Browsing by Author "Wyatt, NA"
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- Item[18F]Fluorination optimisation and the fully automated production of [18F]MEL050 using a microfluidic system(CSIRO Publishing, 2014-06-06) Matesic, L; Kallinen, A; Wyatt, NA; Pham, TQ; Greguric, ID; Pascali, GThe [18F]radiolabelling of the melanin-targeting positron-emission tomography radiotracer [18F]MEL050 was rapidly optimised using a commercial continuous-flow microfluidic system. The optimal [18F]fluorination incorporation conditions were then translated to production-scale experiments (35–150 GBq) suitable for preclinical imaging, complete with automated HPLC–solid phase extraction purification and formulation. [18F]MEL050 was obtained in 43 ± 10 % radiochemical yield in ~50 min. © 2015 CSIRO Publishing.
- ItemAscertaining the suitability of aryl sulfonyl fluorides for [18F]radiochemistry applications: a systematic investigation using microfluidics(American Chemical Society, 2013-10-18) Matesic, L; Wyatt, NA; Fraser, BH; Roberts, MP; Pham, TQ; Greguric, IDOptimization of [18F]radiolabeling conditions and subsequent stability analysis in mobile phase, PBS buffer, and rat serum of 12 aryl sulfonyl chloride precursors with various substituents (electron-withdrawing groups, electron-donating groups, increased steric bulk, heterocyclic) were performed using an Advion NanoTek Microfluidic Synthesis System. A comparison of radiochemical yields and reaction times for a microfluidics device versus a conventional reaction vessel is reported. [18F]Radiolabeling of sulfonyl chlorides in the presence of competing nucleophiles, H-bond donors, and water was also assessed and demonstrated the versatility and potential utility of [18F]sulfonyl fluorides as synthons for indirect radiolabeling. © 2013 American Chemical Society
- ItemComparative analysis of novel decynium-22 analogs to inhibit transport by the low-affinity, high-capacity monoamine transporters, organic cation transporters 2 and 3, and plasma membrane monoamine transporter(Elsevier B. V., 2019-01) Fraser-Spears, R; Krause-Heuer, AM; Basiouny, M; Mayer, FP; Manishimwe, M; Wyatt, NA; Dobrowolski, JC; Roberts, MP; Greguric, ID; Kumar, N; Koek, W; Sitte, HH; Callaghan, PD; Fraser, BH; Daws, LCGrowing evidence supports involvement of low-affinity/high-capacity organic cation transporters (OCTs) and plasma membrane monoamine transporter (PMAT) in regulating clearance of monoamines. Currently decynium-22 (D22) is the best pharmacological tool to study these transporters, however it does not readily discriminate among them, underscoring a need to develop compounds with greater selectivity for each of these transporters. We developed seven D22 analogs, and previously reported that some have lower affinity for α1-adrenoceptors than D22 and showed antidepressant-like activity in mice. Here, we extend these findings to determine the affinity of these analogs for OCT2, OCT3 and PMAT, as well as serotonin, norepinephrine and dopamine transporters (SERT, NET and DAT) using a combination of uptake competition with [3H]methyl-4-phenylpyridinium acetate in overexpressed HEK cells and [3H]citalopram, [3H]nisoxetine and [3H]WIN 35428 displacement binding in mouse hippocampal and striatal preparations. Like D22, all analogs showed greater binding affinities for OCT3 than OCT2 and PMAT. However, unlike D22, some analogs also showed modest affinity for SERT and DAT. Dual OCT3/SERT and/or OCT3/DAT actions of certain analogs may help explain their ability to produce antidepressant-like effects in mice and help account for our previous findings that D22 lacks antidepressant-like effects unless SERT function is either genetically or pharmacologically compromised. Though these analogs are not superior than D22 in discriminating among OCTs/PMAT, our findings point to development of compounds with combined ability to inhibit both low-affinity/high-capacity transporters, such as OCT3, and high-affinity/low-capacity transporters, such as SERT, as therapeutics with potentially improved efficacy for treatment of psychiatric disorders. © 2021 Elsevier B.V.
