Most antiviral and anticancer nucleosides are prodrugs that require stepwise phosphorylation to their triphosphate nucleotide form for biological activity. Monophosphorylation may be rate-limiting, and the nucleotides may be unstable and poorly internalized by target cells. Effective targeting and delivery systems for nucleoside drugs, including oligonucleotides used in molecular therapeutics, could augment their efficacy. The development of a carrier designed to effect selective transmembrane internalization of nucleotides via the asialoglycoprotein receptor (ASGPr) is now reported. In this work, the polycationic, polygalactosyl drug delivery carrier heptakis[6-amino-6-deoxy-2-O-(3-(1-thio-β-D-galactopyranosyl)-propyl)]-β-cyclodextrin hepta-acetate salt (GCyDAc), potentially a bifunctional carrier of (poly)nucleotides, was modeled by molecular docking in silico as an ASGPr-ligand, then synthesized for testing. The antivirals arabinosyl adenine (araA, vidarabine, an early generation antiviral nucleoside), arabinosyl adenine 5′-monophosphate (araAMP), and 12-mer-araAMP (p-araAMP) were selected for individual formulation with GCyDAc to develop this concept. Experimentally, beta cyclodextrin was decorated with seven protonated amino substituents on the primary face, and seven thiogalactose residues on its secondary face. AraA, araAMP, and p-araAMP were individually complexed with GCyDAc and complex formation for each drug was confirmed by differential scanning calorimetry (DSC). Finally, the free drugs and their GCyDAc complexes were evaluated for antiviral activity using ASGPr-expressing HepAD38 cells in cell culture. In this model, araA, araAMP, and p-araAMP showed relative antiviral potencies of 1.0, 1.1, and 1.2, respectively. In comparison, GCyDAc-complexes of araA, araAMP, and p-araAMP were 2.5, 1.3, and 1.2 times more effective than non-complexed araA in suppressing viral DNA production. The antiviral potencies of these complexes were minimally supportive of the hypothesis that ASGPr-targeted, CyD-based charge-association complexation of nucleosides and nucleotides could effectively enhance antiviral efficacy. GCyDAc was non-toxic to mammalian cells in cell culture, as determined using the MTS proliferation assay.

Cellular adaptations to hypoxia promote resistance to ionizing radiation (IR). This presents a challenge for treatment of head and neck cancer (HNC) that relies heavily on radiotherapy. Standard radiosensitizers often fail to reach diffusion-restricted hypoxic cells, whereas nitroimidazoles (NIs) [such as iodoazomycin arabinofuranoside (IAZA) and fluoroazomycin arabinofuranoside (FAZA)] can preferentially accumulate in hypoxic tumours. Here, we explored if the hypoxia-selective uptake of IAZA and FAZA could be harnessed to make HNC cells (FaDu) susceptible to radiation therapy. Cellular response to treatment was assessed through clonogenic survival assays and by monitoring DNA damage (immunofluorescence staining of DNA damage markers, γ-H2AX and p-53BP1, and by alkaline comet assay). The effects of reoxygenation were studied using the following assays: estimation of nucleoside incorporation to assess DNA synthesis rates, immunofluorescent imaging of chromatin-associated replication protein A as a marker of replication stress, and quantification of reactive oxygen species (ROS). Both IAZA and FAZA sensitized hypoxic HNC cells to IR, albeit the former is a better radiosensitizer. Radiosensitization by these compounds was restricted only to hypoxic cells, with no visible effects under normoxia. IAZA and FAZA impaired cellular adaptation to reoxygenation; high levels of ROS, reduced DNA synthesis capacity, and signs of replication stress were observed in reoxygenated cells. Overall, our data highlight the therapeutic potentials of IAZA and FAZA for targeting hypoxic HNC cells and provide rationale for future preclinical studies.

Theragnostic pairs of isotopes are used to infer radiation dosimetry for a therapeutic radiopharmaceutical from a diagnostic imaging study with the same tracer molecule labelled with an isotope better suited for the imaging task. We describe the transfer of radiation dosimetry from the diagnostic radioiodine isotope 123I, labelled for the hypoxia tracer molecule iodoazomycin arabinoside ([123I]IAZA), to isotopes 131I (therapeutic) and 124I (PET imaging). Uncertainties introduced by the dissimilar isotope half-lives are discussed in detail. Radioisotope dosimetries for [123I]IAZA were obtained previously. These data are used here to calculate residence times for 131I and 124I and their uncertainties. We distinguish two cases when extrapolating to infinity: purely physical decay (case A) and physical decay plus biological washout (case B). Organ doses were calculated using the MIRD schema with the OLIDNA/EXM code. Significant increases in some organ doses (in mSv per injected activity) were found for 131I and 124I. The most affected organs were the intestinal walls, thyroid, and urinary bladder wall. Uncertainty remained similar to 123I for case A but considerably greater for case B, especially for long biological half-lives (GI tract). Normal tissue dosimetries for IAZA must be considered carefully when substituting isotope species. A long biological half-life can significantly increase dosimetric uncertainties. These findings are relevant when considering PET imaging studies with [124I]IAZA or therapeutic administration of [131I]IAZA.

