@article{ChenHiranoWerneretal.2018, author = {Chen, Xinyu and Hirano, Mitsuru and Werner, Rudolf A. and Decker, Michael and Higuchi, Takahiro}, title = {Novel \(^{18}\)F-labeled PET Imaging Agent FV45 targeting the Renin-Angiotensin System}, series = {ACS Omega}, volume = {3}, journal = {ACS Omega}, number = {9}, issn = {2470-1343}, doi = {10.1021/acsomega.8b01885}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-167144}, pages = {10460-10470}, year = {2018}, abstract = {Renin-angiotensin system (RAS) plays an important role in the regulation of blood pressure and hormonal balance. Using positron emission tomography (PET) technology, it is possible to monitor the physiological and pathological distribution of angiotensin II type 1 receptors (AT\(_1\)), which reflects the functionality of RAS. A new \(^{18}\)F-labeled PET tracer derived from the clinically used AT\(_1\) antagonist valsartan showing the least possible chemical alteration from the valsartan structure has been designed and synthesized with several strategies, which can be applied for the syntheses of further derivatives. Radioligand binding study showed that the cold reference FV45 (K\(_i\) 14.6 nM) has almost equivalent binding affinity as its lead valsartan (K\(_i\) 11.8 nM) and angiotensin II (K\(_i\) 1.7 nM). Successful radiolabeling of FV45 in a one-pot radiofluorination followed by the deprotection procedure with 21.8 ± 8.5\% radiochemical yield and >99\% radiochemical purity (n = 5) enabled a distribution study in rats and opened a path to straightforward large-scale production. A fast and clear kidney uptake could be observed, and this renal uptake could be selectively blocked by pretreatment with AT\(_1\)-selective antagonist valsartan. Overall, as the first \(^{18}\)F-labeled PET tracer based on a derivation from clinically used drug valsartan with almost identical chemical structure, [\(^{18}\)F]FV45 will be a new tool for assessing the RAS function by visualizing AT\(_i\) receptor distributions and providing further information regarding cardiovascular system malfunction as well as possible applications in inflammation research and cancer diagnosis.}, subject = {Positronen-Emissions-Tomografie}, language = {en} } @article{ChenKudoLapaetal.2020, author = {Chen, Xinyu and Kudo, Takashi and Lapa, Constantin and Buck, Andreas and Higuchi, Takahiro}, title = {Recent advances in radiotracers targeting norepinephrine transporter: structural development and radiolabeling improvements}, series = {Journal of Neural Transmission}, volume = {127}, journal = {Journal of Neural Transmission}, doi = {10.1007/s00702-020-02180-4}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-241148}, pages = {851-873}, year = {2020}, abstract = {The norepinephrine transporter (NET) is a major target for the evaluation of the cardiac sympathetic nerve system in patients with heart failure and Parkinson's disease. It is also used in the therapeutic applications against certain types of neuroendocrine tumors, as exemplified by the clinically used \(^{123/131}\)I-MIBG as theranostic single-photon emission computed tomography (SPECT) agent. With the development of more advanced positron emission tomography (PET) technology, more radiotracers targeting NET have been reported, with superior temporal and spatial resolutions, along with the possibility of functional and kinetic analysis. More recently, fluorine-18-labelled NET tracers have drawn increasing attentions from researchers, due to their longer radiological half-life relative to carbon-11 (110 min vs. 20 min), reduced dependence on on-site cyclotrons, and flexibility in the design of novel tracer structures. In the heart, certain NET tracers provide integral diagnostic information on sympathetic innervation and the nerve status. In the central nervous system, such radiotracers can reveal