Radiolabelled Tracers Research Articles

322 Nutrient transport across gastrointestinal tissues using Ussing chambers

Abstract One of the principal roles of the gut is the absorption of nutrients to meet animal needs. While in vivo measures such as total tract digestibility indicate the totality of the nutrients that disappear, these methods provide no information on the digestion, site, flux, and mechanism of nutrient absorption. Nutrient absorption is a complex set of transport pathways including passive diffusion, facilitated transport, ion exchange, active transport, and secondary active transport that is driven by electrochemical gradients. To tease apart the complexities of nutrient transport at different sites along the gastrointestinal tract, Ussing chambers have been a useful tool. Two ex vivo chambers, filled with oxygenated physiological buffer, and separated by epithelial tissue allow for the detection of nutrient flux, transepithelial currents, and/or membrane permeability. Historically, detection of the nutrient of interest was achieved using radio-labelled or fluorescent tracers. Beyond detecting flux (uptake, efflux, net flux), Ussing chambers can also tease apart the complex network of transport pathways that govern nutrient absorption. Isolating specific transport pathways can be broad spectrum inhibitors, and alterations to the physiological buffers to target transport pathways of interest. Altering the electrical gradient using a voltage clamp for instance, can be used to neutralize, inhibit, or promote, the electrical gradient; such alterations can be especially useful for charged nutrients. Inhibitors, meanwhile, inhibit the activity of entire families of proteins, useful for when the role of specific protein transporters is of interest. Alterations to buffer composition, such as bicarbonate-free buffer solutions or the inclusion and exclusion of compounds with similar size and charge, can isolate transport solely dependent on that solute or provide knowledge on the solutes that may share a common transport mechanism. Together, these modulations allow for a powerful tool to study the presence or absence of nutrient transport and has been crucial in establishing absorption kinetics of ionic nutrients (e.g., Na+, Cl-), small organic nutrients (e.g., short chain fatty acids, glucose), and macromolecules (e.g., immunoglobulins). Done in conjunction with other techniques, Ussing chambers can offer strong insight to improve our understanding of nutrient absorption and epithelial physiology of the gut. This presentation will discuss the methods key to successful use of Ussing chambers, alongside with their limitations and ways to augment data generated by Ussing chambers.

Commentary: Tracing the fate of metabolic substrates during changes in whole-body energy expenditure in mice

For small mammals, such as mice, cannulation procedures can be quite challenging, limiting research associated with tracing isotopically labelled substrates at the whole-animal level. When cannulation in mice is possible, assessment of substrate use is further limited to when mice are either under anesthesia or are at rest, as there are no studies directly quantifying substrate use during exercise in mice. The use of isotopic tracer techniques has greatly advanced our knowledge in understanding how metabolic substrates (carbohydrates, amino acids, and fatty acids) contribute to whole-body metabolism. However, research regarding tissue-specific fuel use contributions to whole-body energy expenditure in mice at varying metabolic intensities (i.e., exercise) is lacking, despite the popularity of using mice in a variety of metabolic models. In this commentary, we briefly discuss the methodologies, advantages, and disadvantages of using radiolabelled, positron emission, and stable isotopes with a specific focus on fatty acids. We highlight recent mouse studies that have used creative experimental designs employing the use of isotopic tracer techniques and we briefly discuss how these methodologies can be further pursued to deepen our understanding of substrate use during exercise. Lastly, we show findings of a recent study we performed using a radiolabelled fatty acid tracer (14C-bromopalmitic acid) to determine fatty acid uptake in 16 muscles, two brown and two white adipose tissue depots during submaximal exercise in deer mice.

ABC Efflux Transporters and Solute Carriers in the Early Developing Brain of a Marsupial Monodelphis domestica (South American Gray Short-Tailed Opossum).

This study used a marsupial Monodelphis domestica, which is born very immature and most of its development is postnatal without placental protection. RNA-sequencing (RNA-Seq) was used to identify the expression of influx and efflux transporters (ATP-binding cassettes [ABCs] and solute carriers [SLCs]) and metabolizing enzymes in brains of newborn to juvenile Monodelphis. Results were compared to published data in the developing eutherian rat. To test the functionality of these transporters at similar ages, the entry of paracetamol (acetaminophen) into the brain and cerebrospinal fluid (CSF) was measured using liquid scintillation counting following a single administration of the drug along with its radiolabelled tracer [3H]. Drug permeability studies found that in Monodelphis, brain entry of paracetamol was already restricted at P5; it decreased further in the first week of life and then remained stable until the oldest age group tested (P110). Transcriptomic analysis of Monodelphis brain showed that expression of transporters and their metabolizing enzymes in early postnatal (P) pups (P0, P5, and P8) was relatively similar, but by P109, many more transcripts were identified. When transcriptomes of newborn Monodelphis brain and E19 rat brain and placenta were compared, several transporters present in the rat placenta were also found in the newborn Monodelphis brain. These were absent from E19 rat brain but were present in the adult rat brain. These data indicate that despite its extreme immaturity, the newborn Monodelphis brain may compensate for the lack of placental protection during early brain development by upregulating protective mechanisms, which in eutherian animals are instead present in the placenta.

