This phase 2a study will involve enrolment of men presenting with progression of biopsy proven prostate cancer who require imaging for staging/re-staging of their disease. The participants enrolled will be further sub-stratified into two groups; one group of men with hormone-sensitive disease (cohort A), and a second group of men with castrate-resistant disease being considered for 177Lu-PSMA-617 therapy (Cohort B).

This phase 2a study will involve enrolment of men presenting with progression of biopsy proven prostate cancer who require imaging for staging/re-staging of their disease. The participants enrolled will be further sub-stratified into two groups; one group of men with hormone-sensitive disease (cohort A), and a second group of men with castrate-resistant disease being considered for 177Lu-PSMA-617 therapy (Cohort B).

The study will involve men who are being staged or re-staged for metastatic prostate cancer by their treating doctor. The treating doctor will refer the patient to the nuclear medicine department at St. Vincent's Hospital, Sydney for study enrolment.

Screening and D0 visits will be combined for this study. Standard of care bloods (haematology, biochemistry, eGFR and PSA) will be collected at screening/D0 if the results are not already available from the treating doctor. Prior 68Ga-PSMA-11 PET scan within 3 months will be collected from the treating doctor. The PI will ensure that the bloods and 68Ga-PSMA-11 PET scan are reviewed to establish final eligibility before participant undergoes 64Cu-SAR-BBN injection (200mbq) and imaging.

After screening/Day 0 visit, the participant will undergo two imaging scans at 1 hour and 3 hours after having 64Cu-SAR-BBN administration. Total lesional assessment will be calculated with MIM Encore 6.8.7 (MIM Software, Cleveland) using data from the above time points. Safety assessment will be conducted once the participant is enrolled in the study at screening/Day 0 and 48 hours post 3 hours scan by phone call. All adverse events will be recorded on a case report form as source documentation.

Inclusion Criteria:

• Ability to provide informed consent documentation indicating that they understand the purpose and procedures required for the study, and are willing to participate in the study;
• Male patients 18 years or above with hormone sensitive disease, who demonstrate rising PSA levels (>0.2ng/ml) following definitive therapy and a negative 68Ga-PSMA-11 PET scan (defined as SUV max < 3);
• Male patients with metastatic castration resistant prostate cancer being considered for 177Lu-PSMA-617 therapy, with known metastatic disease on conventional imaging and sites with low PSMA expression on 68Ga-PSMA-11 PET scan (defined as SUV max <10) in the presence of disease volume of > 1cm.

Exclusion Criteria:

• Significant inter-current acute illness including (but not limited to) requiring the use of intravenous antibiotics, illness associated with any signs of haemodynamic instability, or illness as determined by trial investigators that warrant other emergent treatment;
• ECOG status higher than 2;
• Major surgery (any procedure requiring general anaesthesia) within 6 weeks prior to screening visit;
• History of significant active cancers requiring treatment other than prostate cancer as per Investigator discretion;
• Any other reason that the investigator considers that would make the patient unsuitable to participate in the study.
• eGFR < 40 mL/min/1.73m2