This clinical trial is an open-label, single-arm, multi-center, escalation (Phase 1 Part B only), rater-blind (Phase 2 only), phase 1/2 trial to evaluate the diagnostic validity/safety of Ga-68-NGUL and efficacy/safety of Lu-177-DGUL on the anti-tumor activity that aims to simultaneously evaluate diagnostic and therapeutic validity.

Inclusion Criteria:

• Male patients of 19 years or older
• Patients with metastatic diseases due to adenocarcinoma of the prostate as confirmed
• Patients whose blood testosterone levels at the screening visit meet the castration criteria(< 50 ng/dL)
• Patients with advanced metastatic castration-resistant prostate cancer who have failed standard treatment or no longer have standard treatment available
• Those who are maintaining androgen deprivation therapy (ADT) regardless of the type
• Patients receiving bone resorption treatment who have maintained a stable dose for at least 4 weeks prior to baseline
• Patients with positive lesions on Ga-68-NGUL PET scan
• Patients with Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2
• Patients with an expected survival of 6months or more
• Patients with confirmed adequate hematological function, renal and hepatic function according to the following criteria
• Patients who have voluntarily consented to participate in this clinical trial and signed the informed consent form

Exclusion Criteria:

• Patients with hematologic malignancy, including lymphoma and solid cancers other than prostate cancer, within 3 years prior to baseline
• Patients who have received chemotherapy, biotherapy, or immunotherapy for prostate cancer treatment within 4 weeks prior to baseline
• Patients who have received radiation chemotherapy or radiation therapy within 12 weeks prior to baseline
• Patients who have received high-dose chemotherapy requiring hematopoietic stem cell therapy within 2 years prior to baseline
• Those who had previously received PSMA-targeted treatment or received radiopharmaceutical treatment, such as radium-223, within 6 months prior to baseline
• Patients with symptomatic central nervous system metastases
• Patients with unsuitable medical history or surgical/procedural history
• Patients with severe drug hypersensitivity and a history of hypersensitivity to the investigational product and similar drugs
• Patients receiving concomitant nephrotoxic drugs
• Patients with severe claustrophobia that is not controlled with anti-anxiety medications
• Patients with hypersensitivity reactions to components of the investigational product
• If the partner is a female of childbearing potential, patients who do not intend to abstain from abstinence or use appropriate contraceptive methods for at least 3 months after the end of the clinical trial period and investigational product administration
• Patients who have been administered with other investigational products or treated with clinical investigational devices within 4 weeks prior to baseline
• Patients who cannot participate in the clinical trial as determined by other investigators