Examination of the PET in vivo generator 134Ce as a theranostic match for 225Ac.

The radionuclide pair cerium-134/lanthanum-134 (134Ce/134La) was recently proposed as a suitable diagnostic counterpart for the therapeutic alpha-emitter actinium-225 (225Ac). The unique properties of 134Ce offer perspectives for developing innovative in vivo investigations that are not possible with 225Ac. In this work, 225Ac- and 134Ce-labelled tracers were directly compared using internalizing and slow-internalizing cancer models to evaluate their in vivo comparability, progeny meandering, and potential as a matched theranostic pair for clinical translation. Despite being an excellent chemical match, 134Ce/134La has limitations to the setting of quantitative positron emission tomography imaging. The precursor PSMA-617 and a macropa-based tetrazine-conjugate (mcp-PEG8-Tz) were radiolabelled with 225Ac or 134Ce and compared in vitro and in vivo using standard (radio)chemical methods. Employing biodistribution studies and positron emission tomography (PET) imaging in athymic nude mice, the radiolabelled PSMA-617 tracers were evaluated in a PC3/PIP (PC3 engineered to express a high level of prostate-specific membrane antigen) prostate cancer mouse model. The 225Ac and 134Ce-labelled mcp-PEG8-Tz were investigated in a BxPC-3 pancreatic tumour model harnessing the pretargeting strategy based on a trans-cyclooctene-modified 5B1 monoclonal antibody. In vitro and in vivo studies with both 225Ac and 134Ce-labelled tracers led to comparable results, confirming the matching pharmacokinetics of this theranostic pair. However, PET imaging of the 134Ce-labelled precursors indicated that quantification is highly dependent on tracer internalization due to the redistribution of 134Ce's PET-compatible daughter 134La. Consequently, radiotracers based on internalizing vectors like PSMA-617 are suited for this theranostic pair, while slow-internalizing 225Ac-labelled tracers are not quantitatively represented by 134Ce PET imaging. When employing slow-internalizing vectors, 134Ce might not be an ideal match for 225Ac due to the underestimation of tumour uptake caused by the in vivo redistribution of 134La. However, this same characteristic makes it possible to estimate the redistribution of 225Ac's progeny noninvasively. In future studies, this unique PET in vivo generator will further be harnessed to study tracer internalization, trafficking of receptors, and the progression of the tumour microenvironment.

Utility of F-15 diuretic MAG3 renography in assessment of paediatric hydronephrosis

Diuretic renography is crucial in evaluation of paediatric hydronephrosis. Furosemide is conventionally given 15-20min after radiolabelled tracer (F+15/F+20 protocol), however this is equivocal in around 15% of patients. Giving furosemide 15min prior to tracer (F-15 MAG3 protocol) has been suggested as an additional tool in the investigation of patients with suspected upper urinary tract obstruction. However, the role of this method in assessment and management of paediatric hydronephrosis is not widely reported. To investigate utility of F-15 renograms in children with hydronephrosis being assessed for Pelvi-Ureteric Junction Obstruction (PUJO). Retrospective review of patients <16 years old undergoing F-15 MAG3 renogram between 2018 and 2021 in our tertiary paediatric surgical centre. Data collected included patient demographics, mode of presentation, investigations, management and outcomes. Eighteen patients were included. Median age at F-15 renogram was 7.3 years. Eleven patients presented with antenatal hydronephrosis, 5 with symptoms in childhood and 2 with incidental hydronephrosis on trauma imaging. Fourteen patients were symptomatic. Ten had a prior non-obstructed F+20 renogram but persisting symptoms suggestive of PUJO. Seven had previous equivocal F+20 renograms. One symptomatic patient directly underwent an F-15 renogram. A conclusive result was obtained in 16/18 (89%); 11 patients had obstructed curves and 5 non-obstructed. Two asymptomatic patients' scans were inconclusive. All symptomatic patients had conclusive scans. Of 11 patients with an obstructed F-15, 9 have undergone pyeloplasty to date. All have had post-operative resolution in symptoms and static or improved post-operative ultrasound. One patient with an inconclusive scan underwent pyeloplasty due to persisting hydronephrosis and parent preference. Three patients with non-obstructed F-15 renograms have been discharged. One symptomatic patient with a non-obstructive F-15 had a ureteric stent inserted due to persistent flank pain; 1 continues under surveillance. It is known that conventional F+20 MAG3 renograms can give equivocal results. Published experience suggests that F-15 renograms are conclusive in the majority of patients. Routine primary use is, however, discouraged as they can 'over diagnose' obstruction and limit the study of tracer transit under physiological flow rates. This study indicates that the F-15 renogram is a useful adjunct in the assessment of patients with symptoms suggestive of PUJO who have previously had an equivocal or a non-obstructed F+20 renogram. F-15 renogram was conclusive in 89% of patients. We recommend using F-15 renograms to aid surgical decision-making in children with equivocal F+20 renograms, especially in the presence of symptoms.

