Automated radiosynthesis and preclinical imaging of a novel [18F]fluorolidocaine analogue via sequential C-H radiolabelling.

The most prominent myocardial voltage-gated sodium channel, NaV1.5, is a major drug target for treating cardiovascular disease. However, treatment determination and therapeutic development are complicated partly by an inadequate understanding of how the density of SCN5A, the gene that encodes NaV1.5, relates to treatment response and disease prognosis. To address these challenges, imaging agents derived from NaV1.5 blocking therapeutics have been employed in positron emission tomography (PET) imaging to infer how SCN5A expression relates to human disease in vivo. Herein, we describe the preparation of a novel fluorine-18 labelled analogue of lidocaine, a known NaV1.5 inhibitor, and compare this agent to a previously described analogue. Evidence from rodent and non-human primate PET imaging experiments suggests that the imaging utility of these agents may be limited by rapid metabolism and clearance.

3AcFNP-59 for Positron Emission Tomography Imaging of Cholesterol Trafficking and Utilization.

Cholesteryl ester analogues of [18F]FNP-59 have the ability to provide information on cholesterol trafficking and utilization at earlier time points than those of [18F]FNP-59 or [131I]NP-59. It is well-known that free cholesterol and cholesteryl esters have differing distribution profiles and that they can be interconverted enzymatically. Substitution of the ester influences the rate of cholesterol ester hydrolysis and the subsequent mixing of cholesterol esters with the lipid pool in the body. This can be utilized by preparing esters that are more readily taken up by lipoprotein, are quickly hydrolyzed and mixed with the endogenous lipid pool and delivered to tissues of interest more quickly than free cholesterol analogues that require esterification for lipoprotein association. The acetyl ester of FNP-59 demonstrated the preferred uptake properties and response to adrenal cortical manipulation, indicating its ability to image hormone production. Finally, dosimetry studies were conducted in preparation for the clinical translation of [18F]3AcFNP-59.

Automated Radiosynthesis of [18F]FluoFAPI and Its Dosimetry and Single Acute Dose Toxicological Evaluation.

BACKGROUND: Cancer-associated fibroblasts have become a new target for therapy. Fibroblasts present within malignancies express the fibroblast activation protein (FAP). Inhibitors to FAP (FAPI) are small molecules recently developed as a theranostic agents for imaging and radiotherapy. All currently used FAPI rely on a linker-chelator complex attached to the 'inhibitor'. We describe a new automated method of the direct attachment of the radioisotope to the inhibitor, resulting in a >50% MW reduction with the hope of an improved tumor-to-background ratio and tumor uptake. METHODS: [18F]FluroFAPI was developed from a Sn precursor. This allowed for subsequent automated radioflourination. We obtained the biodistribution of [18F]FluroFAPI in rats, performed estimated human radiation dosimetry, and performed a 100× expected single dose toxicology analysis for eventual first-in-human experiments. RESULTS: The synthesis of the Sn precursor for FluorFAPI and the automated synthesis of [18F]FluroFAPI was demonstrated. [18F]FluroFAPI had favorable estimated human radiation dosimetry, and demonstrated no adverse effects when injected at a dose of 100× that planned for [18F]FluroFAPI. CONCLUSIONS: With the successful development of an automated synthesis of [18F]FluroFAPI, first-in-human testing can be planned with the hope of an improved tumor-to-background performance compared to other FAPI agents.

Development of High-Throughput Experimentation Approaches for Rapid Radiochemical Exploration.

Positron emission tomography is a widely used imaging platform for studying physiological processes. Despite the proliferation of modern synthetic methodologies for radiolabeling, the optimization of these reactions still primarily relies on inefficient one-factor-at-a-time approaches. High-throughput experimentation (HTE) has proven to be a powerful approach for optimizing reactions in many areas of chemical synthesis. However, to date, HTE has rarely been applied to radiochemistry. This is largely because of the short lifetime of common radioisotopes, which presents major challenges for efficient parallel reaction setup and analysis using standard equipment and workflows. Herein, we demonstrate an effective HTE workflow and apply it to the optimization of copper-mediated radiofluorination of pharmaceutically relevant boronate ester substrates. The workflow utilizes commercial equipment and allows for rapid analysis of reactions for optimizing reactions, exploring chemical space using pharmaceutically relevant aryl boronates for radiofluorinations, and constructing large radiochemistry data sets.

