The overexpression of urokinase-type plasminogen activator receptors (uPARs) represents an established biomarker for aggressiveness in most common malignant diseases, including breast cancer (BC), prostate cancer (PC), and urinary bladder cancer (UBC), and is therefore an important target for new cancer therapeutic and diagnostic strategies. In this study, uPAR PET imaging using a68Ga-labeled version of the uPAR-targeting peptide (AE105) was investigated in a group of patients with BC, PC, and UBC. The aim of this first-in-human, phase I clinical trial was to investigate the safety and biodistribution in normal tissues and uptake in tumor lesions.Methods:Ten patients (6 PC, 2 BC, and 2 UBC) received a single intravenous dose of68Ga-NOTA-AE105 (154 ± 59 MBq; range, 48-208 MBq). The biodistribution and radiation dosimetry were assessed by serial whole-body PET/CT scans (10 min, 1 h, and 2 h after injection). Safety assessment included measurements of vital signs with regular intervals during the imaging sessions and laboratory blood screening tests performed before and after injection. In a subgroup of patients, the in vivo stability of68Ga-NOTA-AE105 was determined in collected blood and urine. PET images were visually analyzed for visible tumor uptake of68Ga-NOTA-AE105, and SUVs were obtained from tumor lesions by manually drawing volumes of interest in the malignant tissue.Results:No adverse events or clinically detectable pharmacologic effects were found. The radioligand exhibited good in vivo stability and fast clearance from tissue compartments primarily by renal excretion. The effective dose was 0.015 mSv/MBq, leading to a radiation burden of 3 mSv when the clinical target dose of 200 MBq was used. In addition, radioligand accumulation was seen in primary tumor lesions as well as in metastases.Conclusion:This first-in-human, phase I clinical trial demonstrates the safe use and clinical potential of68Ga-NOTA-AE105 as a new radioligand for uPAR PET imaging in cancer patients.