Synthesis and initial evaluation of radioiodine-labelled deuterated tropane derivatives targeting dopamine transporter

The dopamine transporter (DAT) is closely related to a variety of neurological disorders including Parkinson’s disease (PD) and other neurodegenerative diseases. In vivo imaging of DAT with radio-labelled tracers has become a powerful technique in related disorders. The radioiodine-labelled tropane derivative [123I]FP-CIT ([123I]1a) is widely used in clinical single photon emission computed tomography (SPECT) imaging as a DAT imaging agent. To develop more metabolically stable DAT radioligands for accurate imaging, this work compared two novel deuterated tropane derivatives ([131I]1c-d) with non-deuterated tropane derivatives ([131I]1a-b). [131I]1a-d were obtained in high radiochemical purity (RCP) above 99 % with molar activities of 7.0–10.0 GBq/μmol. The [131I]1a and [131I]1c exhibited relatively higher affinity to DAT (Ki: 2.0–3.12 nM) than [131I]1b and [131I]1d. Biodistribution results showed that [131I]1c consistently exhibited a higher ratio of the target to non-target (striatum/cerebellum) than [131I]1a. Furthermore, metabolism studies indicated that the in vivo metabolic stability of [131I]1c was superior to that of [131I]1a. Ex vivo autoradiography showed that [131I]1c selectively localized on DAT-rich striatal regions and the specific signal could be blocked by DAT inhibitor. These results indicated that [131I]1c might be a potential probe for DAT SPECT imaging in the brain.

Chemistry and Pharmacology of Fluorinated Drugs Approved by the FDA (2016-2022).

Fluorine is characterized by high electronegativity and small atomic size, which provide this molecule with the unique property of augmenting the potency, selectivity, metabolic stability, and pharmacokinetics of drugs. Fluorine (F) substitution has been extensively explored in drug research as a means of improving biological activity and enhancing chemical or metabolic stability. Selective F substitution onto a therapeutic or diagnostic drug candidate can enhance several pharmacokinetic and physicochemical properties such as metabolic stability and membrane permeation. The increased binding ability of fluorinated drug target proteins has also been reported in some cases. An emerging line of research on F substitution has been addressed by using 18F as a radiolabel tracer atom in the extremely sensitive methodology of positron emission tomography (PET) imaging. This review aims to report on the fluorinated drugs approved by the US Food and Drug Administration (FDA) from 2016 to 2022. It cites selected examples from a variety of therapeutic and diagnostic drugs. FDA-approved drugs in this period have a variety of heterocyclic cores, including pyrrole, pyrazole, imidazole, triazole, pyridine, pyridone, pyridazine, pyrazine, pyrimidine, triazine, purine, indole, benzimidazole, isoquinoline, and quinoline appended with either F-18 or F-19. Some fluorinated oligonucleotides were also authorized by the FDA between 2019 and 2022.

Insight into Tumor Hypoxia: Radionuclide-based Biomarker as Diagnostic Tools.