Inoculation of black turtle beans (Phaseolus vulgaris) with mycorrhizal fungi increases the nutritional quality of seeds.

The use of arbuscular mycorrhizal fungi (AMF) as biofertilizers has proven successful in boosting the yield and nutritional quality of a variety of crops. AMF associate with plant roots and exchange soil nutrients for photosynthetically derived C in the form of sugars and lipids. Past research has shown that not all AMF species are equal in their benefit to nutrient uptake and crop health, and that the most beneficial AMF species appear to vary by host species. Although an important human food staple, especially in developing regions where nutrient deficiency is a prevalent threat to public health, little work has been done to test the effectiveness of AMF in enhancing the nutritional quality of common bean (Phaseolus vulgaris L.). Therefore, our objective was to determine the most beneficial AMF species for inoculation of this important crop. We inoculated black beans (Phaseolus vulgaris black turtle beans) with eight individual AMF species and one mixed species inoculum in an outdoor pot trial over 3 months and assessed the extent to which they altered yield, mineral nutrient and anthocyanin concentration of seeds and leaf tissues. Despite seeing no yield effects from inoculation, we found that across treatments percent root length colonized by AMF was positively correlated with plant tissue P, Cu, and Zn concentration. Underlying these broad benefits, seeds from plants inoculated with three AMF species, Claroideoglomus claroideum (+15%), Funneliformis mosseae (+13%), and Gigaspora rosea (+11%) had higher P concentration than non-mycorrhizal plants. C. claroideum also increased seed potassium (K) and copper (Cu), as well as leaf aluminum (Al) concentration making it a promising candidate to further test the benefit of individual AMF species on black bean growth in field trials.

Zinc-Mediated Radiosynthesis of Unprotected Fluorine-18 Labelled α-Tertiary Amides.

This report describes the development of a Zn(OTf)2 -mediated method for converting α-tertiary haloamides to the corresponding fluorine-18 labelled α-tertiary fluoroamides with no-carrier-added [18 F]tetramethylammonium fluoride. 1,5,7-Triazabicyclo[4.4.0]dec-5-ene is an essential additive for achieving high radiochemical conversion. Under the optimised conditions, radiofluorination proceeds at sterically hindered tertiary sites in high radiochemical conversions, yields, and purities. This method has been successfully automated and applied to access >200 mCi (>7.4 GBq) of several model radiofluorides. Mechanistic studies led to the development of a new, nucleophilic C-H radiofluorination process using N-sulphonyloxyamide substrates.

Automated production of [11C]butyrate for keto body PET imaging.

The report describes an updated, fully automated method for the production of [11C]butyrate, validated for use in clinical studies. A commercially available GE Tracerlab FXM synthesis module was reconfigured to allow for air-free introduction of n-propyl magnesium chloride and to incorporate Sep-Pak cartridges to simplify and shorten the purification process, as compared to purifying the product using traditional HPLC. The method takes 20 min from end-of-bombardment and reliably produces injectable doses of [11C]butyrate (8029 ± 1628 MBq (217 ± 44 mCi), 14 % radiochemical yield based on [11C]CO2, non-decay corrected) in high radiochemical purity (>97 %), n = 3. With radiotracer in hand, PET scans of rats confirmed uptake of the radiopharmaceutical in the brain. Rat biodistribution data was obtained and used in conjunction with OLINDA software to determine an estimated human total body effective dose of 3.20 × 10-3 mSv/MBq (1.19 × 10-2 rem/mCi), along with preliminary rodent PET imaging that confirmed brain uptake. Lastly, our first human [11C]butyrate PET studies using a dynamic bolus injection technique (n = 5), with a graphical Logan analysis using a white matter reference region, confirmed good radiotracer uptake in the brain and with relatively more prominent uptake in the cerebellar hemispheres, vermis, cingulum cortex and the thalami.