NET distribution and density in pathological conditions. Most radiotracers targeting cardiac NET-function for the cardiac application consistent of derivatives of either norepinephrine or MIBG with its benzylguanidine core structure, e.g. \(^{11}\)C-HED and \(^{18}\)F-LMI1195. In contrast, all NET tracers used in central nervous system applications are derived from clinically used antidepressants. Lastly, possible applications of NET as selective tracers over organic cation transporters (OCTs) in the kidneys and other organs controlled by sympathetic nervous system will also be discussed.}, language = {en} } @article{ChenWernerJavadietal.2015, author = {Chen, Xinyu and Werner, Rudolf A. and Javadi, Mehrbod S. and Maya, Yoshifumi and Decker, Michael and Lapa, Constantin and Herrmann, Ken and Higuchi, Takahiro}, title = {Radionuclide imaging of neurohormonal system of the heart}, series = {Theranostics}, volume = {5}, journal = {Theranostics}, number = {6}, doi = {10.7150/thno.10900}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-149205}, pages = {545-558}, year = {2015}, abstract = {Heart failure is one of the growing causes of death especially in developed countries due to longer life expectancy. Although many pharmacological and instrumental therapeutic approaches have been introduced for prevention and treatment of heart failure, there are still limitations and challenges. Nuclear cardiology has experienced rapid growth in the last few decades, in particular the application of single photon emission computed tomography (SPECT) and positron emission tomography (PET), which allow non-invasive functional assessment of cardiac condition including neurohormonal systems involved in heart failure; its application has dramatically improved the capacity for fundamental research and clinical diagnosis. In this article, we review the current status of applying radionuclide technology in non-invasive imaging of neurohormonal system in the heart, especially focusing on the tracers that are currently available. A short discussion about disadvantages and perspectives is also included.}, language = {en} } @article{ChenWernerKoshinoetal.2022, author = {Chen, Xinyu and Werner, Rudolf A. and Koshino, Kazuhiro and Nose, Naoko and M{\"u}hlig, Saskia and Rowe, Steven P. and Pomper, Martin G. and Lapa, Constantin and Decker, Michael and Higuchi, Takahiro}, title = {Molecular Imaging-Derived Biomarker of Cardiac Nerve Integrity - Introducing High NET Affinity PET Probe \(^{18}\)F-AF78}, series = {Theranostics}, volume = {12}, journal = {Theranostics}, number = {9}, doi = {10.7150/thno.63205}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-300685}, pages = {4446 -- 4458}, year = {2022}, abstract = {Background: Radiolabeled agents that are substrates for the norepinephrine transporter (NET) can be used to quantify cardiac sympathetic nervous conditions and have been demonstrated to identify high-risk congestive heart failure (HF) patients prone to arrhythmic events. We aimed to fully characterize the kinetic profile of the novel \(^{18}\)F-labeled NET probe AF78 for PET imaging of the cardiac sympathetic nervous system (SNS) among various species. Methods: \(^{18}\)F-AF78 was compared to norepinephrine (NE) and established SNS radiotracers by employing in vitro cell assays, followed by an in vivo PET imaging approach with healthy rats, rabbits and nonhuman primates (NHPs). Additionally, chase protocols were performed in NHPs with NET inhibitor desipramine (DMI) and the NE releasing stimulator tyramine (TYR) to investigate retention kinetics in cardiac SNS. Results: Relative to other SNS radiotracers, 18F-AF78 showed higher transport affinity via NET in a cell-based competitive uptake assay (IC\(^{50}\) 0.42 ± 0.14 µM), almost identical to that of NE (IC\(^{50}\), 0.50 ± 0.16 µM, n.s.). In rabbits