The radiolabeled tracers have been extensively utilized to access various physiological and pathological conditions non-invasively, such as cancers, inflammation, and organ-specific imaging. These tracers demonstrate and study tumor hypoxia in several malignancies. Hypoxia is commonly seen in solid tumors.Tumor Hypoxia is a non-physiological condition of reduced oxygen concentration in the tumor. Hypoxia is associated with adverse outcomes such as treatment resistance and metastases in solid tumors. Tumor hypoxia may result in resistance to radiation therapy and chemotherapy, leading to a poor prognosis.It is one of the clinically paramount factors in treatment planning. Various chemical scaffolds are labeled with compatible radioisotopes for imaging hypoxia by Single-photon emission computed tomography (SPECT) and Positron emission tomography (PET). Radionuclides, such as [18F]Flourine, [99mTc]Technetium, [131I]Iodine, [124I]Iodine, and [64Cu]Copper are used for incorporation into different chemical scaffolds.Among them, [18F]Flourine and [64Cu] Copper tagged radiopharmaceuticals are most explored, such as [18F]FMISO, [18F]FAZA, [18F]FETNIM, and N4-methyl thiosemicarbazone [64Cu][Cu (ATSM)]. Some of the promising scaffolds for imaging hypoxia are [18F]EF1, [18F]EF5, [18F]EF3, and [18F]HX4. This review is focused on developing radiochemistry routes to synthesize different radiopharmaceuticals for imaging hypoxia in clinical and preclinical studies, as described in the literature. The chemist and radiochemist exerted enormous efforts to overcome these obstacles. They have successfully formulated multiple radiopharmaceuticals for hypoxia imaging. Radionuclide incorporation in high selectivity and efficiency (radiochemical yield, specific activity, purity, and radio-scalability) is a need for application perspective. Versatile chemistry, including nucleophilic and electrophilic substitutions, allows the direct or indirect introduction of radioisotopes into molecules of interest. This review will discuss the chemical routes for synthesizing and utilizing different precursors for radiolabeling withradionuclides.We will briefly summaries these radio-labeled tracers' application and biological significance.

Vascular calcification maladaptively participates in acute phosphate homeostasis.

Non-renal extravasation of phosphate from the circulation and transient accumulation into tissues and extracellular fluid is a regulated process of acute phosphate homeostasis that is not well understood. This process is especially relevant in the setting of chronic kidney disease (CKD), where exposure to increased phosphate is prolonged due to inefficient kidney excretion. Furthermore, CKD-associated mineral dysregulation induces pathological accumulation of phosphate causing vascular calcification (VC). Our objective was to determine whether the systemic response to acute phosphate challenges is altered by VC. After bolus phosphate administration, circulating and tissue deposition of this challenge was assessed in two rat models of VC using a radiolabelled phosphate tracer. In an adenine-induced model of CKD (N = 70), animals with VC had a blunted elevation of circulating 33PO4 following oral phosphate administration (P < 0.01), and the discordant deposition could be traced to the calcified arteries (11.4 [7.5-13.1] vs.43.0 [35.5-53.7] pmol/ng tissue, P < 0.001). In a non-CKD model of VC, calcification was induced with 0.5 ug/kg calcitriol and then withdrawn (N = 24). New phosphate uptake by the calcified vasculature correlated to the pre-existing burden of calcification (r = 38, P < 0.001) and was substantially attenuated in the absence of calcification stimulus (P < 0.01). Phosphate accrual was stimulated by the phosphate challenge and not present to the same degree during passive disposition of circulating phosphate. Further, the form of phosphate that deposited to the vasculature was predominately amorphous inorganic phosphate and not that which was bound in matured calciprotein particles. In the process of calcification, arteries acutely deposit substantial amorphous phosphate while blunting the elevation in the circulation, thereby altering the systemic disposition of phosphate and identifying VC as a participatory mineral homeostatic organ. This study demonstrates the negative vascular consequence of acute fluctuations in circulating phosphate, and supports the importance of phosphate bioavailability and diet management in CKD patients as a mediator of cardiovascular risk.

Visualising long distance sugar transport in fungi using infrared fluorescence scanning imaging

Mycelia of saprotrophic basidiomycetes can cover large areas in nature that are typified by their heterogeneous nutrient availability. This heterogeneity is overcome by long distance transport of nutrients within the hyphal network to sites where they are needed. It is therefore key to be able to study nutrient transport and its underlying mechanisms. An IRDye-conjugate was used for the first time for imaging transport in fungi. A method was set up for time-lapse, high spatial resolution infrared imaging of IRDye-labelled deoxyglucose (IRDye-DG) in Schizophyllum commune and Agaricus bisporus. Scanning imaging visualised the tracer in individual hyphae as well as deeper tissues in mushrooms (mm-cm depth). The advantage of using fluorescence scanning imaging of IRDye in contrast to radiolabelled tracers studies, is that a higher spatial resolution and higher sensitivity (244 fg/ml) can be obtained. Moreover, it has a large field of view (25 × 25 cm) compared to microscopy (µm-mm range), allowing relatively fast and detailed imaging of large dimension samples.