A multisite evaluation of antifungal use in critical care: implications for antifungal stewardship.

Background: ICUs are settings of high antifungal consumption. There are few data on prescribing practices in ICUs to guide antifungal stewardship implementation in this setting. Methods: An antifungal therapy (AFT) service evaluation (15 May-19 November 2019) across ICUs at three London hospitals, evaluating consumption, prescribing rationale, post-prescription review, de-escalation and final invasive fungal infection (IFI) diagnostic classification. Results: Overall, 6.4% of ICU admissions (305/4781) received AFT, accounting for 11.41 days of therapy/100 occupied bed days (DOT/100 OBD). The dominant prescribing mode was empirical (41% of consumption), followed by targeted (22%), prophylaxis (18%), pre-emptive (12%) and non-invasive (7%). Echinocandins were the most commonly prescribed drug class (4.59 DOT/100 OBD). In total, 217 patients received AFT for suspected or confirmed IFI; 12%, 10% and 23% were classified as possible, probable or proven IFI, respectively. Hence, in 55%, IFI was unlikely. Proven IFI (n = 50) was mostly invasive candidiasis (92%), of which 48% had been initiated on AFT empirically before yeast identification. Where on-site (1 → 3)-ß-d-glucan (BDG) testing was available (1 day turnaround), in those with suspected but unproven invasive candidiasis, median (IQR) AFT duration was 10 (7-15) days with a positive BDG (≥80 pg/mL) versus 8 (5-9) days with a negative BDG (<80 pg/mL). Post-prescription review occurred in 79% of prescribing episodes (median time to review 1 [0-3] day). Where suspected IFI was not confirmed, 38% episodes were stopped and 4% de-escalated within 5 days. Conclusions: Achieving a better balance between promptly treating IFI patients and avoiding inappropriate antifungal prescribing in the ICU requires timely post-prescription review by specialist multidisciplinary teams and improved, evidence-based-risk prescribing strategies incorporating rapid diagnostics to guide AFT start and stop decisions.

Copper-Mediated Radiocyanation of Unprotected Amino Acids and Peptides.

This report describes a copper-mediated radiocyanation of aryl halides that is applicable to complex molecules. This transformation tolerates an exceptionally wide range of functional groups, including unprotected amino acids. As such, it enables the site-specific introduction of [11C]CN into peptides at an iodophenylalanine residue. The use of a diamine-ligated copper(I) mediator is crucial for achieving high radiochemical yield under relatively mild conditions, thus limiting racemization and competing side reactions of other amino acid side chains. The reaction has been scaled and automated to deliver radiolabeled peptides, including analogues of adrenocorticotropic hormone 1-27 (ACTH) and nociceptin (NOP). For instance, this Cu-mediated radiocyanation was leveraged to prepare >40 mCi of [11C]cyano-NOP to evaluate biodistribution in a primate using positron emission tomography. This investigation provides preliminary evidence that nociceptin crosses the blood-brain barrier and shows uptake across all brain regions (SUV > 1 at 60 min post injection), consistent with the known distribution of NOP receptors in the rhesus brain.

Development of Fluorinated NP-59: A Revival of Cholesterol Use Imaging with PET.