- ItemDifferential activity of decynium-22 analogs: novel targets for probing low-affinity/high-capacity biogenic amine transporters(Federation of American Societies for Experimental Biology (FASEB), 2015-04-01) Fraser, R; Owens, A; Wyatt, NA; Krause-Heuer, AM; Greguric, ID; Callaghan, PD; Fraser, BH; Daws, LCWe study neurotransmitter clearance by low-affinity, high-capacity uptake-2 transporters. This family includes plasma membrane monoamine transporter (PMAT) and three organic cation transporter isoforms (OCT1-3). We have shown uptake-2 transporters limit the effectiveness of the selective serotonin reuptake inhibitor (SSRI) fluvoxamine. Discerning the transporter type(s) involved is restricted by the lack of highly selective ligands. This project examines the pharmacological characteristics of novel uptake-2 compounds. Activity of ANSTO analogs, structurally based on the non-selective inhibitor decynium 22 (D22), was tested in human OCT3-HEK cells. Ligand competitions of [3H]MPP+ uptake were measured in whole, attached cells. Compared to D22, dose-responses of ANSTO compounds shifted 1- or 2 log-rightward, indicating reduced potency to inhibit OCT3 mediated [3H]MPP+ uptake. ANSTO analogs displayed similar potencies to corticosterone and may have higher selectivity at alternate uptake 2 subtypes. © 2015 Federation of American Societies for Experimental Biology (FASEB)
- ItemEvaluation of the antidepressant therapeutic potential of isocyanine and pseudoisocyanine analogues of the organic cation decynium-22(Elsevier B. V., 2017-09-08) Krause-Heuer, AM; Fraser-Spears, R; Dobrowolski, JC; Ashford, ME; Wyatt, NA; Roberts, MP; Gould, GG; Cheah, WC; Ng, CKL; Bhadbhade, MM; Zhang, B; Greguric, ID; Wheate, NJ; Kumar, N; Koek, W; Callaghan, PD; Daws, LC; Fraser, BHAntidepressant-like activity Herein we describe the synthesis and evaluation of antidepressant properties of seven analogues (1–7) of the low affinity/high capacity transporter blocker decynium-22 (D-22). All analogues (1–7) were synthesized via base promoted coupling reactions between N-alkylated-2-methylquinolinium iodides or N-alkylated-4-methylquinolinium iodides and electrophilic N-alkylated-2-iodoquinolinium iodides. All final compounds were purified by re-crystallization or preparative HPLC and initial evaluation studies included; 1) screening for in vitro α1-adrenoceptor activity (a property that can lead to unwanted side-effects), 2) measuring antidepressant-like activity in a mouse tail suspension test (TST), and 3) measuring effects upon mouse locomotion. The results showed some analogues have lower affinities at α1-adrenoceptors compared to D-22 and showed antidepressant-like activity without the need for co-administration of SSRIs. Additionally, many analogues did not affect mouse locomotion to the same extent as D-22. Plans for additional evaluations of these promising analogues, including measurement of antidepressant-like activity with co-administration of selective serotonin re-uptake inhibitors (SSRIs), are outlined. © 2017 Elsevier B.V.
- ItemFluorine-18 radiolabelling and in vitro / in vivo metabolism of [18F]D4-PBR111(John Wiley & Sons, Inc, 2019-05-26) Wyatt, NA; Safavi-Naeini, M; Wotherspoon, ATL; Arthur, A; Nguyen, AP; Parmar, A; Hamze, H; Day, CM; Zahra, D; Matesic, L; Davis, E; Rahardjo, GL; Yepuri, NR; Shepherd, R; Murphy, RB; Pham, TQ; Nguyen, VH; Callaghan, PD; Holden, PJ; Grégoire, MC; Darwish, TA; Fraser, BHObjectives The purinergic receptor P2X ligand-gated ion channel type 7 (P2X7R) is an adenosine triphosphate (ATP)-gated ion-channel, and P2X7R is a key player in inflammation. P2X7R is an emerging therapeutic target in central nervous system (CNS) diseases including Alzheimer's disease (AD) and Parkinson's disease (PD), because P2X7R also plays a pivotal role in neuroinflammation. P2X7R represents a potential molecular imaging target for neuroinflammation via biomedical imaging