Cardiac functional imaging

During the last 20 years, cardiac imaging has drastically evolved. Positron emission tomography (PET), fast three-dimensional (3D) imaging with the latest generations of echocardiography & multi-detector computed tomography (CT), stress perfusion assessed by magnetic resonance imaging (MRI), blood flow analysis using four-dimensional (4D) flow MRI, all these techniques offer new trends for optimal noninvasive functional cardiac imaging. Dynamic functional imaging is obtained by acquiring images of the heart at different phases of the cardiac cycle, allowing assessment of cardiac motion, function, and perfusion. Between CT and Cardiac MRI (CMR), CMR has the best temporal resolution, which is suitable for functional imaging while cardiac CT provides higher spatial resolution with isotropic data that have an identical resolution in the three dimensions of the space. The latest generations of CT scanners enable whole heart assessment in one beat, offering also an acceptable temporal resolution with the possibility to display the images in a dynamic mode. Another rapidly growing technique using functional and molecular imaging for the assessment of biological and metabolic pathways is the PET using radio-labeled tracers. Meanwhile, the oldest cardiac imaging tool with doppler ultrasound technology has never stopped evolving. Echocardiography today performs 3D imaging, stress perfusion, and myocardial strain assessment, with high temporal resolution. It still is the first line and more accessible exam for the patient. These different modalities are complementary and may be even combined into PET-CT or PET-MRI. The ability to combine the functional/molecular data with anatomical images may implement a new dimension to our diagnostic tools.

Synthesis and biological evaluation of 18F-labelled dopamine D3 receptor selective ligands

The dopamine D3 receptor (D3R) is highly expressed in the limbic regions of the brain and closely related to a variety of neurological disorders including Parkinson's disease, schizophrenia and drug-seeking behavior. In vivo imaging of D3R with radio-labelled tracers and positron emission tomography (PET) has become a powerful technique in related disorders. In this study, we synthesized three novel aromatically 18F-labelled phenylpiperazine-like D3R selective radioactive ligands ([18F]5b, [18F]8b and [18F]11b) and developed a simple, rapid and efficient 18F-labelling method by condition optimization. Radiosynthesis of [18F]5b, [18F]8b and [18F]11b was achieved by 18F-fluorination from nitroarene precursors. Final radiochemical purities of [18F]5b, [18F]8b and [18F]11b solution were > 99% and remained good stability (> 98% for up to 6 h) in PBS and FBS. PET imaging and cellular binding studies revealed that [18F]8b had a higher D3R affinity than [18F]5b and [18F]11b. Autoradiography and biodistribution studies of the brain showed that [18F]8b had medium intensity specific accumulation in the striatum and cortex. Meanwhile, the low skeletal uptake of [18F]8b revealed a good in vivo stability with negligible defluorination. These results indicated that [18F]8b might be a potential 18F-labelled D3R PET imaging agent.

Abstract 10915: Unappreciated Mechanisms of Fatty Acid Uptake in the Kidney: Fatty Acids Are Taken Up from Both Basolateral and Apical Side

Introduction: The kidney combusts a large amount of fatty acid (FA) for body fluid homeostasis. Despite the high demand for FA, however, little is known about the mechanisms of FA uptake. We aimed to determine how FAs are taken up by tubular epithelial cells. Methods and Results: Immunohistochemistry showed that CD36, known as an important FA transporter in the heart, was also expressed in the basolateral side of proximal tubule epithelial cells (PTECs). The uptake of 125 I-BMIPP, radio-labeled FA tracer, was significantly reduced in the kidney in CD36 knockout mice 1 min after its injection compared with wild-type mice, while the significant difference disappeared 30 min after the injection. In vivo imaging with two-photon microscopy revealed that BODIPY-C 12 , fluorescence-labeled FA tracer, was accumulated in the basolateral side (blood side) of PTECs shortly after its injection, which was followed by accumulation in the apical side (primary urine side), suggesting bidirectional FA uptake by PTECs. A large amount of neutral lipid was accumulated in the kidney when serum FA concentration was increased by accelerated lipolysis by administration of a β3 adrenergic receptor agonist. Immunofluorescence with cell-specific antibodies revealed that the cells with the most abundant lipid accumulation were PTECs, followed by tubular epithelial cells of the distal nephron. In addition, neutral lipid accumulation was enhanced even in the distal nephron when PTECs were injured with administrations of diphtheria toxin (DT) in mice overexpressing DT-receptor in a PTEC-specific manner. Importantly, the PTEC-injured mice exhibited marked albuminuria, suggesting disturbance of protein reabsorption. Despite marked albuminuria, however, urinary FA was not detected at all, suggesting complete FA reabsorption independently of albumin reabsorption in the kidney. Conclusions: Our results revealed the unique and prominent capability of proximal and distal tubular epithelial cells to take up FA from both blood (CD36-dependent) and primary urine (CD36-independent) and to store them as neutral lipids. We further suggest that the kidney acts not only as FA consuming tissue but also as FA keeping tissue to completely reabsorb FA from primary urine for unwasted energy use.