Imaging of cholesterol use is possible with the 131I scintiscanning/SPECT agent NP-59. This agent provided a noninvasive measure of adrenal function and steroid synthesis. However, iodine isotopes resulted in poor resolution, manufacturing challenges, and high radiation dosimetry to patients that have limited their use and clinical impact. A 18F analog would address these shortcomings while retaining the ability to image cholesterol use. The goal of this study was to prepare and evaluate a 18F analog of NP-59 to serve as a PET imaging agent for functional imaging of the adrenal glands based on cholesterol use. Previous attempts to prepare such an analog of NP-59 have proven elusive. Preclinical and clinical evaluation could be performed once the new fluorine analog of NP-59 production was established. Methods: The recent development of a new reagent for fluorination along with an improved route to the NP-59 precursor allowed for the preparation of a fluorine analog of NP-59, FNP-59. The radiochemistry for the 18F-radiolabeled 18F-FNP-59 is described, and rodent radiation dosimetry studies and in vivo imaging in New Zealand rabbits was performed. After in vivo toxicity studies, an investigational new drug approval was obtained, and the first-in-humans images with dosimetry using the agent were acquired. Results: In vivo toxicity studies demonstrated that FNP-59 is safe for use at the intended dose. Biodistribution studies with 18F-FNP-59 demonstrated a pharmacokinetic profile similar to that of NP-59 but with decreased radiation exposure. In vivo animal images demonstrated expected uptake in tissues that use cholesterol: gallbladder, liver, and adrenal glands. In this first-in-humans study, subjects had no adverse events and images demonstrated accumulation in target tissues (liver and adrenal glands). Manipulation of uptake was also demonstrated with patients who received cosyntropin, resulting in improved uptake. Conclusion: 18F-FNP-59 provided higher resolution images, with lower radiation dose to the subjects. It has the potential to provide a noninvasive test for patients with adrenocortical diseases.

Multiplex qPCR assays to distinguish individual species of arbuscular mycorrhizal fungi from roots and soil.

Currently, root colonization measurements of arbuscular mycorrhizal fungi (AMF) require staining and microscopy, and species-level identification of the fungi by such observations is not possible. Here, we present novel multiplex real-time PCR assays targeting the glomalin genes of 11 different species of AMF commonly found in temperate agricultural soils, which independently detect and measure the abundance of these fungi using DNA extracts from soil and or root tissue. The availability of these tools will not only increase throughput in determining levels of root colonization but can provide species-specific levels of root colonization from a single sample. This will help to establish which AMF species, or combinations of different species, provide the most benefits to crops, and will aid in the development of AMF for use as biofertilizers.

Synthesis and Evaluation of a Fluorine-18 Radioligand for Imaging Huntingtin Aggregates by Positron Emission Tomographic Imaging.

Mutations in the huntingtin gene (HTT) triggers aggregation of huntingtin protein (mHTT), which is the hallmark pathology of neurodegenerative Huntington's disease (HD). Development of a high affinity 18F radiotracer would enable the study of Huntington's disease pathology using a non-invasive imaging modality, positron emission tomography (PET) imaging. Herein, we report the first synthesis of fluorine-18 imaging agent, 6-(5-((5-(2,2-difluoro-2-(fluoro-18F)ethoxy)pyridin-2-yl)methoxy)benzo[d]oxazol-2-yl)-2-methylpyridazin-3(2H)-one ([18F]1), a radioligand for HD and its preclinical evaluation in vitro (autoradiography of post-mortem HD brains) and in vivo (rodent and non-human primate brain PET). [18F]1 was synthesized in a 4.1% RCY (decay corrected) and in an average molar activity of 16.5 ± 12.5 GBq/µmol (445 ± 339 Ci/mmol). [18F]1 penetrated the blood-brain barrier of both rodents and primates, and specific saturable binding in post-mortem brain slices was observed that correlated to mHTT aggregates identified by immunohistochemistry.

NHC-Copper Mediated Ligand-Directed Radiofluorination of Aryl Halides.

[18F]-labeled aryl fluorides are widely used as radiotracers for positron emission tomography (PET) imaging. Aryl halides (ArX) are particularly attractive precursors to these radiotracers, as they are readily available, inexpensive, and stable. However, to date, the direct preparation of [18F]-aryl fluorides from aryl halides remains limited to SNAr reactions between highly activated ArX substrates and K18F. This report describes an aryl halide radiofluorination reaction in which the C(sp2)-18F bond is formed via a copper-mediated pathway. Copper N-heterocyclic carbene complexes serve as mediators for this transformation, using aryl halide substrates with directing groups at the ortho position. This reaction is applied to the radiofluorination of electronically diverse aryl halide derivatives, including the bioactive molecules vismodegib and PH089.

Copper-Mediated Late-stage Radiofluorination: Five Years of Impact on Pre-clinical and Clinical PET Imaging.