Solid tumours are often poorly oxygenated, which confers resistance to standard treatment modalities. Targeting hypoxic tumours requires compounds, such as nitroimidazoles (NIs), equipped with the ability to reach and become activated within diffusion limited tumour niches. NIs become selectively entrapped in hypoxic cells through bioreductive activation, and have shown promise as hypoxia directed therapeutics. However, little is known about their mechanism of action, hindering the broader clinical usage of NIs. Iodoazomycin arabinofuranoside (IAZA) and fluoroazomycin arabinofuranoside (FAZA) are clinically validated 2-NI hypoxic radiotracers with excellent tumour uptake properties. Hypoxic cancer cells have also shown preferential susceptibility to IAZA and FAZA treatment, making them ideal candidates for an in-depth study in a therapeutic setting. Using a head and neck cancer model, we show that hypoxic cells display higher sensitivity to IAZA and FAZA, where the drugs alter cell morphology, compromise DNA replication, slow down cell cycle progression and induce replication stress, ultimately leading to cytostasis. Effects of IAZA and FAZA on target cellular macromolecules (DNA, proteins and glutathione) were characterized to uncover potential mechanism(s) of action. Covalent binding of these NIs was only observed to cellular proteins, but not to DNA, under hypoxia. While protein levels remained unaffected, catalytic activities of NI target proteins, such as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the detoxification enzyme glutathione S-transferase (GST) were significantly curtailed in response to drug treatment under hypoxia. Intraperitoneal administration of IAZA was well-tolerated in mice and produced early (but transient) growth inhibition of subcutaneous mouse tumours.

Vitamin E, a natural antioxidant, is of interest to scientists, health care pundits and faddists; its nutritional and biomedical attributes may be validated, anecdotal or fantasy. Vitamin E is a mixture of tocopherols (TPs) and tocotrienols (T-3s), each class having four substitutional isomers (α-, β-, γ-, δ-). Vitamin E analogues attain only low concentrations in most tissues, necessitating exacting invasive techniques for analytical research. Quantitative positron emission tomography (PET) with an F-18-labeled molecular probe would expedite access to Vitamin E’s biodistributions and pharmacokinetics via non-invasive temporal imaging. (R)-6-(3-[18F]Fluoropropoxy)-2,7,8-trimethyl-2-(4,8,12-trimethyltrideca-3,7,11-trien-1-yl)-chromane ([18F]F-γ-T-3) was prepared for this purpose. [18F]F-γ-T-3 was synthesized from γ-T-3 in two steps: (i) 1,3-di-O-tosylpropane was introduced at C6-O to form TsO-γ-T-3, and (ii) reaction of this tosylate with [18F]fluoride in DMF/K222. Non-radioactive F-γ-T-3 was synthesized by reaction of γ-T-3 with 3-fluoropropyl methanesulfonate. [18F]F-γ-T-3 biodistribution in a murine tumor model was imaged using a small-animal PET scanner. F-γ-T-3 was prepared in 61% chemical yield. [18F]F-γ-T-3 was synthesized in acceptable radiochemical yield (RCY 12%) with high radiochemical purity (>99% RCP) in 45 min. Preliminary F-18 PET images in mice showed upper abdominal accumulation with evidence of renal clearance, only low concentrations in the thorax (lung/heart) and head, and rapid clearance from blood. [18F]F-γ-T-3 shows promise as an F-18 PET tracer for detailed in vivo studies of Vitamin E. The labeling procedure provides acceptable RCY, high RCP and pertinence to all eight Vitamin E analogues.

The reduction potentials of bioreductively-activated drugs represent an important design parameter to be accommodated in the course of creating lead compounds and improving the efficacy of older generation drugs. Reduction potentials are traditionally reported as single–electron reduction potentials, E(1), measured against reference electrodes under strictly defined experimental conditions. More recently, computational chemists have described redox properties in terms of a molecule’s highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), in electron volts (eV). The relative accessibility of HOMO/LUMO data through calculation using today’s computer infrastructure and simplified algorithms make the calculated value (LUMO) attractive in comparison to the accepted but rigorous experimental determination of E(1). This paper describes the correlations of eV (LUMO) to E(1) for three series of bioreductively–activated benzotriazine di-N-oxides (BTDOs), ring-substituted BTDOs, ring-added BTDOs and a selection of aromatic nitro compounds. The current computational approach is a closed–shell calculation with a single optimization. Gas phase geometry optimization was followed by a single–point DFT (Density Functional Theory) energy calculation in the gas phase or in the presence of polar solvent. The resulting DFT–derived LUMO energies (eV) calculated for BTDO analogues in gas phase and in presence of polar solvent (water) exhibited very strong linear correlations with high computational efficiency (r2 = 0.9925) and a very high predictive ability (MAD = 7 mV and RMSD = 9 mV) when compared to reported experimentally determined single–electron reduction potentials.