technique positron emission tomography (PET), and several radioligands targeting P2X7R have been developed and evaluated in animals. In our previous work, we have developed and characterized [11C]GSK1482160 as a P2X7R radioligand for neuroinflammation,2 clinical evaluation of [11C]GSK1482160 in healthy controls and patients is currently underway, and the estimation of radiation dosimetry for [11C]GSK1482160 in normal human subjects has been reported.3 Since the half-life (t1/2) of radionuclide carbon-11 is only 20.4 min, it is attractive for us to develop derivatives of [11C]GSK1482160, which can be labeled with the radionuclide fluorine-18 (t1/2, 109.7 min), and a fluorine-18 ligand would be ideal for widespread use.4 To this end, a series of [18F]fluoroalkyl including [18F]fluoromethyl (FM), [18F]fluoroethyl (FE), and [18F]fluoropropyl (FP) derivatives of GSK1482160 have been prepared and examined as new potential P2X7R radioligands. © 2019 The Authors
- ItemGd-TPP-DOTA reduces cell viability in cancer cells via synchrotron radiotherapy(Australian National University, 2021-08-24) Middleton, RJ; Howell, NR; Livio, E; Wyatt, NA; Chacon, A; Fraser, BH; Barnes, M; Cameron, M; Rendina, LM; Häusermann, D; Lerch, MLF; Safavi-Naeini, MHigh-Z elements have been proposed as radiosensitisers in X-ray photon radiotherapy due to their emission of multiple high-LET photo- and Auger electrons following X-ray irradiation. Gadolinium is a particularly attractive candidate radiosensitiser, since it can also be used as an MRI contrast agent. In this study, we report on the efficacy of Gd-triphenylphosphonium salt-DOTA (Gd(III)-TPP-DOTA) for synchrotron microbeam radiation therapy dose enhancement. The compound utilises the mitochondrial targeting moiety triphenylphosphonium (TPP) to accumulate Gd in the inner mitochondrial membrane. Experiments were conducted using the dynamic mode option at hutch 2B of the Imaging and Medical Beamline at the Australian Synchrotron. Human glioblastoma multiforme cells (T98G cell line) were cultured to 80-90% confluence in T12.5 flasks. Approximately 24 hours prior to irradiation, the cultures were either treated with a 500 μM solution of Gd(III)DOTA-TPP or a vehicle control. Spatial dose distribution of synchrotron broad beam (BB) and single/multiple microbeams were measured using a micron-scale X-Tream dosimetry system and Gafchromic films in air and at 2 cm depth in solid water (same depth as the monolayer of cells in T12.5 flasks). A total of 96 flasks were irradiated, with doses of 0, 1, 2, 3, 4, 5, 10 and 16 Gy delivered in valley (MRT) or uniformly (BB). Post irradiation, each flask was re-seeded into 7 x 96 well-plates to perform the resazurin cell proliferation assay up to 7 days after irradiation. Our preliminary analysis indicates that for cells irradiated by 3 Gy of BB or MRT radiation, the addition of Gd(III)DOTA-TPP results in a reduction in viable cell mass by 24.25% and 25.79%, respectively, compared with untreated flasks. © The Authors
- ItemHardware and software modifications on the Advion NanoTek microfluidic platform to extend flexibility for radiochemical synthesis(Elsevier Ltd., 2014-02) Pascali, G; Berton, A; DeSimone, M; Wyatt, NA; Matesic, L; Greguric, ID; Salvadori, PAMicrofluidic systems are currently receiving a lot of attention in the PET radiochemistry field, due to their demonstrated ability to obtain higher incorporation yields with reduced total processing time and using a decreased amount of precursors. The Advion NanoTek LF was the first commercial microfluidic system available for radiochemistry that allows basic parameter optimization to be performed. In this paper we report hardware and software modifications that would allow better performing procedures, higher product throughput and flexibility to utilize the system. In particular, HPLC purification and SPE formulation have been fully integrated. © 2014 Elsevier Ltd.