and NHPs, initial cardiac uptake was significantly reduced by NET inhibition. Furthermore, cardiac tracer retention was not affected by a DMI chase protocol but was markedly reduced by intermittent TYR chase, thereby suggesting that \(^{18}\)F-AF78 is stored and can be released via the synaptic vesicular turnover process. Computational modeling hypothesized the formation of a T-shaped π-π stacking at the binding site, suggesting a rationale for the high affinity of \(^{18}\)F-AF78. Conclusion: \(^{18}\)F-AF78 demonstrated high in vitro NET affinity and advantageous in vivo radiotracer kinetics across various species, indicating that \(^{18}\)F-AF78 is an SNS imaging agent with strong potential to guide specific interventions in cardiovascular medicine.}, language = {en} } @article{ChenWernerLapaetal.2018, author = {Chen, Xinyu and Werner, Rudolf A. and Lapa, Constantin and Nose, Naoko and Hirano, Mitsuru and Javadi, Mehrbod S. and Robinson, Simon and Higuchi, Takahiro}, title = {Subcellular storage and release mode of the novel \(^{18}\)F-labeled sympathetic nerve PET tracer LMI1195}, series = {EJNMMI Research}, volume = {8}, journal = {EJNMMI Research}, number = {12}, issn = {2191-219X}, doi = {10.1186/s13550-018-0365-9}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-167081}, year = {2018}, abstract = {Background: \(^{18}\)F-N-[3-bromo-4-(3-fluoro-propoxy)-benzyl]-guanidine (\(^{18}\)F-LMI1195) is a new class of PET tracer designed for sympathetic nervous imaging of the heart. The favorable image quality with high and specific neural uptake has been previously demonstrated in animals and humans, but intracellular behavior is not yet fully understood. The aim of the present study is to verify whether it is taken up in storage vesicles and released in company with vesicle turnover. Results: Both vesicle-rich (PC12) and vesicle-poor (SK-N-SH) norepinephrine-expressing cell lines were used for in vitro tracer uptake studies. After 2 h of \(^{18}\)F-LMI1195 preloading into both cell lines, effects of stimulants for storage vesicle turnover (high concentration KCl (100 mM) or reserpine treatment) were measured at 10, 20, and 30 min. \(^{131}\)I-meta-iodobenzylguanidine (\(^{131}\)I-MIBG) served as a reference. Both high concentration KCl and reserpine enhanced \(^{18}\)F-LMI1195 washout from PC12 cells, while tracer retention remained stable in the SK-N-SH cells. After 30 min of treatment, 18F-LMI1195 releasing index (percentage of tracer released from cells) from vesicle-rich PC12 cells achieved significant differences compared to cells without treatment condition. In contrast, such effect could not be observed using vesicle-poor SK-N-SH cell lines. Similar tracer kinetics after KCl or reserpine treatment were also observed using 131I-MIBG. In case of KCl exposure, Ca\(^{2+}\)-free buffer with the calcium chelator, ethylenediaminetetracetic acid (EDTA), could suppress the tracer washout from PC12 cells. This finding is consistent with the tracer release being mediated by Ca\(^{2+}\) influx resulting from membrane depolarization. Conclusions: Analogous to \(^{131}\)I-MIBG, the current in vitro tracer uptake study confirmed that \(^{131}\)F-LMI1195 is also stored in vesicles in PC12 cells and released along with vesicle turnover. Understanding the basic kinetics of \(^{18}\)FLMI1195 at a subcellular level is important for the design of clinical imaging protocols and imaging interpretation.