Congress of neurological surgeons systematic review and evidence-based guidelines update on the role of emerging developments in the management of newly diagnosed glioblastoma

These recommendations apply to adult patients with newly diagnosed or suspected glioblastoma. Question What imaging modalities are in development that may be able to provide improvements in diagnosis, and therapeutic guidance for individuals with newly diagnosed glioblastoma? Level III: It is suggested that techniques utilizing magnetic resonance imaging for diffusion weighted imaging, and to measure cerebral blood and magnetic spectroscopic resonance imaging of N-acetyl aspartate, choline and the choline to N-acetyl aspartate index to assist in diagnosis and treatment planning in patients with newly diagnosed or suspected glioblastoma. Question What new surgical techniques can be used to provide improved tumor definition and resectability to yield better tumor control and prognosis for individuals with newly diagnosed glioblastoma? Level II: The use of 5-aminolevulinic acid is recommended to improve extent of tumor resection in patients with newly diagnosed glioblastoma. Level II: The use of 5-aminolevulinic acid is recommended to improve median survival and 2 year survival in newly diagnosed glioblastoma patients with clinical characteristics suggesting poor prognosis. Level III: It is suggested that, when available, patients be enrolled in properly designed clinical trials assessing the value of diffusion tensor imaging in improving the safety of patients with newly diagnosed glioblastoma undergoing surgery. Question What new pathology techniques and measurement of biomarkers in tumor tissue can be used to provide improved diagnostic ability, and determination of therapeutic responsiveness and prognosis for patients with newly diagnosed glioblastomas? Level II: Assessment of tumor MGMT promoter methylation status is recommended as a significant predictor of a longer progression free survival and overall survival in patients with newly diagnosed with glioblastoma. Level II: Measurement of tumor expression of neuron-glia-2, neurofilament protein, glutamine synthetase and phosphorylated STAT3 is recommended as a predictor of overall survival in patients with newly diagnosed with glioblastoma. Level III: Assessment of tumor IDH1 mutation status is suggested as a predictor of longer progression free survival and overall survival in patients with newly diagnosed with glioblastoma. Level III: Evaluation of tumor expression of Phosphorylated Mitogen-Activated Protein Kinase protein, EGFR protein, and Insulin-like Growth Factor-Binding Protein-3 is suggested as a predictor of overall survival in patients with newly diagnosed with glioblastoma. Question What radiation therapy techniques are in development that may be used to provide improved tumor control and prognosis for individuals with newly diagnosed glioblastomas? Level III: It is suggested that patients with newly diagnosed glioblastoma undergo pretreatment radio-labeled amino acid tracer positron emission tomography to assess areas at risk for tumor recurrence to assist in radiation treatment planning. Level III: It is suggested that, when available, patients be with newly diagnosed glioblastomas be enrolled in properly designed clinical trials of radiation dose escalation, altered fractionation, or new radiation delivery techniques. Question What emerging chemotherapeutic agents or techniques are available to provide better tumor control and prognosis for patients with newly diagnosed glioblastomas? Level III: As no emerging chemotherapeutic agents or techniques were identified in this review that improved tumor control and prognosis it is suggested that, when available, patients with newly diagnosed glioblastomas be enrolled in properly designed clinical trials of chemotherapy. Question What new targeted therapy agents are available to provide better tumor control and prognosis for individuals with newly diagnosed glioblastomas? Level III: As no new molecular and targeted therapies have clearly provided better tumor control and prognosis it is suggested that, when available, patients with newly diagnosed glioblastomas be enrolled in properly designed clinical trials of molecular and targeted therapies IMMUNOTHERAPY: Question What emerging immunotherapeutic agents or techniques are available to provide better tumor control and prognosis for patients with newly diagnosed glioblastomas? Level III: As no immunotherapeutic agents have clearly provided better tumor control and prognosis it is suggested that, when available, patients with newly diagnosed glioblastomas be enrolled in properly designed clinical trials of immunologically-based therapies. Question What novel therapies or techniques are in development to provide better tumor control and prognosis for individuals with newly diagnosed glioblastomas? Level II: The use of tumor-treating fields is recommended for patients with newly diagnosed glioblastoma who have undergone surgical debulking and completed concurrent chemoradiation without progression of disease at the time of tumor-treating field therapy initiation. Level II: It is suggested that, when available, enrollment in properly designed studies of vector containing herpes simplex thymidine kinase gene and prodrug therapies be considered in patients with newly diagnosed glioblastoma.