- ItemHigh levels of intravenous mephedrone (4-methylmethcathinone) self-administration in rats: neural consequences and comparison with methamphetamine(British Association for Psychopharmacology, 2013-06-05) Motbey, CP; Clemens, KJ; Apetz, N; Winstock, AR; Ramsey, J; Li, KM; Wyatt, NA; Callaghan, PD; Bowen, MT; Cornish, JL; McGregor, ISMephedrone (MMC) is a relatively new recreational drug that has rapidly increased in popularity in recent years. This study explored the characteristics of intravenous MMC self-administration in the rat, with methamphetamine (METH) used as a comparator drug. Male Sprague-Dawley rats were trained to nose poke for intravenous MMC or METH in daily 2 h sessions over a 10 d acquisition period. Dose-response functions were then established under fixed- and progressive-ratio (FR and PR) schedules over three subsequent weeks of testing. Brains were analyzed ex vivo for striatal serotonin (5-HT) and dopamine (DA) levels and metabolites, while autoradiography assessed changes in the regional density of 5-HT and serotonin transporter (SERT) and DA transporter (DAT) and induction of the inflammation marker translocator protein (TSPO). Results showed that MMC was readily and vigorously self-administered via the intravenous route. Under a FR1 schedule, peak responding for MMC was obtained at 0.1 mg/kg/infusion, versus 0.01 mg/kg/infusion for METH. Break points under a PR schedule peaked at 1 mg/kg/infusion MMC versus 0.3 mg/kg/infusion for METH. Final intakes of MMC were 31.3 mg/kg/d compared to 4 mg/kg/d for METH. Rats self-administering MMC, but not METH, gained weight at a slower rate than control rats. METH, but not MMC, self-administration elevated TSPO receptor density in the nucleus accumbens and hippocampus, while MMC, but not METH, self-administration decreased striatal 5-hydroxyindolacetic acid (5-HIAA) concentrations. In summary, MMC supported high levels of self-administration, matching or exceeding those previously reported with other drugs of abuse. Copyright © 2020 by British Association for Psychopharmacology
- ItemMephedrone in adolescent rats: residual memory impairment and acute but not lasting 5-HT depletion(PLOS, 2012-09-18) Motbey, CP; Karanges, E; Li, KM; Wilkinson, S; Winstock, AR; Ramsey, J; Hicks, C; Kendig, MD; Wyatt, NA; Callaghan, PD; McGregor, ISMephedrone (4-methylmethcathinone, MMC) is a popular recreational drug, yet its potential harms are yet to be fully established. The current study examined the impact of single or repeated MMC exposure on various neurochemical and behavioral measures in rats. In Experiment 1 male adolescent Wistar rats received single or repeated (once a day for 10 days) injections of MMC (30 mg/kg) or the comparator drug methamphetamine (METH, 2.5 mg/kg). Both MMC and METH caused robust hyperactivity in the 1 h following injection although this effect did not tend to sensitize with repeated treatment. Striatal dopamine (DA) levels were increased 1 h following either METH or MMC while striatal and hippocampal serotonin (5-HT) levels were decreased 1 h following MMC but not METH. MMC caused greater increases in 5-HT metabolism and greater reductions in DA metabolism in rats that had been previously exposed to MMC. Autoradiographic analysis showed no signs of neuroinflammation ([125I]CLINDE ligand used as a marker for translocator protein (TSPO) expression) with repeated exposure to either MMC or METH. In Experiment 2, rats received repeated MMC (7.5, 15 or 30 mg/kg once a day for 10 days) and were examined for residual behavioral effects following treatment. Repeated high (30 mg/kg) dose MMC produced impaired novel object recognition 5 weeks after drug treatment. However, no residual changes in 5-HT or DA tissue levels were observed at 7 weeks post-treatment. Overall these results show that MMC causes acute but not lasting changes in DA and 5-HT tissue concentrations. MMC can also cause long-term memory impairment. Future studies of cognitive function in MMC users are clearly warranted. © 2012 Motbey et al.
