The Present Study Aims to Compare Patients Who Receive the Investigational Product (177Lu-DOTA-rosopatamab) Plus Standard of Care, in Comparison to Standard of Care Only

Inclusion Criteria:

1. Be a male, at least 18 years old, with metastatic adenocarcinoma of the prostatedefined by histological / pathological confirmation of PC.

2. Be of ECOG Performance Status 0, 1, or 2 and have an estimated life expectancy of ≥6months.

3. Have metastatic disease (≥1 metastatic lesions present on baseline CT, MRI, or bonescan imaging).

4. Have castration-resistant PC (defined as disease progressing despite castration byorchiectomy or ongoing use of luteinizing hormone-releasing hormone [LHRH]) and musthave a castrate level of serum/plasma testosterone (<50 ng/dL or <1.7 nmol/L).

5. In the mCRPC setting, must have received a minimum of 12 weeks of prior therapy witha NAAD, either enzalutamide or abiraterone plus prednisone.

6. Should have received one line of prior taxane therapy or have refused or beineligible for taxanes

7. Have a disease that is progressing at study entry, despite a castrate testosteronelevel (<50 ng/dL or <1.7 nmol/L), by the demonstration of at least one of thefollowing:

8. Rising PSA values done in sequence at least 1 week apart and with a minimalstarting value of 2.0 ng/mL.

9. Progressive disease or new lesion(s) in the viscera or lymph nodes as perRECIST1.1 or in bone as per Prostate Cancer Working Group 3 [PCWG3; Scher etal., 2016]). Any ambiguous results are to be confirmed by other imagingmodality (e.g., CT or MRI scan).

10. Have disease that is PSMA positive, as demonstrated by a 68Ga-PSMA11 PET/CT scan andconfirmed as eligible by the Sponsor's central reader (patient must have at leastone site of metastatic disease with SUVmax ≥1.5 times the SUV of normal liver). Ifthe disease meets the criteria for PSMA positivity, but there is one or more softtissue lesion of ≥ 2 cm that is not PSMA positive, then the patient is to beexcluded on the grounds that there is substantial disease which might not respond tothe therapy.

11. Must have recovered to ≤ Grade 2 from all clinically significant toxicities relatedto prior therapies (i.e., surgery, local radiotherapy, NAAD, chemotherapy, etc.).

12. Can be receiving a bisphosphonate or denosumab regimen provided that the patient hasbeen receiving and tolerating this treatment for ≥30 days prior to randomization.

13. Have adequate organ function at Screening: a. Bone marrow: i. Platelets ≥150×109/L. ii. Absolute neutrophil count >1.5×109/L.iii. Hemoglobin ≥10g/dL (no red blood cell transfusion in the previous 4 weeks). b. Liver function: i. Total bilirubin < 1.5×the upper limit of normal (ULN). Forpatients with known Gilbert's Syndrome <3×ULN is permitted. ii. Alanineaminotransferase (ALT) or aspartate aminotransferase (AST) <3×ULN OR <5×ULN forpatients with liver metastases. c. Renal function: i. Serum/plasma creatinine <1.5×ULN or creatinine clearance ≥50 mL/min determined using the Cockcroft & Gaultformula.

14. Have the capacity to understand the study and be able and willing to comply with allprotocol requirements.

15. Patients must comply with the radiation protection rules (including hospitaladmissions and isolation) that are used by the treating institution in order toprotect their contacts and the general public, especially if a female partner of thepatient is or could be pregnant.

16. Must agree to practice adequate precautions to prevent pregnancy in a partner and toavoid potential problems associated with radiation exposure to the unborn child (Refer to Clinical Trials Facilitation Group, 2020: Recommendations related tocontraception and pregnancy testing in clinical trials Version 1.1, CTFG, 2020).

Exclusion Criteria:

1. Are unable to understand or are unwilling to sign a written informed consentdocument or to follow investigational procedures in the opinion of the Investigator.

2. Have PC associated with pathological findings consistent with small cell or anyhistology other than adenocarcinoma of the prostate. If there are minor elements ofneuroendocrine histology, this is acceptable.

3. Uncontrolled pain.

4. Diagnosed with other malignancies that are expected to alter life expectancy or mayinterfere with disease assessment. However, patients with a prior history ofmalignancy that has been adequately treated and who have been disease-free for morethan 3 years are eligible, as are patients with adequately treated non-melanoma skincancer, and superficial bladder cancer.

5. Are at increased risk of hemorrhage or bleeding, or with a recent history of athrombolytic event (e.g., deep vein thrombosis [DVT]/ pulmonary embolism [PE]) andhave been administered long-term anti-coagulant or anti-platelet agents.

6. Have received prior treatment with monoclonal antibody (mAb) J591 or HuJ591 or anyother PSMA targeted therapy.

7. Have known allergies, hypersensitivity, or intolerance to the investigational drugor its excipients.

8. Have received prior systemic anti-cancer therapy (e.g., chemotherapy, immunotherapy,or biological therapy) and/or radiation therapy within 4 weeks of randomization ORif any significant AEs have not resolved to National Cancer Institute (NCI) AECriteria ≤2; OR are receiving other concurrent cytotoxic chemotherapy,immunotherapy, radioligand therapy, or investigational therapy.

9. Have received prior treatment with radioisotopes, including but not limited to: 89Strontium, 153Samarium, 186Rhenium, 188Rhenium, 223Radium, or hemi-bodyirradiation within 6 months prior to randomization.

10. Have received other investigational therapy within 4 weeks of randomization.

11. Have known brain metastases or hepatic metastases.

12. Have a history of seizure and/or stroke within past 6 months.

13. Have clinical or radiologic findings indicative of impending cord compression orexperience symptomatic cord compression.

14. Have a serious active or sub-clinical infection or angina pectoris (New York HeartAssociation [NYHA] Class III or IV), significantly prolonged QT interval or otherserious illness(es) involving the cardiac, respiratory, central nervous system,renal, hepatic or hematological organ systems, which might impair the ability tocomplete this study or could interfere with determination of causality of anyadverse effects experienced in this study, or which require treatment that couldinteract with study treatment, particularly with enzalutamide.

15. Have received treatment with any PARP inhibitors (i.e., Olaparib) or with anyplatinum based anti-neoplastic drugs.

16. Have a known alteration in breast cancer genes (BRCA) BRCA1, BRCA2, or AtaxiaTelangiectasia Mutated Gene (ATM) gene and are eligible to receive Olaparib therapyaccording to their institution's SoC