Evaluation of covalent binding of flutamide and its risk assessment using 19F-NMR

The formation of reactive metabolites (RMs) is a problem in drug development that sometimes results in severe hepatotoxicity. As detecting RMs themselves is difficult, a covalent binding assay using expensive radiolabelled tracers is usually performed for candidate selection. This study aimed to provide a practical approach toward the risk assessment of hepatotoxicity induced by covalent binding before candidate selection. We focused on flutamide because it contains a trifluoromethyl group that shows a strong singlet peak by 19F nuclear magnetic resonance (NMR) spectrometry. The covalent binding of flutamide was evaluated using quantitative NMR and its risk for hepatotoxicity was assessed by estimating the RM burden, an index that reflects the body burden associated with RM exposure by determining the extent of covalent binding, clinical dose and in vivo clearance. The extent of covalent binding and RM burden was 296 pmol/mg/h and 37.9 mg/day, respectively. Flutamide was categorised as high risk with an RM burden >10 mg/day consistent with its clinical hepatotoxicity. These results indicate that a combination of covalent binding assay using 19F-NMR and RM burden is useful for the risk assessment of RMs without using radiolabelled compounds.

Enhanced cometabolism of benzo(a)anthracene by the lignin monomer vanillate is related to structural and functional responses of the soil microbiome

Lignin is a natural polymer composed of phenolic units. The structural similarity between lignin monomers and recalcitrant aromatic pollutants raises the possibility of their cometabolism by soil microorganisms. Here, we explored the links between polycyclic aromatic hydrocarbon (PAH) degradation and microbiome responses in soil microcosms amended with lignin or one of its phenolic units, vanillate, by coupled amplicon and metagenomic shotgun sequencing. The transformation of the four-ring model PAH benzo(a)anthracene (BaA) was monitored by using a radiolabelled tracer. The results demonstrated that vanillate significantly promoted 14CO2 production during incubation, suggesting activation of BaA biodegradation in the soil microcosms. Lignin changed the fate of BaA mainly by increasing its adsorption to soil organic matter. In contrast to the control microcosms, the mineralization and formation of nonextractable residue (NER) from BaA in the presence of vanillate were sensitive to the fungicide cycloheximide. Lignin and vanillate consistently enriched bacterial methyl utilization and aromatic ring cleavage genes at the two sampling times, which, however, did not result in BaA mineralization. The distinct responses of the fungal community to vanillate as well as the coupled cycloheximide-induced inhibition of BaA mineralization and 18S rRNA gene abundance suggest an essential contribution of fungi to BaA biodegradation in the vanillate-amended microcosms. Overall, these findings reveal a cometabolic mechanism between vanillate and PAHs, which contributed to the detoxification of BaA in the soil. This study also provides a scientific basis for the bioremediation of PAH-contaminated soil by priming the soil microbiome with phenolic monomers of lignin.

Rapid identification of a novel phosphodiesterase 7B tracer for receptor occupancy studies using LC─MS/MS

Phosphodiesterase 7B (PDE7B) inhibition has been considered as a therapeutic target for the treatment of several neurological disorders. Currently, there are no radio-labeled tracers available to determine receptor occupancy (RO) of this target. Developing such a tracer could greatly facilitate the identification of viable PDE7B inhibitors. In the current study, a liquid chromatography tandem mass spectrometry (LC─MS/MS) method was utilized to evaluate the brain distribution of unlabeled tracer candidates following intravenous micro-dosing. This novel approach resulted in an accelerated identification of a potential novel RO tracer for PDE7B. The identified molecule, Compound 30, showed reasonable target-tissue specificity (striatum/cerebellum ratio of 2.2) and suitable uptake (0.25% of the injected dose/g brain tissue) as demonstrated in rats dosed with the unlabeled compound. Compound 30 was subsequently labeled with tritium (3H). In vitro characterization of 3H-Compound 30 demonstrated that this compound possessed a high target affinity with a subnanomolar Kd (0.8 nM) and a Bmax of 58 fmol/mg of protein using rat brain homogenate. Intravenous microdosing of 3H-Compound 30 showed preferential binding in the rat striatum, consistent with the mRNA distribution of PDE7B. In vitro displacement study with other structurally distinct PDE7B target-specific inhibitors using rat brain homogenate indicated that 3H-Compound 30 is an ideal tracer for Ki analysis. This is the first report of a preclinical tracer for PDE7B. With further characterization, Compound 30 may ultimately show the appropriate properties required to be further developed as a PDE7B PET ligand for clinical studies.

