A Study to Evaluate the Safety and Dosimetry of 68Ga-OncoACP3 in Patients With Prostate Cancer

The Acid Phosphatase 3 (ACP3) is expressed in primary and metastatic prostate cancer lesions. OncoACP3 is a new ligand for ACP3. This is a phase I, multicenter clinical trial to evaluate the safety, dosimetry and biodistribution of \[68Ga\]Ga-OncoACP3 as a PET radiotracer for the diagnostic imaging of prostate cancer. In this trial, 68Ga-OncoACP3 is offered to prostate cancer patients who already received standard of care imaging and might therefore complement available modalities. Eligible patients for this trial are prostate cancer patients, aged 18 years or more 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 All patients will undergo PET/CT imaging with \[68Ga\]Ga-OncoACP3. Patients are divided into two cohorts: * Cohort A: 5 male patients without visceral or bone metastases, which would interfere with dosimetry evaluation of healthy organs. * Cohort B: all patients who meet the eligibility criteria (up to 15 patients) Both cohorts are recruited in parallel, and patients are assigned to the respective cohort based on their disease extent. Whenever possible, patients are enrolled in cohort A, unless they are unsuitable for cohort A, or the required number of patients has already been enrolled in cohort A. All patients will receive a single intravenous bolus administration of \[68Ga\]Ga-OncoACP3 and biodistribution, PK, and dosimetry of \[68Ga\]Ga-OncoACP3 will be assessed based on a series of PET/CT scans, blood and urine sampling. Full dosimetry evaluations will be performed for all patients in cohort A. Dosimetry in the other patients may be performed to the extent that it is possible based on their disease burden (i.e., only organs not affected by malignant lesions can be evaluated), as appropriate. All patients will be assessed for safety. In addition, relative uptake to appropriate reference tissue of \[68Ga\]Ga-OncoACP3 as well as semiquantitative parameters such as SUVmax/SUVmean/SUVsd, are determined. The correlation of \[68Ga\]Ga-OncoACP3 uptake with immunopathology staining for ACP3 will be evaluated in patients undergoing surgery or tumor biopsy collection. For patients who undergo PSMA-PET/CT within 4 weeks before or after the \[68Ga\]Ga-OncoACP3-PET/CT scan, the lesion detection rate will be compared Full dosimetry evaluations will be performed for all patients in cohort A. Additional dosimetry in the other patients may be performed to the extent that it is possible based on their disease burden (i.e., only organs not affected by malignant lesions can be evaluated).