg/m2.\n- 14. Participant has a history of drug or alcohol abuse according to DSM-5 criteria within 2 years before screening.\n- 31. For Cohort 1: Prior treatment with a second-generation ARPI (e.g., AA, enzalutamide, apalutamide or darolutamide). NOTE: limited treatment with a second-generation ARPI in the neo-adjuvant, adjuvant or non-metastatic biochemically recurrent setting is permitted as long as there was no evidence of disease progression for at least 6 months following last dose.\n- 34, 37, 40. Participant has clinically significant cardiac disease.\n- 35. For Cohort 2: Prior treatment with a second-generation ARPI (e.g., AA, enzalutamide, apalutamide or darolutamide). Note: limited treatment with a second-generation ARPI in the neo-adjuvant, adjuvant or non-metastatic biochemically recurrent setting is permitted as long as there was no evidence of disease progression for at least 6 months following last dos\n- 3. Participant has a known additional malignancy beyond prostate cancer that requires active treatment, with the exception of any of the following: ● Adequately treated basal cell carcinoma, squamous cell carcinoma of the skin or in situ carcinoma of any type ● Adequately treated Stage I cancer from which the participant is currently in remission and has been in remission for ≥ 2 years ● Any other cancer from which the participant has been disease-free for ≥ 5 years The medical monitor should be contacted for any questions regarding this exclusion criterion.\n- 4. Participant has any unresolved National Cancer Institute - Common Terminology Criteria for Adverse Events (NCI-CTCAE) (version 5.0) Grade > 2 toxicity at the Screening visit. NOTE: A participant receiving ongoing hormone replacement therapy for endocrine immune-related AEs without clinical symptoms will not be excluded.\n- 5. Participant has had major surgery (e.g., requiring general anesthesia) within 90 days before screening, or will not have fully recovered from surgery, or has major surgery planned during the time the participant is expected to participate in the study.\n- 6. Participant has/had febrile illness or symptomatic, viral, bacterial (including upper respiratory infection) or fungal (noncutaneous) infection within 28 days prior to Cycle 1 Day 1.\n- 7. Participant received a blood transfusion within 1 month of Cycle 1 Day 1.\n- 8. Participant has a history of impaired pituitary or adrenal gland function (e.g., Addison's disease, Cushing's syndrome).\n- 9. Participant has HbA1c > 10% and was previously diagnosed with diabetes mellitus. Participant has HbA1c > 8% and was not previously diagnosed with diabetes mellitus (excluded participants may be rescreened after referral and evidence of improved control of their condition).\n- 10. Participant has jaundice or known current active liver disease from any cause, including hepatitis A (hepatitis A virus IgM positive, but testing for hepatitis A in screening is not required), hepatitis B [HBsAg positive, or HBV DNA positive if HBsAg negative/anti-HBc positive]), or hepatitis C (HCV antibody positive, confirmed by HCV RNA)."}

Primary endpoints

• {"endpoint_text":"- • Proportion of ARPI-naïve mCRPC participants with PSA decline ≥ 90% from baseline (Cohort 1)","definition_or_measurement_approach":"PSA decline measured from baseline; endpoint reported as proportion of ARPI‑naïve mCRPC participants achieving ≥90% PSA reduction from baseline (Cohort 1)."}
• {"endpoint_text":"- • Rates of no mineralocorticoid toxicity, defined as experiencing neither Grade ≥ 1 hypokalemia nor Grade ≥ 2 hypertension (Cohort 2 safety-run in)","definition_or_measurement_approach":"Defined as experiencing neither Grade ≥1 hypokalemia nor Grade ≥2 hypertension during the Cohort 2 safety run-in."}
• {"endpoint_text":"- • Proportion of mHSPC participants with PSA ≤ 0.2 ng/mL at 8 months (Cohort 2)","definition_or_measurement_approach":"Proportion of mHSPC participants with PSA ≤ 0.2 ng/mL at the 8‑month timepoint."}
• {"endpoint_text":"- • dose-limiting toxicities (DLTs), AEs, serious Adverse Events (SAEs), laboratory results (including chemistry, hematology and urinalysis), electrocardiograms (ECGs), vital signs, physical examinations and ECOG performance status scores (Cohort 3)","definition_or_measurement_approach":"Safety endpoints measured by occurrence of DLTs, AEs, SAEs and changes in laboratory tests (chemistry, hematology, urinalysis), ECGs, vital signs, physical examinations and ECOG scores in Cohort 3."}