PURPOSE: Copper-mediated radiofluorination (CMRF) is emerging as the method of choice for the formation of aromatic C-18F bonds. This minireview examines proof-of-concept, pre-clinical, and in-human imaging studies of new and established imaging agents containing aromatic C-18F bonds synthesized with CMRF. An exhaustive discussion of CMRF methods is not provided, although key developments that have enabled or improved upon the syntheses of fluorine-18 imaging agents are discussed. METHODS: A comprehensive literature search from April 2014 onwards of the Web of Science and PubMed library databases was performed to find reports that utilize CMRF for the synthesis of fluorine-18 radiopharmaceuticals, and these represent the primary body of research discussed in this minireview. Select conference proceedings, previous reports describing alternative methods for the synthesis of imaging agents, and preceding fluorine-19 methodologies have also been included for discussion. CONCLUSIONS: CMRF has significantly expanded the chemical space that is accessible to fluorine-18 radiolabeling with production methods that can meet the regulatory requirements for use in Nuclear Medicine. Furthermore, it has enabled novel and improved syntheses of radiopharmaceuticals and facilitated subsequent PET imaging studies. The rapid adoption of CMRF will undoubtedly continue to simplify the production of imaging agents and inspire the development of new radiofluorination methodologies.

Ring opening of epoxides with [18F]FeF species to produce [18F]fluorohydrin PET imaging agents.

A simple technique for the preparation of [18F]HF has been developed and applied to the generation of an [18F]FeF species for opening sterically hindered epoxides. This method has been successfully employed to prepare four drug-like molecules, including 5-[18F]fluoro-6-hydroxy-cholesterol, a potential adrenal/endocrine PET imaging agent. This easily automated one-pot procedure produces sterically hindered fluorohydrin PET imaging agents in good yields and high molar activities.

Accuracy and stability of deep inspiration breath hold in gated breast radiotherapy - A comparison of two tracking and guidance systems.

PURPOSE: To characterize reproducibility of patient breath-hold positioning and compare tracking system performance for Deep Inspiration Breath Hold (DIBH) gated left breast radiotherapy. METHODS: 29 consecutive left breast DIBH patients (655 fractions) were treated under the guidance of Calypso surface beacons with audio-feedback and 35 consecutive patients (631 fractions) were treated using C-RAD Catalyst HD surface imaging with audiovisual feedback. The Calypso system tracks a centroid determined by two radio-frequency transponders, with a manually enforced institutional tolerance, while the surface image based CatalystHD system utilizes real-time biometric feedback to track a pre-selected point with an institutional tolerance enforced by the Elekta Response gating interface. DIBH motion data from Calypso was extracted to obtain the displacement of breath hold marker in ant/post direction from a set-zero reference point. Ant/post point displacement data from CatalystHD was interpreted by computing the difference between raw tracking points and the center of individual gating windows. Mean overall errors were compared using Welsh's unequal variance t-test. Wilcoxon rank sum test were used for statistical analysis with P < 0.05 considered significant. RESULTS: Mean overall error for Calypso and CatalystHD were 0.33 ±â€¯1.17 mm and 0.22 ±â€¯0.43 mm, respectively, with t-test comparison P-value < 0.034. Absolute errors for Calypso and CatalystHD were 0.95 ±â€¯0.75 mm and 0.38 ±â€¯0.30 mm, respectively, with Wilcoxon rank sum test P-value <2×10-16. Average standard deviation per fraction was found to be 0.74 ±â€¯0.44 mm for Calypso patients versus 0.54 ±â€¯0.22 mm for CatalystHD. CONCLUSION: Reduced error distribution widths in overall positioning, deviation of position, and per fraction deviation suggest that the use of functionalities available in CatalystHD such as audiovisual biofeedback and patient surface matching improves accuracy and stability during DIBH gated left breast radiotherapy.

Association of Anaesthetists: anaesthesia and peri-operative care for Jehovah's Witnesses and patients who refuse blood.