}, subject = {Positronen-Emissions-Tomografie}, language = {en} } @article{EisslerWernerAriasLozaetal.2021, author = {Eissler, Cristoph and Werner, Rudolf A. and Arias-Loza, Paula and Nose, Naoko and Chen, Xinyu and Pomper, Martin G. and Rowe, Steven P. and Lapa, Constantin and Buck, Andreas K. and Higuchi, Takahiro}, title = {The number of frames on ECG-gated \(^{18}\)F-FDG small animal PET has a significant impact on LV systolic and diastolic functional parameters}, series = {Molecular Imaging}, volume = {2021}, journal = {Molecular Imaging}, doi = {10.1155/2021/4629459}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265778}, year = {2021}, abstract = {Objectives. This study is aimed at investigating the impact of frame numbers in preclinical electrocardiogram- (ECG-) gated \(^{18}\)F-fluorodeoxyglucose (\(^{18}\)F-FDG) positron emission tomography (PET) on systolic and diastolic left ventricular (LV) parameters in rats. Methods. \(^{18}\)F-FDG PET imaging using a dedicated small animal PET system with list mode data acquisition and continuous ECG recording was performed in diabetic and control rats. The list-mode data was sorted and reconstructed with different numbers of frames (4, 8, 12, and 16) per cardiac cycle into tomographic images. Using an automatic ventricular edge detection software, left ventricular (LV) functional parameters, including ejection fraction (EF), end-diastolic (EDV), and end-systolic volume (ESV), were calculated. Diastolic variables (time to peak filling (TPF), first third mean filling rate (1/3 FR), and peak filling rate (PFR)) were also assessed. Results. Significant differences in multiple parameters were observed among the reconstructions with different frames per cardiac cycle. EDV significantly increased by numbers of frames (353.8 \& PLUSMN; 57.7 mu l*, 380.8 \& PLUSMN; 57.2 mu l*, 398.0 \& PLUSMN; 63.1 mu l*, and 444.8 \& PLUSMN; 75.3 mu l at 4, 8, 12, and 16 frames, respectively; *P < 0.0001 vs. 16 frames), while systolic (EF) and diastolic (TPF, 1/3 FR and PFR) parameters were not significantly different between 12 and 16 frames. In addition, significant differences between diabetic and control animals in 1/3 FR and PFR in 16 frames per cardiac cycle were observed (P < 0.005), but not for 4, 8, and 12 frames. Conclusions. Using ECG-gated PET in rats, measurements of cardiac function are significantly affected by the frames per cardiac cycle. Therefore, if you are going to compare those functional parameters, a consistent number of frames should be used.}, language = {en} } @article{FroehlichSerflingHiguchietal.2021, author = {Fr{\"o}hlich, Matthias and Serfling, Sebastian and Higuchi, Takahiro and Pomper, Martin G. and Rowe, Steven P. and Schmalzing, Marc and Tony, Hans-Peter and Gernert, Michael and Strunz, Patrick-Pascal and Portegys, Jan and Schwaneck, Eva-Christina and Gadeholt, Ottar and Weich, Alexander and Buck, Andreas K. and Bley, Thorsten A. and Guggenberger, Konstanze V. and Werner, Rudolf A.}, title = {Whole-Body [\(^{18}\)F]FDG PET/CT Can Alter Diagnosis in Patients with Suspected Rheumatic Disease}, series = {Diagnostics}, volume = {11}, journal = {Diagnostics}, number = {11}, issn = {2075-4418}, doi = {10.3390/diagnostics11112073}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-250227}, year = {2021}, abstract = {The 2-deoxy-d-[\(^{18}\)F]fluoro-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) is widely utilized to assess the vascular and articular inflammatory burden of patients with a suspected diagnosis of rheumatic disease. We aimed to elucidate the impact of [\(^{18}\)F]FDG PET/CT on change in initially suspected diagnosis in patients at the time of the scan. Thirty-four patients, who had undergone [\(^{18}\)F]FDG PET/CT, were enrolled and the initially suspected diagnosis prior to [18F]FDG PET/CT was compared to the final diagnosis. In addition, a semi-quantitative analysis including vessel wall-to-liver (VLR) and joint-to-liver (JLR) ratios was also conducted. Prior to [\(^{18}\)F]FDG PET/CT, 22/34 (64.7\%) of patients did not have an established diagnosis, whereas in 7/34 (20.6\%), polymyalgia rheumatica (PMR) was suspected, and in 5/34 (14.7\%), giant cell arteritis (GCA) was suspected by the referring