Introduction: The redox characteristics of 1,2,4-benzotriazine-1,4-dioxides (BTDOs) make them potential radiosensitizing agents for hypoxic cells in solid human cancers. Tirapazamine (TPZ) is the most clinically tested BTDO radiosensitizer, despite its toxicity at effective doses. To date, no BTDOs have been developed as diagnostic markers of tissue hypoxia. Hypothesis: TPZ analogues with appropriate reporting groups can act as potential radiosensitizers and hypoxia selective diagnostics. Experimental and results: 3-Chloro-1,2,4-benzotriazine 1-oxide was substituted at the C3 position to afford 3-(2-hydroxyethoxyethyl)-amino-1,2,4-benzotriazine-1-oxide, which was oxidized to 3-(2-hydroxyethoxyethyl)-amino-1,2,4-benzotriazine-1,4-dioxide (HO-EOE-TPZ) or converted to 3-(2-tosyloxyethoxyethyl)-amino-1,2,4-benzotriazine-1,4-dioxide (Tos-EOE-TPZ). Tos-EOE-TPZ was intended for use as a synthon for preparing 3-(2-azidoethoxyethyl)-amino-1,2,4-benzotriazine-1,4-dioxide (N-3-EOE-TPZ) and 3-(2-iodoethoxyethyl)-amino-1,2,4-benzotriazine-1,4-dioxide (I-EOE-TPZ). The logP values (-0.69 to 0.61) for these molecules bracketed that of TPZ (-0.34). Cell line dependent cytotoxicities (IC50) in air were in the 10-100 mu M range, with Hypoxia Cytotoxicity Ratios (HCR; IC50-air/IC50-hypoxia) of 5-10. LUMO calculations indicated that these molecules are in the optimal redox range for radiosensitization, offering cell-line-specific Relative Radiosensitization Ratios (RRSR; SER/OER) of 0.58-0.88, compared to TPZ (0.67-0.76). Conclusion: The LUMO, IC50, HCR and RRSR values of 3-(2-substituted ethoxyethyl)-amino-1,2,4-benzotriazine-1,4-dioxides are similar to the corresponding values for TPZ, supporting the conclusion that these TPZ analogues are potentially useful as hypoxia-activated radiosensitizers. Further studies into their biodistributions in animal models are being pursued to determine the in vivo potential in hypoxia management. (C) 2019 Elsevier Masson SAS. All rights reserved.

Introduction: Benzotriazine-1,4-dioxides (BTDOs) such as tirapazamine (TPZ) and its derivatives act as radiosensitizers of hypoxic tissues. The benzotriazine-1-monoxide (BTMO) metabolite (SR 4317, TPZMO) of TPZ also has radiosensitizing properties, and via unknown mechanisms, is a potent enhancer of the radiosensitizing effects of TPZ. Unlike their 2-nitroimidazole radiosensitizer counterparts, radiolabeled benzotriazine oxides have not been used as radiopharmaceuticals for diagnostic imaging or molecular radiotherapy (MRT) of hypoxia. The radioiodination chemistry for preparing model radioiodinated BTDOs and BTMOs is now reported. Hypothesis: Radioiodinated 3-(2-iodoethoxyethyl)-amino-1,2,4-benzotriazine-1,4-dioxide (I-EOE-TPZ), a novel bioisosteric analogue of TPZ, and 3-(2-iodoethoxyethyl)-amino-1,2,4-benzotriazine-1-oxide (I-EOE-TPZMO), its monoxide analogue, are candidates for in vivo and in vitro investigations of biochemical mechanisms in pathologies that develop hypoxic microenvironments. In theory, both radiotracers can be prepared from the same precursors. Methods: Radioiodination procedures were based on classical nucleophilic [131I]iodide substitution on Tos-EOE-TPZ (P1) and by [131I]iodide exchange on I-EOE-TPZ (P2). Reaction parameters, including temperature, reaction time, solvent and the influence of pivalic acid on products' formation and the corresponding radiochemical yields (RCY) were investigated. Results: The [131I]iodide labeling reactions invariably led to the synthesis of both products, but with careful manipulation of conditions the preferred product could be recovered as the major product. Radioiodide exchange on P2 in ACN at 80 ± 5 °C for 30 min afforded the highest RCY, 89%, of [131I]I-EOE-TPZ, which upon solid phase purification on an alumina cartridge gave 60% yield of the product with over 97% of radiochemical purity. Similarly, radioiodide exchange on P2 in ACN at 50 ± 5 °C for 30 min with pivalic acid afforded the highest yield, 92%, of [131I]I-EOE-TPZMO exclusively with no trace of [131I]I-EOE-TPZ. In both cases, extended reaction times and/or elevated temperatures resulted in the formation of at least two additional radioactive reaction products. Conclusions: Radioiodination of P1 and P2 with [131I]iodide leads to the facile formation of [131I]I-EOE-TPZMO. At 80 °C and short reaction times, the facile reduction of the N-4-oxide moiety was minimized to afford acceptable radiochemical yields of [131I]I-EOE-TPZ from either precursor. Regeneration of [131I]I-EOE-TPZ from [131I]I-EOE-TPZMO is impractical after reaction work-up.

