Inclusion Criteria:
1. Prostate cancer patients with:
* suspected metastasis who are candidates for initial definitive therapy
* suspected recurrence based on elevated serum prostate-specific antigen (PSA) level (i.e., a progressive and confirmed serum PSA level \> 0.2 ng/mL)
* metastatic disease who might be candidates for treatment with 177Lu-labelled PSMA ligands. (Note: patients with a negative PSMA-PET/CT or discordant PSMA-PET and FDG-PET findings are eligible for this study, providing that they have a histologically confirmed diagnosis of prostate cancer)
2. Subjects able to father children must agree to practice effective contraception for three months starting from the study drug administration.
3. Age ≥ 18
4. ECOG ≤ 1
5. Patient must not have any concomitant infections or active concomitant disease.
6. All acute toxic effects (excluding alopecia and fatigue) of any prior therapy (including surgery, radiation therapy, chemotherapy) must have resolved to National Cancer Institute (NCI) Common Terminology Criteria for Adverse Events (CTCAE) (v. 6.0) Grade ≤ 1.
7. Life expectancy of more than 12 weeks.
8. Ability to undergo imaging study procedures.
9. Evidence of a personally signed and dated informed consent document indicating that the subject has been informed of all pertinent aspects of the study.
10. Willingness and ability to comply with the scheduled visits, plan, laboratory tests and other study procedures.
Exclusion Criteria:
1. Chronically impaired renal function as expressed by creatinine clearance \< 60 mL/min or serum creatinine \> 1.5 x ULN. Note: it is sufficient to evaluate either creatinine clearance or serum creatinine
2. Presence of active hepatitis.
3. Presence of significant cardiac disorders (congestive heart failure, NYHA class III-IV, myocardial infarction within one year prior to study entry, uncontrolled hypertension, or arrhythmia).
4. Any concomitant condition which in the opinion of investigators makes it undesirable for the patient to participate in the study or which could jeopardize compliance with the protocol.
5. Major trauma including major surgery (such as abdominal/cardiac/thoracic surgery) within 4 weeks of administration of the study drug. Minimally invasive procedures such as biopsies are not considered as exclusion criteria.
6. Serious, non-healing wound, ulcer, or bone fracture.
7. Allergy to study medication or excipients in study medication.
8. Any anti-cancer therapy (e.g., cytotoxic chemotherapy, immunotherapy, radiation, surgery, etc.) within 3 weeks before \[68Ga\]Ga-OncoACP3-PET/CT scan.
9. Subject has received, or is scheduled to receive, another investigational medicinal product (IMP) from one month before \[68Ga\]Ga-OncoACP3 injection to end of study participation.