Secondary endpoints

• {"endpoint_text":"- • Radiographic progression-free survival (rPFS), defined as the time from date of randomization/first dose date until the date of radiological progressive disease (PD) per RECIST v1.1 and PCWG3 as determined by investigator or death from any cause • Prostate-specific antigen (PSA) decline ≥ 50% from baseline • PSA decline ≥ 90% from baseline (Cohorts 2 and 3 only)","definition_or_measurement_approach":"rPFS: time from randomization/first dose to radiological PD per RECIST v1.1 and PCWG3 by investigator or death. PSA declines measured as percent reduction from baseline; PSA ≥50% and ≥90% as specified (≥90% for Cohorts 2 and 3 only)."}
• {"endpoint_text":"- • PSA undetectable rate (≤ 0.2 ng/mL) (Cohorts 1 and 3 only) • PSA undetectable rate (≤ 0.02 ng/mL) • Time to PSA progression per PCWG3 criteria • Objective response rate per RECIST v1.1 for soft tissue disease and PCWG3 for bone disease • Duration of response per RECIST v1.1 for soft tissue disease and PCWG3 for bone disease","definition_or_measurement_approach":"PSA undetectable rates at specified thresholds; time to PSA progression per PCWG3; objective response and duration of response assessed per RECIST v1.1 for soft tissue and PCWG3 for bone disease."}
• {"endpoint_text":"- • Best overall response per RECIST v1.1 for soft tissue disease and PCWG3 for bone disease","definition_or_measurement_approach":"Best overall response assessed using RECIST v1.1 for soft tissue lesions and PCWG3 criteria for bone disease."}
• {"endpoint_text":"- • AEs, SAEs, laboratory results (including chemistry, hematology, urinalysis • spot urine potassium and creatinine (Cohort 2 only) • ECGs, vital signs, physical examinations and ECOG performance status scores (Cohorts 1 + 2 only)","definition_or_measurement_approach":"Safety monitoring including AEs/SAEs, labs (chemistry, hematology, urinalysis); spot urine potassium/creatinine in Cohort 2; ECGs, vitals, physical exams and ECOG in Cohorts 1 and 2."}
• {"endpoint_text":"- • Testosterone suppression to ≤ 1 ng/dL, or achieves a ≥ 90% reduction from baseline level • Mean testosterone values by time point","definition_or_measurement_approach":"Testosterone suppression measured by serum testosterone concentrations ≤1 ng/dL or ≥90% reduction from baseline; mean testosterone reported by timepoint."}
• {"endpoint_text":"- Time to pain progression defined using pain scores from the BPI-SF and opiate analgesic use.","definition_or_measurement_approach":"Time to pain progression defined using Brief Pain Inventory-Short Form (BPI-SF) pain scores together with opiate analgesic use data."}

Methods

• Patient Recruitment and Retention Services (Icon (Lr) Limited) - vendor-managed patient recruitment and retention.
• Recruitment materials for publication: Advocacy Fact Sheet, Flyer, Study Poster, Patient Letter, Brochure, HCP Letter (documented per-country).
• Social media advertising: Facebook Advertisement (documented recruitment material).
• Site-based HCP outreach (HCP letters, HCP fact sheets) and local K1 recruitment arrangements per country.

Poland

Earliest CTIS Part Ii Submission Date

06-10-2025

Latest Decision Or Authorization Date

20-01-2026

Processing Time Days

106

Number Of Sites

4

Number Of Participants

19

Spain

Earliest CTIS Part Ii Submission Date

17-09-2025

Latest Decision Or Authorization Date

15-12-2025

Processing Time Days

89

Number Of Sites

6

Number Of Participants

16

Italy

Earliest CTIS Part Ii Submission Date

18-09-2025

Latest Decision Or Authorization Date

17-12-2025

Processing Time Days

90

Number Of Sites

6

Number Of Participants

19

Germany

Earliest CTIS Part Ii Submission Date

22-09-2025

Latest Decision Or Authorization Date

01-12-2025

Processing Time Days

70

Number Of Sites

3

Number Of Participants

10

France

Earliest CTIS Part Ii Submission Date

09-10-2025

Latest Decision Or Authorization Date

26-11-2025

Processing Time Days

48

Number Of Sites

7

Number Of Participants

25

Primary sponsor

Full Name

Astellas Pharma Global Development Inc.

Organisation Type

Pharmaceutical company

Country Of Registered Address

United States

Contract research organisations

Name

Icon Clinical Research Limited

Responsibilities

Site ID and Site Selection; recruitment support and other clinical research services

Name

Icon (Lr) Limited

Responsibilities

Patient Recruitment and Retention Services

Name

Icon Laboratory Services Inc.

Responsibilities

Local laboratory data management, sample testing and sample management

Name

IQVIA Limited

Responsibilities

Subject number allocation, enrollment, dispensation and inventory management

Name

Medidata Solutions Inc.

Responsibilities

Provision of eClinical platform / data services

Third parties

• {"country":"United States","full_name":"Icon Laboratory Services Inc.","duties_or_roles":"Local Labs data. Local laboratory data collected will be managed, queried, and transcribed by ICON Laboratory Services.","organisation_type":"Laboratory/Research/Testing facility"}
• {"country":"Ireland","full_name":"Icon (Lr) Limited","duties_or_roles":"Patient Recruitment and Retention Services","organisation_type":"Non-Pharmaceutical company"}
• {"country":"United States","full_name":"Perceptive Informatics Inc.","duties_or_roles":"Medical Imaging","organisation_type":"Pharmaceutical company"}
• {"country":"United States","full_name":"Icon Laboratory Services Inc.","duties_or_roles":"Sample Testing/Sample Management","organisation_type":"Laboratory/Research/Testing facility"}
• {"country":"United States","full_name":"Eresearchtechnology Inc.","duties_or_roles":"eCOA E-data Capture","organisation_type":"Pharmaceutical company"}
• {"country":"United Kingdom (Northern Ireland)","full_name":"Almac Clinical Services Limited","duties_or_roles":"IP Labeling & Packaging; IP Storage, Distribution, & Returns Management","organisation_type":"Pharmaceutical company"}
• {"country":"Ireland","full_name":"Icon Clinical Research Limited","duties_or_roles":"Site ID and Site Selection","organisation_type":"Pharmaceutical company"}
• {"country":"United Kingdom","full_name":"IQVIA Limited","duties_or_roles":"Subject number allocation, enrollment, dispensation and inventory management; other IRT services","organisation_type":"Pharmaceutical company"}
• {"country":"Ireland","full_name":"Icon Clinical Research Limited","duties_or_roles":"translation services","organisation_type":"Pharmaceutical company"}
• {"country":"United States","full_name":"Medidata Solutions Inc.","duties_or_roles":"Data management / eClinical systems (assigned code 7)","organisation_type":"Non-Pharmaceutical company"}
• {"country":"Netherlands","full_name":"Emsere B.V.","duties_or_roles":"Equipment and ancillary supply provisioning","organisation_type":"Pharmaceutical company"}