The objective of this work is to evaluate the potential effect of cardiac stress exercise on 16 the accumulation of [123I]IAZA, a radiopharmaceutical used to image focal tissue hypoxia, in 17 otherwise normal myocardium in healthy volunteers, and to determine the impact of exercise on 18 [123I]IAZA pharmacokinetics. The underlying goal is to establish a rational basis and a baseline for 19 studies of focal myocardial hypoxia in cardiac patients using [123I]IAZA. Three healthy male 20 volunteers ran the ‘Bruce’ treadmill protocol, a clinically-accepted protocol designed to expose 21 myocardial ischemia in patients. The ‘Bruce’ criterion heart rate is 85% of [220 – age]. 22 Approximately one minute before reaching this level, [123I]IAZA (5.0 mCi/0.85 mg) was 23 administered as a slow (1–3 min) single intravenous (i.v.) injection via an indwelling venous 24 catheter. The volunteer continued running for an additional 1 min before being transferred to a 25 gamma camera. Serum samples were collected from the arm contralateral to the administration site 26 at pre-determined intervals from 1 min to 45 h post injection and were analyzed by radio HPLC. 27 Pharmacokinetic (PK) parameters were derived for [123I]IAZA and total radioactivity (total[123I]) 28 using compartmental and noncompartmental analyses. Whole-body planar scintigraphic images 29 were acquired from 0.75 to 24 h after dosing. PK data and scintigraphic images were compared to 30 previously published [123I]IAZA data from healthy volunteers rest. Following exercise stress, both 31 [123I]IAZA and total[123I] exhibited bi-exponential decline profiles, with rapid distribution phases 32 [half-lives (t1/2α) of 1.2 and 1.4 min, respectively], followed by slower elimination phases [t1/2β of 195 33 and 290 min, respectively]. Total body clearance (CLTB) and the steady state volume of 34 distribution (Vss) were 0.647 L/kg and 185 mL/min, respectively, for [123I]IAZA and 0.785 L/kg and 35 135 mL/min, respectively, for total[123I]. The t1/2β, CLTB and Vss values were comparable to those 36 reported previously for rested volunteers. The t1/2α was approximately 4-fold shorter for [123I]IAZA 37 and approximately 3-fold shorter for total[123I] under exercise relative to rested subjects. The heart 38 region was visualized in early whole body scintigraphic images, but later images showed no 39 accumulated radioactivity in this region, and no differences from images reported for rested 40 volunteers were apparent. Minimal uptake of radiotracer in myocardium and skeletal muscle was 41 consistent with uptake in non-stressed myocardium. Whole-body scintigrams for [123I]IAZA in 42 exercise-stressed healthy volunteers were indistinguishable from images of non-exercised 43 volunteers. There was no evidence of hypoxia-dependent binding in exercised but otherwise 44 Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 24 February 2018 doi:10.20944/preprints201710.0034.v2 © 2018 by the author(s). Distributed under a Creative Commons CC BY license. healthy myocardium, supporting the conclusion that exercise stress at Bruce protocol intensity 45 does not induce measurable myocardial hypoxia. Effects of exercise on PK parameters were 46 minimal; specifically, the t1/2α was shortened, reflecting increased cardiac output associated with 47 exercise. It is concluded that because [123I]IAZA was not metabolically bound in exercise-stressed 48 myocardium, a stress test will not create elevated myocardial background that would mask regions 49 of myocardial perfusion deficiency. [123I]IAZA would therefore be suitable for the detection of 50 viable, hypoxic myocardium in patients undergoing stress-test-based diagnosis. 51

Background: 1-α-D-(5-Deoxy-5-[18F]fluoroarabinofuranosyl)-2-nitroimidazole ([18F]FAZA) is manufactured by nucleophilic radiofluorination of 1-α-D-(2’,3’-di-O-acetyl-5’-O-toluenesulfonylarabinofuranosyl)- 2-nitroimidazole (DiAcTosAZA) and alkaline deprotection to afford [18F]FAZA. High yields (>60%) under optimized conditions frequently revert to low yields (<20%) in large scale, automated syntheses. Competing side reactions and concomitant complex reaction mixtures contribute to substantial loss of product during HPLC clean-up. Objective: To develop alternative precursors for facile routine clinical manufacture of [18F]FAZA that are compatible with current equipment and automated procedures. Methods: Two new precursors, 1-α-D-(2’,3’-di-O-acetyl-5’-O-(4-nitrobenzene)sulfonyl-arabinofuranosyl)-2- nitroimidazole (DiAcNosAZA) and 1-α-D-(2’,3’-di-O-acetyl-5’-iodo-arabinofuranosyl)-2-nitroimidazole (DiAcIAZA), were synthesized from commercially-available 1-α-D-arabinofuranosyl-2-nitroimidazole (AZA). A commercial automated synthesis unit (ASU) was used to condition F-18 for anhydrous radiofluorination, and to radiofluorinate DiAcNosAZA and DiAcIAZA using the local standardized protocol to manufacture [18F]FAZA from AcTosAZA. Results: DiAcNosAZA was synthesized via two pathways, in recovered yields of 29% and 40%, respectively. The nosylation of 1-α-D-(2’,3’-di-O-acetyl-arabinofuranosyl)-2-nitroimidazole (DiAcAZA) featured a strong competing reaction that afforded 1-α-D-(2’,3’-di-O-acetyl-5’-chloro-arabinofuranosyl)-2- nitroimidazole (DiAcClAZA) in 55% yield. Radiofluorination yields were better from DiAcNosAZA and DiAcIAZA than from DiAcTosAZA, and the presence of fewer side products afforded higher purity [18F]FAZA preparations. Several radioactive and non-radioactive by products of radiofluorination were assigned tentative chemical structures based on co-chromatography with authentic reference compounds. Conclusion: DiAcClAZA, a major side-product in the preparation of DiAcNosAZA, and its deprotected analogue (ClAZA), are unproven hypoxic tissue radiosensitizers. DiAcNosAZA and DiAcIAZA provided good radiofluorination yields in comparison to AcTosAZA and could become preferred [18F]FAZA precursors if the cleaner reactions can be exploited to bypass HPLC purification.