rheumatologists. After [\(^{18}\)F]FDG PET/CT, the diagnosis was GCA in 19/34 (55.9\%), combined GCA and PMR (GCA + PMR) in 9/34 (26.5\%) and PMR in the remaining 6/34 (17.6\%). As such, [\(^{18}\)F]FDG PET/CT altered suspected diagnosis in 28/34 (82.4\%), including in all unclear cases. VLR of patients whose final diagnosis was GCA tended to be significantly higher when compared to VLR in PMR (GCA, 1.01 ± 0.08 (95\%CI, 0.95-1.1) vs. PMR, 0.92 ± 0.1 (95\%CI, 0.85-0.99), p = 0.07), but not when compared to PMR + GCA (1.04 ± 0.14 (95\%CI, 0.95-1.13), p = 1). JLR of individuals finally diagnosed with PMR (0.94 ± 0.16, (95\%CI, 0.83-1.06)), however, was significantly increased relative to JLR in GCA (0.58 ± 0.04 (95\%CI, 0.55-0.61)) and GCA + PMR (0.64 ± 0.09 (95\%CI, 0.57-0.71); p < 0.0001, respectively). In individuals with a suspected diagnosis of rheumatic disease, an inflammatory-directed [\(^{18}\)F]FDG PET/CT can alter diagnosis in the majority of the cases, particularly in subjects who were referred because of diagnostic uncertainty. Semi-quantitative assessment may be helpful in establishing a final diagnosis of PMR, supporting the notion that a quantitative whole-body read-out may be useful in unclear cases.}, language = {en} } @article{GentzschChenSpatzetal.2021, author = {Gentzsch, Christian and Chen, Xinyu and Spatz, Philipp and Košak, Urban and Knez, Damijan and Nose, Naoko and Gobec, Stanislav and Higuchi, Takahiro and Decker, Michael}, title = {Synthesis and Initial Characterization of a Reversible, Selective \(^{18}\)F-Labeled Radiotracer for Human Butyrylcholinesterase}, series = {Molecular Imaging and Biology}, volume = {23}, journal = {Molecular Imaging and Biology}, number = {4}, issn = {1860-2002}, doi = {10.1007/s11307-021-01584-2}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-269870}, pages = {505-515}, year = {2021}, abstract = {Purpose A neuropathological hallmark of Alzheimer's disease (AD) is the presence of amyloid-β (Aβ) plaques in the brain, which are observed in a significant number of cognitively normal, older adults as well. In AD, butyrylcholinesterase (BChE) becomes associated with A\(_{β}\) aggregates, making it a promising target for imaging probes to support diagnosis of AD. In this study, we present the synthesis, radiochemistry, in vitro and preliminary ex and in vivo investigations of a selective, reversible BChE inhibitor as PET-tracer for evaluation as an AD diagnostic. Procedures Radiolabeling of the inhibitor was achieved by fluorination of a respective tosylated precursor using K[\(^{18}\)F]. IC\(_{50}\) values of the fluorinated compound were obtained in a colorimetric assay using recombinant, human (h) BChE. Dissociation constants were determined by measuring hBChE activity in the presence of different concentrations of inhibitor. Results Radiofluorination of the tosylate precursor gave the desired radiotracer in an average radiochemical yield of 20 ± 3 \%. Identity and > 95.5 \% radiochemical purity were confirmed by HPLC and TLC autoradiography. The inhibitory potency determined in Ellman's assay gave an IC\(_{50}\) value of 118.3 ± 19.6 nM. Dissociation constants measured in kinetic experiments revealed lower affinity of the inhibitor for binding to the acylated enzyme (K2 = 68.0 nM) in comparison to the free enzyme (K\(_{1}\) = 32.9 nM). Conclusions The reversibly acting, selective radiotracer is synthetically easily accessible and retains promising activity and binding potential on hBChE. Radiosynthesis with \(^{18}\)F labeling of tosylates was feasible in a reasonable time frame and good radiochemical yield.