P113 Imaging neoangiogenesis in rheumatoid arthritis (INIRA): whole-body synovial uptake of a 99mTc-labelled RGD peptide is highly correlated with power Doppler ultrasound

Abstract Background Power Doppler ultrasound (PDUS) is superior to clinical examination in detecting synovitis in patients with rheumatoid arthritis (RA). Although dynamic and cheap it is impractical to scan large numbers of joints in routine clinical settings. MRI, whilst sensitive for synovitis, is expensive and routine use is limited to targeted joints. Bone scintigraphy produces whole body images but due to lower specificity is not routinely used. 99mTc-maraciclatide (Serac Healthcare) is a radio-labelled tracer which binds with high affinity to integrin αvβ3 (αvβ3), a cell-adhesion molecule up-regulated on neoangiogenic blood vessels. It therefore has the potential to image synovial inflammation at the whole-body level. We previously showed in a pilot study that uptake was seen in the inflamed joints of 5 RA patients and that this correlated with PDUS. This study explores correlation with PDUS in a larger group of patients with varied disease activities. Methods 50 patients with RA, fulfilling ACR 2010 classification criteria, were recruited. Patients underwent an ultrasound scan of 40 joints with grey scale (GS) and PD quantification. Each joint was scored on a scale of 0-3 for GS and PD with a total score calculated for each patient. Within 3 hours of the ultrasound, patients were injected with 740 MBq of 99mTc-maraciclatide. Using a gamma camera, whole body planar views and dedicated hand and foot views were taken 2 hours after injection. Acquisition time was 20 minutes for whole body, and 20 minutes for hand and foot views. 99mTc-maraciclatide images were scored as positive or negative uptake for each joint (binary score). A quantitative score was also calculated for each joint where there was uptake with this corrected for background muscle uptake. Total binary and quantitative scores per patient were calculated. Ultrasound and 99mTc-maraciclatide scores were tested for correlation with Pearson’s correlation coefficient (r) and the coefficient of determination (r2). Results Strong correlation was seen when total PDUS was compared to binary scores (r = 0.92, r2=0.85) and quantitative scores (r = 0.85, r2=0.72). p was &amp;lt;0.0005 for all results. 99mTc-maraciclatide uptake was also seen in inflamed tendons/tendon sheaths. The imaging procedure was well-tolerated. Conclusion 99mTc-maraciclatide uptake was highly correlated with PDUS highlighting its potential as an alternative imaging modality. 99mTc-based planar imaging has the unique capacity to image the whole body and hence the total synovial inflammatory load in a quick acquisition. The imaging equipment to perform these scans is already widely available in radiology departments. Interpretation of scans is also much simpler compared to US/MRI. It could therefore have a role in key decision-making points in pathways for diagnosis, treatment failure, and remission prior to dose tapering. Disclosures L. Attipoe None. T. Garrood Grants/research support; Serac Healthcare. M. Opena None. C. Blanco-Gil None. S. Subesinghe None. S. Norton None. M. Rosser Other; Serac Healthcare Ltd. G. Cook None. A. Cope Grants/research support; AP received funding for research from BMS.

The Therapeutic and Diagnostic Value of Fluorine

Fluorine has a useful positron transmitting isotope and it enjoys broad application in the medical field. It is utilized in fluorinated agents,therapeutic sciences and steroid field. Fluorine incorporation viafluoroalkylation is a useful approach in the development of new functional materials and in drug design. Fluorine also plays its role as an anticancer agent and is a successful chemotherapeutic agent for certain sorts of malignant growth. 5-fluorouracil plays a vital role in the treatment of cancer. 18 Facts as a radio label tracer atom in PET imaging. 19 F has the second most sensitive and stable NMR-active nucleus.

Diagnostic Performance and Prognostic Value of PET/CT with Different Tracers for Brain Tumors: A Systematic Review of Published Meta-Analyses.

Background: Several meta-analyses reporting data on the diagnostic performance or prognostic value of positron emission tomography (PET) with different tracers in detecting brain tumors have been published so far. This review article was written to summarize the evidence-based data in these settings. Methods: We have performed a comprehensive literature search of meta-analyses published in the Cochrane library and PubMed/Medline databases (from inception through July 2019) about the diagnostic performance or prognostic value of PET with different tracers in patients with brain tumors. Results: We have summarized the results of 24 retrieved meta-analyses on the use of PET or PET/computed tomography (CT) with different tracers in brain tumors. The tracers included were: fluorine-18 fluorodeoxyglucose (18F-FDG), carbon-11 methionine (11C-methionine), fluorine-18 fluoroethyltyrosine (18F-FET), fluorine-18 dihydroxyphenylalanine (18F-FDOPA), fluorine-18 fluorothymidine (18F-FLT), and carbon-11 choline (11C-choline). Evidence-based data demonstrated good diagnostic performance of PET with different tracers in detecting brain tumors, in particular, radiolabelled amino acid tracers showed the highest diagnostic performance values. All the PET tracers evaluated had significant prognostic value in patients with glioma. Conclusions: Evidence-based data showed a good diagnostic performance for some PET tracers in specific indications and significant prognostic value in brain tumors.