Mice were anesthetized and imaged 60 min post-administration using a small pet PET scanner (Focus 120, Siemens, Knoxville, TN). [68Ga]DP11. Uptake of [68Ga]DP11 (60 min) and [67Ga]DP11 (24 h) in PC3-PIP tumors was 12. 37 4. 19 %ID/g and 12. 49 6. 88 %ID/g, respectively; [68Ga]DP11 was 13. 83 a few. 77 and 17. 76 1 . 84 on same-day and 15. 98 5. 82 %ID/g on second-day imaging. == Conclusions == This study demonstrates that [68Ga]DP11, in a given PSMA+ lesion, is constant under several same-day or serial-day imaging CZ415 conditions. Keywords: Gallium-68, PSMA, prostate cancer, repeatability, positron emission tomography, mice, specific activity == Intro == Prostate cancer (PCa) is the second most lethal cancer among men in the U. H. with 26, 120 estimated deaths in 2016 [1]. To address this problem, significant advances have been made in diagnostic imaging, which have aimed to characterize primary prostatic lesions, correlate with the clinical state of disease, and monitor response to therapy [2]. The current standard-of-care imaging, however , cannot adequately monitor the propagate of disease from the primary site to regional lymph nodes and distant metastatic sites or annotate the genomic evolution of disease during this process. As the detection of metastatic lesions and propagate is crucial intended for the staging, management, and disease-specific survival of prostate cancer, an imaging biomarker-based solution appears necessary. Prostate-specific membrane antigen (PSMA) is a candidate antigen on which to target a biomarker-based strategy. It is an extracellular glutamate carboxypeptidase II and a zinc metalloenzyme that catalyzes the hydrolysis of C-terminal glutamate in peptides. More importantly, it is highly expressed in both primary and metastatic prostate cancer lesions, correlating with CZ415 the stage/grade of the PCa [3]. PSMA was originally detected in the androgen-dependent prostate cancer cell collection LNCaP and was thought to be confined to prostate tumors, but subsequent studies have revealed that PSMA is expressed in the neovasculature of many other tumors [4]. Regardless, this relative selectivity still makes PSMA a very attractive target for developing targeted imaging and therapeutic agents. Accordingly, several biological vectors including antibodies [5], peptides [6], small molecules, and particles have been developed and evaluated as potential carriers intended for imaging and therapeutic entities. Urea-glutamate-based small molecule antagonist probes have recently gained favor among other alternatives, as their molecular weight, ease of labeling, fast clearance, and ability to label with short-lived isotopes (e. g., Ga-68 and F-18) permit repetitive imaging. A variety of Positron CZ415 Emission Tomography (PET)/Single Photon Emission Computed Tompgrahy probes using Rabbit Polyclonal to CKLF2 I-123, Ga-68, and F-18 have been developed and evaluated in both preclinical and clinical settings [712]. Recently, [68Ga]DKFZ11-PSMA developed by Eder and colleagues [13] offers gained significant popularity due to its ease of labeling and excellent performancein vivoin detecting both primary and metastatic prostate cancer lesions. The tracer demonstrated 100% sensitivity and specificity in a cohort study of 319 patients [14]. These studies indicate that [68Ga]DKFZ11-PSMA ([68Ga]DP11) offers true potential to be used globally for detecting prostate cancer in patient populations. Ga-68 is a PET isotope and therefore [68Ga]DP11 has the potential to quantify receptor density on each individual lesion. The theoretical maximum specific activity (SA) of Ga-68 centered radiopharmaceuticals is approximately 2764 Ci/mol. CZ415 However , with the current synthetic protocols utilized in clinical production, the typical apparent CZ415 SAs (e. g., [68Ga]DP11 + free DKFZ11-PSMA or [68Ga]DOTA-TOC + DOTA-TOC, etc . ) are closer to 0. 51 Ci/mol due to the presence of uncomplexed peptide. This translates to about 510 nmoles for each patient for a 10 mCi dose. Due to the large amount of ligand administered during scanning, it is possible that the ligand can residualize around the receptors and affect the quantification on the subsequent scan. With increasing use of [68Ga]DP11 as a scouting scan for treatment with [177Lu]DKFZ-PSMA-617 [15] or [225Ac]DKFZ-PSMA-617 [16], it is important to understand the effect of prior imaging with [68Ga]DP11 (if any) on the uptake of the therapeutic radiopharmaceutical. While many studies have focused on optimizing the radiosynthesis and findings on the ability to detect lesions in patient populations using [68Ga]DP11 have been published, up to now none from the studies have addressed the question of reproducibility of scans. For a receptor-targeted radiopharmaceutical, residual activity can impact the subsequent scan. This is important if PSMA-based imaging is being used for measuring response to therapy on a routine basis [17]. This is also important for PSMA-targeted therapeutic methods that leverage these urea-glutamate-based small molecules for delivering toxins or therapeutic radionuclides [18], as receptor availability is one of the critical limiting factors. In the current manuscript, we have addressed using PSMA-expressing PC3-PIP xenografts, specifically whether imaging these tumors with [68Ga]DP11 affects subsequent serial scans performed at 24 and 48 h. == Materials and Methods == All starting materials, solvents, and reagents were purchased from commercial sources (Sigma-Aldrich, St . Louis, MO and Thermo Fisher Scientific, Waltham, MA) and used without further purification. The.