}, language = {en} } @article{GentzschHoffmannOhshimaetal.2021, author = {Gentzsch, Christian and Hoffmann, Matthias and Ohshima, Yasuhiro and Nose, Naoko and Chen, Xinyu and Higuchi, Takahiro and Decker, Michael}, title = {Synthesis and Initial Characterization of a Selective, Pseudo-irreversible Inhibitor of Human Butyrylcholinesterase as PET Tracer}, series = {ChemMedChem}, volume = {16}, journal = {ChemMedChem}, number = {9}, doi = {10.1002/cmdc.202000942}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-239904}, pages = {1427 -- 1437}, year = {2021}, abstract = {The enzyme butyrylcholinesterase (BChE) represents a promising target for imaging probes to potentially enable early diagnosis of neurodegenerative diseases like Alzheimer's disease (AD) and to monitor disease progression in some forms of cancer. In this study, we present the design, facile synthesis, in vitro and preliminary ex vivo and in vivo evaluation of a morpholine-based, selective inhibitor of human BChE as a positron emission tomography (PET) tracer with a pseudo-irreversible binding mode. We demonstrate a novel protecting group strategy for 18F radiolabeling of carbamate precursors and show that the inhibitory potency as well as kinetic properties of our unlabeled reference compound were retained in comparison to the parent compound. In particular, the prolonged duration of enzyme inhibition of such a morpholinocarbamate motivated us to design a PET tracer, possibly enabling a precise mapping of BChE distribution.}, language = {en} } @article{HartrampfWeinzierlBucketal.2022, author = {Hartrampf, Philipp E. and Weinzierl, Franz-Xaver and Buck, Andreas K. and Rowe, Steven P. and Higuchi, Takahiro and Seitz, Anna Katharina and K{\"u}bler, Hubert and Schirbel, Andreas and Essler, Markus and Bundschuh, Ralph A. and Werner, Rudolf A.}, title = {Matched-pair analysis of [\(^{177}\)Lu]Lu-PSMA I\&T and [\(^{177}\)Lu]Lu-PSMA-617 in patients with metastatic castration-resistant prostate cancer}, series = {European Journal of Nuclear Medicine and Molecular Imaging}, volume = {49}, journal = {European Journal of Nuclear Medicine and Molecular Imaging}, number = {9}, doi = {10.1007/s00259-022-05744-6}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-324581}, pages = {3269-3276}, year = {2022}, abstract = {Background Labelled with lutetium-177, the urea-based small molecules PSMA I\&T and PSMA-617 are the two agents most frequently used for radioligand therapy (RLT) in patients with advanced metastatic castration-resistant and prostate-specific membrane antigen (PSMA) expressing prostate cancer (mCRPC). In this matched-pair analysis, we aimed to compare the toxicity and efficacy of both agents for PSMA-directed RLT. Materials and methods A total of 110 mCRPC patients from two centres were accrued, 55 individuals treated with [\(^{177}\)Lu]Lu-PSMA I\&T, and a matched cohort of 55 patients treated with [\(^{177}\)Lu]Lu-PSMA-617. Matching criteria included age at the first cycle, Gleason score, prostate-specific antigen (PSA) values, and previous taxane-based chemotherapy. Using common terminology criteria for adverse events (CTCAE v. 5.0), toxicity profiles were investigated (including bone marrow and renal toxicity). Overall survival (OS) between both groups was compared. Results Toxicity assessment revealed grade III anaemia in a single patient (1.8\%) for [\(^{177}\)Lu]Lu-PSMA I\&T and five (9.1\%) for [\(^{177}\)Lu]Lu-PSMA-617. In addition, one (1.9\%) grade III thrombopenia for [\(^{177}\)Lu]Lu-PSMA-617 was recorded. Apart from that, no other grade III/IV toxicities were present. A median OS of 12 months for patients treated with [\(^{177}\)Lu]Lu-PSMA I\&T did not differ significantly when compared to patients treated with [\(^{177}\)Lu]Lu-PSMA-617 (median OS, 13 months; P = 0.89). Conclusion In this matched-pair analysis of patients receiving one of the two agents most frequently applied for PSMA RLT, the rate of clinically relevant toxicities was low for both compounds. In addition, no relevant differences for OS were observed.}, language = {en} }