PURPOSE:Pharmacokinetic (PK) data are generally derived from blood samples withdrawn serially over a defined period after dosing. In small animals, blood sampling after dosing presents technical difficulties, particularly when short time intervals and frequent sampling are required. Positron emission tomography (PET) is a non-invasive functional imaging technique that can provide semi-quantitative temporal data for defined volume regions of interest (vROI), to support kinetic analyses in blood and other tissues. The application of preclinical small-animal PET to determine and compare PK parameters for [18F]FDG and [18F]FAZA, radiopharmaceuticals used clinically for assessing glucose metabolism and hypoxic fractions, respectively, in the same mammary EMT6 tumor-bearing mouse model, is reported here.METHODS:Two study groups were used: normal BALB/c mice under isoflurane anesthesia were intravenously injected with either [18F]FDG or [18F]FAZA. For the first group, blood-sampling by tail artery puncture was used to collect blood samples which were then analyzed with Radio-microTLC. Dynamic PET experiments were performed with the second group of mice and analyzed for blood input function and tumor uptake utilizing a modified two compartment kinetic model. Heart and inferior vena cava vROIs were sampled to obtain image-derived data. PK parameters were calculated from blood samples and image-derived data. Time-activity curves (TACs) were also generated over regions of liver, kidney and urinary bladder to depict clearance profiles for each radiotracer.RESULTS:PK values generated by classical blood sampling and PET image-derived analysis were comparable to each other for both radiotracers. Heart vROI data were suitable for analysis of [18F]FAZA kinetics, but metabolic uptake of radioactivity mandated the use of inferior vena cava vROIs for [18F]FDG analysis. While clearance (CL) and blood half-life (t½) were similar for both [18F]FDG and [18F]FAZA for both sampling methods, volume of distribution yielded larger differences, indicative of limitations such as partial volume effects within quantitative image-derived data. [18F]FDG underwent faster blood clearance and had a shorter blood half-life than [18F]FAZA. Kinetic analysis of tumor uptake from PET image data showed higher uptake and longer tumor tissue retention of [18F]FDG, indicative of the tumor's glucose metabolism rate, versus lower tumor uptake and retention of [18F]FAZA. While [18F]FAZA possesses a somewhat greater hepatobiliary clearance , [18F]FDG clears faster through the renal system which results in faster radioactivity accumulation in the urinary bladder.CONCLUSIONS:The present study provides a working example of the applicability of functional PET imaging as a suitable tool to determine PK parameters in small animals. The comparative analysis in the current study demonstrates that it is feasible to use [18F]FDG PET and [18F]FAZA PET in the same model to analyze their blood PK parameters, and to estimate kinetic parameters for these tracers in tumor. This non-invasive imaging-based determination of tissue kinetic parameters facilitates translation from pre-clinical to clinical phases of drug development. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

The objective of this work is to evaluate the potential effect of cardiac stress exercise on the accumulation of [123I]IAZA, a radiopharmaceutical used to image focal tissue hypoxia, in otherwise normal myocardium in healthy volunteers, and to determine the impact of exercise on [123I]IAZA pharmacokinetics. The underlying goal is to establish a rational basis and a baseline for studies of focal myocardial hypoxia in cardiac patients using [123I]IAZA. Three healthy male volunteers ran the ‘Bruce’ treadmill protocol, a clinically-accepted protocol designed to expose myocardial ischemia in patients. The ‘Bruce’ criterion heart rate is 85% of [220 – age]. Approximately one minute before reaching this level, [123I]IAZA (5.0 mCi/0.85 mg) was administered as a slow (1–3 min) single intravenous (i.v.) injection via an indwelling venous catheter. The volunteer continued running for an additional 1 min before being transferred to a gamma camera. Serum samples were collected from the arm contralateral to the administration site at pre-determined intervals from 1 min to 45 h post injection and were analyzed by radio HPLC. Pharmacokinetic (PK) parameters were derived for [123I]IAZA and total radioactivity (total[123I]) using compartmental and noncompartmental analyses. Whole-body planar scintigraphic images were acquired from 0.75 to 24 h after dosing. PK data and scintigraphic images were compared to previously published [123I]IAZA data from healthy volunteers rest. Following exercise stress, both [123I]IAZA and total[123I] exhibited bi-exponential decline profiles, with rapid distribution phases [half-lives (t1/2α) of 1.2 and 1.4 min, respectively], followed by slower elimination phases [t1/2β of 195 and 290 min, respectively]. Total body clearance (CLTB) and the steady state volume of distribution (Vss) were 0.647 L/kg and 185 mL/min, respectively, for [123I]IAZA and 0.785 L/kg and 135 mL/min, respectively, for total[123I]. The t1/2β, CLTB and Vss values were comparable to those reported previously for rested volunteers. The t1/2α was approximately 4-fold shorter for [123I]IAZA and approximately 3-fold shorter for total[123I] under exercise relative to rested subjects. The heart region was visualized in early whole body scintigraphic images, but later images showed no accumulated radioactivity in this region, and no differences from images reported for rested volunteers were apparent. Minimal uptake of radiotracer in myocardium and skeletal muscle was consistent with uptake in non-stressed myocardium. Whole-body scintigrams for [123I]IAZA in exercise-stressed healthy volunteers were indistinguishable from images of non-exercised volunteers. There was no evidence of hypoxia-dependent binding in exercised but otherwise healthy myocardium, supporting the conclusion that exercise stress at Bruce protocol intensity does not induce measurable myocardial hypoxia. Effects of exercise on PK parameters were minimal; specifically, the t1/2α was shortened, reflecting increased cardiac output associated with exercise. It is concluded that because [123I]IAZA was not metabolically bound in exercise-stressed myocardium, a stress test will not create elevated myocardial background that would mask regions of myocardial perfusion deficiency. [123I]IAZA would therefore be suitable for the detection of viable, hypoxic myocardium in patients undergoing stress-test-based diagnosis.

