Phase I Clinical Trial of Prostate-Specific Membrane Antigen-Targeting⁶⁸Ga-NGUL PET/CT in Healthy Volunteers and Patients with Prostate Cancer

Objective:⁶⁸Ga-NGUL is a novel prostate-specific membrane antigen (PSMA)-targeting tracer based on Glu-Urea-Lys derivatives conjugated to a 1,4,7-triazacyclononane-N,N’,N’’-triacetic acid (NOTA) chelator via a thiourea-type short linker. This phase I clinical trial of⁶⁸Ga-NGUL was conducted to evaluate the safety and radiation dosimetry of⁶⁸Ga-NGUL in healthy volunteers and the lesion detection rate of⁶⁸Ga-NGUL in patients with prostate cancer. Materials and Methods: We designed a prospective, open-label, single-arm clinical trial with two cohorts comprising six healthy adult men and six patients with metastatic prostate cancer. Safety and blood test-based toxicities were monitored throughout the study. PET/CT scans were acquired at multiple time points after administering⁶⁸Ga-NGUL (2 MBq/kg; 96–165 MBq). In healthy adults, absorbed organ doses and effective doses were calculated using the OLINDA/EXM software. In patients with prostate cancer, the rates of detecting suspicious lesions by⁶⁸Ga-NGUL PET/CT and conventional imaging (CT and bone scintigraphy) during the screening period, within one month after recruitment, were compared. Results: All 12 participants (six healthy adults aged 31–32 years and six prostate cancer patients aged 57–81 years) completed the clinical trial. No drug-related adverse events were observed. In the healthy adult group,⁶⁸Ga-NGUL was rapidly distributed, with the highest uptake in the kidneys. The median effective dose coefficient was calculated as 0.025 mSv/MBq, and cumulative activity in the bladder had the highest contribution. In patients with metastatic prostate cancer, 229 suspicious lesions were detected using either⁶⁸Ga-NGUL PET/CT or conventional imaging. Among them,⁶⁸Ga-NGUL PET/CT detected 199 (86.9%) lesions and CT or bone scintigraphy detected 114 (49.8%) lesions. Conclusion:⁶⁸Ga-NGUL can be safely applied clinically and has shown a higher detection rate for the localization of metastatic lesions in prostate cancer than conventional imaging. Therefore,⁶⁸Ga-NGUL is a valuable option for prostate cancer imaging.