There are approximately 8.5 million Jehovah's Witnesses and around 150,000 live in Great Britain and Ireland. Based on their beliefs and core values, Jehovah's Witnesses refuse blood component transfusion (including red cells, plasma and platelets). They regard non-consensual transfusion as a physical violation. Consent to treatment is at the heart of this guideline. Refusal of treatment by an adult with capacity is lawful. The reasons why a patient might refuse transfusion and the implications are examined. The processes and products that are deemed acceptable or unacceptable to Jehovah's Witnesses are described. When a team is faced with a patient who refuses transfusion, a thorough review of the clinical situation is advocated and all options for treatment should be explored. After discussion, a plan should then be made that is acceptable to the patient and appropriate consent obtained. When agreement cannot be reached between the doctor and the patient, referral for a second opinion should be considered. When the patient is a child, the same strategy should be used but on occasion the clinical team may have to obtain legal help.

Utilizing simulated errors in radiotherapy plans to quantify the effectiveness of the physics plan review.

PURPOSE: The review of a radiation therapy plan by a physicist prior to treatment is a standard tool for ensuring the quality of treatments. However, little is known about how well this task is performed in practice. The goal of this study is to present a novel method to measure the effectiveness of physics plan review by introducing simulated errors into computerized "mock" treatment charts and measuring the performance of plan review by physicists. METHODS: We generated six simulated treatment charts containing multiple errors. To select errors, we compiled a list based on events from a departmental incident learning system and an international incident learning system (SAFRON). Seventeen errors with the highest scores for frequency and severity were included in the simulations included six mock treatment charts. Eight physicists reviewed the simulated charts as they would a normal pretreatment plan review, with each chart being reviewed by at least six physicists. There were 113 data points for evaluation. Observer bias was minimized using a simple error vs hidden error approach, using detectability scores for stratification. The confidence interval for the proportion of errors detected was computed using the Wilson score interval. RESULTS: Simulated errors were detected in 67% of reviews [58-75%] (95% confidence interval [CI] in brackets). Of the errors included in the simulated plans, the following error scenarios had the highest detection rates: an incorrect isocenter in DRR (93% [70-99%]), a planned dose different from the prescribed dose (92% [67-99%]) and invalid QA (85% [58-96%]). Errors with low detection rates included incorrect CT dataset (0%, [0-39%]) and incorrect isocenter localization in planning system (38% [18-64%]). Detection rates of errors from simulated charts were compared against observed detection rates of errors from a departmental incident learning system. CONCLUSIONS: It has been notoriously difficult to quantify error and safety performance in oncology. This study uses a novel technique of simulated errors to quantify performance and suggests that the pretreatment physics plan review identifies some errors with high fidelity while other errors are more challenging to detect. These data will guide future work on standardization and automation. The example process studied here was physics plan review, but this approach of simulated errors may be applied in other contexts as well and may also be useful for training and education purposes.

Futureproofing [18F]Fludeoxyglucose manufacture at an Academic Medical Center.

BACKGROUND: We recently upgraded our [18F]fludeoxyglucose (FDG) production capabilities with the goal of futureproofing our FDG clinical supply, expanding the number of batches of FDG we can manufacture each day, and improving patient throughput in our nuclear medicine clinic. In this paper we report upgrade of the synthesis modules to the GE FASTLab 2 platform (Phase 1) and cyclotron updates (Phase 2) from both practical and regulatory perspectives. We summarize our experience manufacturing FDG on the FASTLab 2 module with a high-yielding self-shielded niobium (Nb) fluorine-18 target. RESULTS: Following installation of Nb targets for production of fluorine-18, a 55 µA beam for 22 min generated 1330 ± 153 mCi of [18F]fluoride. Using these cyclotron beam parameters in combination with the FASTLab 2, activity yields (AY) of FDG were 957 ± 102 mCi at EOS, corresponding to 72% non-corrected AY (n = 235). Our workflow, inventory management and regulatory compliance have been greatly simplified following the synthesis module and cyclotron upgrades, and patient wait times for FDG PET have been cut in half at our nuclear medicine clinic. CONCLUSIONS: The combination of FASTlab 2 and self-shielded Nb fluorine-18 targets have improved our yield of FDG, and enabled reliable and repeatable manufacture of the radiotracer for clinical use.