Background: 1-alpha- D-(5-Deoxy-5-[F-18] fluoroarabinofuranosyl)-2-nitroimidazole([F-18] FAZA) is a PET radiotracer that demonstrates excellent potential in imaging regional hypoxia, and is clinically used in diagnosing a wide range of solid tumors in cancer patients. [F-18] FAZA, however, is radiofluorinated in only moderate recovered radiochemical yield (rRCY, similar to 12%). It is postulated that the relative stability of the C1' beta-anomeric bond at C5' will make 1-beta-D-(5-fluoro-5-deoxyarabinofuranosyl)-2-nitroimidazole (beta-FAZA), the beta-conformer of FAZA, an attractive candidate for clinical hypoxia imaging. Objectives: The principle goals were to synthesize beta-FAZA and beta-Ac(2)TsAZA, the radiofluorination precursor, to establish the radiofluorination chemistry leading to beta-[F-18] FAZA, and to investigate the biodistribution of beta-[F-18] FAZA in an animal tumor-bearing model using PET imaging. Methods: The appropriately-protected furanose sugar was coupled with 2-nitroimidazole to afford 1-beta-D-(2,3-di-O-acetylarabinofuranosyl)-2-nitroimidazole (beta-Ac(2)AZA). Fluorination of beta-Ac(2)AZA with DAST, followed by alkaline hydrolysis, afforded beta-FAZA (21%). The radiolabeling synthon, 1-beta-D-(5-O-toluenesulfonyl-2,3-di-O-acetylarabinofuranosyl)-2-nitroimidazole (beta-Ac(2)TsAZA), on radiofluorination using the F-18/K-222 complex under various reaction conditions, followed by base-catalyzed deacetylation, afforded beta-[F-18] FAZA. beta-[F-18] FAZA was radiochemically stable for at least 8 h when stored in aqueous ethanol (8%) at 22 degrees C. A preliminary PET imaging-based biodistribution study of beta-[F-18] FAZA was performed in A431 tumor-bearing nude mice. Results: beta-FAZA and beta-Ac(2)TsAZA were synthesized in satisfactory yield. Radiochemistry of [F-18] FAZA was established. PET images showed strong uptake in hypoxic regions of the tumor. Conclusion: The synthesis of beta-FAZA and -beta[F-18] FAZA are reported. Radiofluorination of beta-Ac(2)TsAZA and the deprotection of -beta Ac-2[F-18] FAZA were facile, but led to a more complex mixture of radiofluorinated by-products than observed with the corresponding precursor of beta-[F-18] FAZA. PET images were indicative of hypoxia-selective accumulation of beta-[F-18] FAZA in tumor.

