318 Background: Prostate cancer (PC) is the second most frequent malignancy in men worldwide. 68Ga-PSMA-11 is one of the most widely used radiotracers for positron emission tomography (PET) of prostate-specific membrane antigen (PSMA) positive lesions in men with PC and is part of standard clinical practice at many centres. Due to the longer half-life and shorter positron range of copper-64 (t1/2=12.7 hours; mean positron range=0.56 mm), a novel PSMA-targeting radiotracer labelled with this radionuclide, 64Cu-SAR-bisPSMA, has the potential to provide advantages over 68Ga-PSMA-11 (t1/2=68 minutes; mean positron range=3.5 mm). The 12.7 hour half-life of Cu-64 allows the central manufacturing of 64Cu-SAR-bisPSMA with a product shelf-life of up to 2 days. The longer half-life enables PET imaging from 1 to 72 hours after administration which offers greater flexibility in terms of scheduling of patients and may translate into detection of additional lesions due to increased Standardized Uptake Values (SUV) in the lesions relative to background following biological clearance of the tracer from organs over time. The shorter positron range may lead to improved resolution on the scan and thus, better detection of small lesions, including those that are in close proximity to each other, or to organs involved in clearance of the product such as the bladder and kidneys. In addition to the potential imaging and supply benefits of Cu-64, current generation PSMA targeting agents such as 68Ga-PSMA-11 have only a single targeting functional group. 64Cu-SAR-bisPSMA has two PSMA-targeting functional groups, which can lead to improved tumor uptake and retention. This was shown in a preclinical study, where 64Cu-SAR-bisPSMA outperformed the monomeric 64Cu-SAR-PSMA with respect to both tumor uptake and retention (Zia et al, 2019). Methods: Patients with untreated, histopathology-proven, intermediate- to high-risk PC, planned for radical prostatectomy underwent 68Ga-PSMA-11 PET/CT per institutional practice and were subsequently allocated to 1 out of 3 dose cohorts (1:1:3) to receive either 100 MBq, 150 MBq or 200 MBq of 64Cu-SAR-bisPSMA, respectively. A PET/CT was acquired at 3-hours (±1 hour) post-injection of 64Cu-SAR-bisPSMA. Two independent, blinded, central readers assessed the detection of primary PC on the 200 MBq 64Cu-SAR-bisPSMA PET/CTs as the primary endpoint. To compare the intensity of lesions on 68Ga-PSMA-11 and 64Cu-SAR-bisPSMA PET, both readers determined the SUVs (SUVmax, SUVmean) and tumour-to-background ratio (ratio of lesion SUVmax and background SUVmean) in up to 5 concordant lesions between 68Ga-PSMA-11 and 64Cu-SAR-bisPSMA PET/CT as an exploratory endpoint. Clinical trial information: NCT04839367 .