BACKGROUND:1-α-D-(5-Deoxy-5-[18F]fluoroarabinofuranosyl)-2-nitroimidazole([18F] FAZA) is a PET radiotracer that demonstrates excellent potential in imaging regional hypoxia, and is clinically used in diagnosing a wide range of solid tumors in cancer patients. [18F]FAZA, however, is radiofluorinated in only moderate recovered radiochemical yield (rRCY, ~12%). It is postulated that the relative stability of the C1' β-anomeric bond at C5' will make 1-β-D-(5-fluoro-5-deoxyarabinofuranosyl)-2-nitroimidazole (β-FAZA), the β-conformer of FAZA, an attractive candidate for clinical hypoxia imaging.OBJECTIVES:The principle goals were to synthesize β-FAZA and β-Ac2TsAZA, the radiofluorination precursor, to establish the radiofluorination chemistry leading to β-[18F]FAZA, and to investigate the biodistribution of β-[18F]FAZA in an animal tumor-bearing model using PET imaging.METHODS:The appropriately-protected furanose sugar was coupled with 2-nitroimidazole to afford 1-β-D-(2,3-di-O-acetylarabinofuranosyl)-2-nitroimidazole (β-Ac2AZA). Fluorination of β-Ac2AZA with DAST, followed by alkaline hydrolysis, afforded β-FAZA (21%). The radiolabeling synthon, 1-β-D-(5-O-toluenesulfonyl-2,3-di-O-acetylarabinofuranosyl)-2-nitroimidazole (β-Ac2TsAZA), on radiofluorination using the 18F/K222 complex under various reaction conditions, followed by base-catalyzed deacetylation, afforded β-[18F]FAZA. β-[18F]FAZA was radiochemically stable for at least 8 h when stored in aqueous ethanol (8%) at 22 °C. A preliminary PET imaging-based biodistribution study of β-[18F]FAZA was performed in A431 tumor-bearing nude mice.RESULTS:β-FAZA and β-Ac2TsAZA were synthesized in satisfactory yield. Radiochemistry of [18F]FAZA was established. PET images showed strong uptake in hypoxic regions of the tumor.CONCLUSION:The synthesis of β-FAZA and β-[18F]FAZA are reported. Radiofluorination of β-Ac2TsAZA and the deprotection of β-Ac2[18F]FAZA were facile, but led to a more complex mixture of radiofluorinated by-products than observed with the corresponding precursor of α-[18F]FAZA. PET images were indicative of hypoxia-selective accumulation of β-[18F]FAZA in tumor.

Background. 1--D-(5-Deoxy-5-[ 18 F]fluoroarabinofuranosyl)-2-nitroimidazole ([ 18 F]FAZA) is a PET radiotracer currently used to image regional hypoxia in a wide range of solid tumors in cancer patients. [ 18 F]FAZA is radiofluorinated in moderate recovered radiochemical yield (rRCY) via nucleophilic substitution of the 1-α-D-(2,3-di-O-acetyl-5-tosyl)-AZA precursor. Hypothesis. It is postulated that the β-conformer of FAZA, 1--D-(5-fluoro-5-deoxyarabinofuranosyl)2-nitroimidazole (β-FAZA), by dint of the relative stability of the C1’ β-anomeric bond to basecatalysed hydrolysis and / or the fidelity of nucleophilic substitution at C5’, may offer improved rRCY. Preliminary PET images of the biodistribution of -[ 18 F]FAZA in a hypoxic tumor-bearing animal

There is increasing demand, from both engineers and their clients, for structures that can be rapidly returned to occupancy following an earthquake, while also maintaining or reducing initial costs. One possible way towards this goal is to ensure that seismic damage occurs only within elements that can be removed and replaced following a damaging earthquake. For concentrically braced frames that use hollow structural sections, the current design practice requires field welding of the brace to the gusset in a way that causes the brace to buckle out-of-plane. In the event of a damaging earthquake, the out-of-plane brace buckling may damage both the gusset plate and also any adjacent exterior cladding. The plate cannot be easily replaced, resulting in expensive and time-consuming repairs, and the damaged cladding could endanger the lives of people evacuating the building and of other pedestrians. This paper discusses the development of an alternative connection that can be bolted into place and that confines damage to replaceable components. The proposed connection is expected to result in reduced erection costs and be easier to repair following a major earthquake. Moreover, the new connection causes buckling to occur in plane, preventing dangerous damage to the cladding. Potential challenges in the design of such a connection are discussed and evaluated, and a finite element model that was created to confirm the performance of the proposed connection is also introduced. Finally, future areas of research and development of the connection are identified.

Iodoglucoazomycin (I‐GAZ; N‐(2‐iodo‐3‐(6‐O‐glucosyl)propyl)‐2‐nitroimidazole), a non‐glycosidic nitroimidazole–6‐O‐glucose adduct, was synthesized, radioiodinated, and evaluated as a substrate of glucose transporter 1 (GLUT1) for radiotheranostic (therapy+diagnostic) management of hypoxic tumors. Nucleophilic iodination of the nosylate synthon of I‐GAZ followed by deprotection afforded I‐GAZ in 74 % overall yield. I‐GAZ was radioiodinated via ‘exchange’ labeling using [123/131I]iodide (50–70 % RCY) and then purified by Sep‐Pak™ (>96 % RCP). [131I]I‐GAZ was stable in 2 % ethanolic solution in sterile water for 14 days when stored at 5 °C. In cell culture, I‐GAZ was found to be nontoxic to EMT‐6 cells at concentrations <0.5 mm, and weakly radiosensitizing (SER 1.1 at 10 % survival of EMT‐6 cells; 1.2 at 0.1 % survival in MCF‐7 cells). The hypoxic/normoxic uptake ratio of [123I]I‐GAZ in EMT‐6 cells was 1.46 at 2 h, and under normoxic conditions the uptake of [123I]I‐GAZ by EMT‐6 cells was unaltered in the presence of 5 mm glucose. The biodistribution of [131I]I‐GAZ in EMT‐6 tumor‐bearing Balb/c mice demonstrated rapid clearance from blood and extensive renal and hepatic excretion. Tumor/blood and tumor/muscle ratios reached ∼3 and 8, respectively, at 4 h post‐injection. Regression analysis of the first order polynomial plots of the blood and tumor radioactivity concentrations supported a perfusion–excretion model with low hypoxia‐dependent binding. [131I]I‐GAZ was found to be stable in vivo, and did not deiodinate.

Hypoxia is prevalent in many solid tumors. Hypoxic tumors tend to exhibit rapid growth and aberrant vasculature, which lead to oxygen (O2) depletion and impaired drug delivery. The reductive environment in hypoxic tumors alters cellular metabolism, which can trigger transcriptional responses; induce genetic alterations; promote invasion, metastasis, resistance to radiotherapy and chemotherapy, tumor progression, and recurrence; and leads to poor local control and reduced survival rates. Therefore, exploiting the reductive microenvironment in hypoxic tumors by delivering electron-affinic, O2-mimetic radioactive drugs that bioreductively activate selectively in the hypoxic microenvironment offers a logical approach to molecular imaging of focal hypoxia. Because these agents also radiosensitize hypoxic cells, they provide an innovative approach to the therapy management of such tumors. To date, nuclear imaging of hypoxic tumor has proven to be clinically effective, whereas chemical radiosensitization by these compounds has not been helpful. The current review provides an insight into the chemistry, radiochemistry, and purification strategies for selected nitroaromatics that directly exploit the bioreductive environment in hypoxic cells. Both experimental and calculated single-electron reduction potentials of electron-affinic compounds, nitroimidazoles in particular, correlate with in vitro radiosensitizing properties, making them preferred choices for use as radiopharmaceuticals for diagnostic imaging and as sensitizers to enhance the killing effects of low-energy-transfer x-rays (O2-mimetic radiosensitization). Extensive research and careful drug design have led to the development of several potentially useful hypoxia-targeting drugs, for example, [(18)F]FAZA, [(18)F]FMISO, [(18)F]EF5, and [(123)I]IAZA, that accrue selectively in hypoxic cells. These molecular probes are now globally used in clinical hypoxia imaging, including cancer. Future innovative developments must, however, consider hypoxia-selective molecular processes and the physicochemical properties of the drugs that dictate their biodistribution, hypoxia-selective accumulation, pharmacokinetics, clearance, biochemical behavior, and metabolism. This will facilitate their ultimate transformation to effective molecular theranostics, leading to improved multimodal management of cancer.

Oxygen supply - demand imbalances can render proliferating cells acutely or chronically hypoxic. In cancer cells, hypoxia-induced pathophysiological changes give rise to genetic changes that lead to treatment-resistant, aggressive phenotypes. The reduced curability of hypoxic tumours by radiotherapy is one of consequent challenges, but their hypoxia also offers unique, exploitable properties. Nitroimidazoles, for example, capitalize on oxygen-sensitive reductive activation to achieve hypoxiaselective localization for theranostic consequence. The discovery of 2-nitroimidazole (azomycin) heralded the development of many drugs, including effective radiosensitizers of hypoxic cells. These electron-affinic, reductively bioactivated nitroheterocyclics undergo initial oxygen-reversible, enzymatic one-electron reductions that lead to the formation of molecular adducts that impair vital

Hypoxia is prevalent in many solid tumors. Hypoxic tumors tend to exhibit rapid growth and aberrant vasculature, which lead to oxygen (O-2) depletion and impaired drug delivery. The reductive environment in hypoxic tumors alters cellular metabolism, which can trigger transcriptional responses; induce genetic alterations; promote invasion, metastasis, resistance to radiotherapy and chemotherapy, tumor progression, and recurrence; and leads to poor local control and reduced survival rates. Therefore, exploiting the reductive microenvironment in hypoxic tumors by delivering electron-affinic, O-2-mimetic radioactive drugs that bioreductively activate selectively in the hypoxic microenvironment offers a logical approach to molecular imaging of focal hypoxia. Because these agents also radiosensitize hypoxic cells, they provide an innovative approach to the therapy management of such tumors. To date, nuclear imaging of hypoxic tumor has proven to be clinically effective, whereas chemical radiosensitization by these compounds has not been helpful. The current review provides an insight into the chemistry, radiochemistry, and purification strategies for selected nitroaromatics that directly exploit the bioreductive environment in hypoxic cells. Both experimental and calculated single-electron reduction potentials of electron-affinic compounds, nitroimidazoles in particular, correlate with in vitro radiosensitizing properties, making them preferred choices for use as radiopharmaceuticals for diagnostic imaging and as sensitizers to enhance the killing effects of low-energy-transfer x-rays (O-2-mimetic radiosensitization). Extensive research and careful drug design have led to the development of several potentially useful hypoxia-targeting drugs, for example, [F-18]FAzA, [F-18]FMISO, [F-18]EF5, and [I-123]IAZA, that accrue selectively in hypoxic cells. These molecular probes are now globally used in clinical hypoxia imaging, including cancer. Future innovative developments must, however, consider hypoxia-selective molecular processes and the physicochemical properties of the drugs that dictate their biodistribution, hypoxia-selective accumulation, pharmacokinetics, clearance, biochemical behavior, and metabolism. This will facilitate their ultimate transformation to effective molecular theranostics, leading to improved multimodal management of cancer. (C) 2015 Elsevier Inc. All rights reserved.