- ItemNovel decynium 22 analogs are potent and selective inhibitors of organic cation transporter-3(Springer, 2015-12-03) Fraser-Spears, R; Owens, WA; Wyatt, NA; Krause-Heuer, AM; Greguric, ID; Callaghan, PD; Fraser, BH; Koek, W; Daws, LCBackground: Low-affinity, high-capacity transporters for biogenic amines help regulate neurotransmitter homeostasis. They include the plasma membrane monoamine transporter (PMAT) and three organic cation transporter isoforms (OCT1-3). Our published data, using decynium-22 (D22), a non-selective blocker of PMAT and OCTs, suggests OCT3 and/or PMAT limit the therapeutic efficacy of selective serotonin reuptake inhibitors (SSRI). To aid in discerning the precise transporter(s) involved, we have characterized newly synthesized D22 analogs to identify PMAT and OCT isoform selective compounds. Methods: Effects of ANSTO analogs on locomotor activity and antidepressant-like behaviors were assessed in adult male, wild type (WT) mice using beam break measurements and the tail suspension test (TST). The activity of 7 analogs (ANSTO 301-307) to inhibit [3H]MPP+ uptake were measured in synaptosomes and HEK cells stably expressing human PMAT, OCT2 or OCT3. Results: Unlike D22, locomotor activity was not fully suppressed at higher doses up to 1.0 mg/kg, of ANSTO analogs 301, 303-306, and up to 10 mg/kg for ANSTO 307. Similarly to D22, ANSTO compounds (up to 1.0 mg/kg) did not show an antidepressant-like effect in the TST when given alone, however at 3.2 mg/kg, ANSTO 305 and 306 produced antidepressant-like effects. In synaptosomes, all ANSTO compounds, with the exception of analogs 303 and 306, inhibited [3H]MPP+ uptake more potently than D22. In contrast, ANSTO compounds were less potent than D22 and shifted [3H]MPP+ uptake 1- or 2 log-rightward in OCT3-HEK cells. ANSTO analogs displayed similar potencies to corticosterone, which is a blocker of OCT3. ANSTO analogs inhibited [3H]MPP+ uptake through OCT3 more favorably than PMAT (except analog 302) and OCT2 (except analogs 301 & 302). Conclusions: The significantly enhanced potency for several ANSTO compounds to inhibit [3H]MPP+ uptake in OCT3-HEK cells suggests these compounds may have higher affinity for OCT3 than PMAT or OCT2. Studies measuring behavioral outcomes and competition assays with an SSRI in WT, OCT3 knockout & PMAT knockout mice for physiological comparisons to cell overexpression systems are underway. These studies will reveal more about the pharmacological profile of these novel compounds and their potential therapeutic application to treat disorders, such as depression and drug abuse. © 2022 Springer Nature Limited
- ItemOptimization of nucleophilic 18F radiofluorinations using a microfluidic reaction approach(Nature Publishing Group, 2014-07-31) Pascali, G; Matesic, L; Collier, TL; Wyatt, NA; Fraser, BH; Pham, TQ; Salvadori, PA; Gueguric, IMicrofluidic techniques are increasingly being used to synthesize positron-emitting radiopharmaceuticals. Several reports demonstrate higher incorporation yields, with shorter reaction times and reduced amounts of reagents compared with traditional vessel-based techniques. Microfluidic techniques, therefore, have tremendous potential for allowing rapid and cost-effective optimization of new radiotracers. This protocol describes the implementation of a suitable microfluidic process to optimize classical 18F radiofluorination reactions by rationalizing the time and reagents used. Reaction optimization varies depending on the systems used, and it typically involves 5–10 experimental days of up to 4 h of sample collection and analysis. In particular, the protocol allows optimization of the key fluidic parameters in the first tier of experiments: reaction temperature, residence time and reagent ratio. Other parameters, such as solvent, activating agent and precursor concentration need to be stated before the experimental runs. Once the optimal set of parameters is found, repeatability and scalability are also tested in the second tier of experiments. This protocol allows the standardization of a microfluidic methodology that could be applied in any radiochemistry laboratory, in order to enable rapid and efficient radiosynthesis of new and existing [18F]-radiotracers. Here we show how this method can be applied to the radiofluorination optimization of [18F]-MEL050, a melanoma tumor imaging agent. This approach, if integrated into a good manufacturing practice (GMP) framework, could result in the reduction of materials and the time required to bring new radiotracers toward preclinical and clinical applications. © 2014, Nature Publishing Group
- ItemPrenatal poly I:C age-dependently alters cannabinoid type 1 receptors in offspring: a longitudinal small animal PET study using [18F]MK-9470(Elsevier, 2014-05-10) Verdurand, M; Dalton, VS; Nguyen, VH; Grégoire, MC; Zahra, D; Wyatt, NA; Burgess, L; Greguric, ID; Zavitsanou, KEvidence suggests that there is a link between the endocannabinoid system (ECS) and neuropsychiatric illnesses, including schizophrenia. Whilst the ECS has been shown to be involved in immune system regulation in various ways, it is known that infections during pregnancy can modulate the immune system of the mother and increase the risk for schizophrenia in offspring. In animal studies, maternal immune activation following administration of viral or bacterial mimics has been shown to reproduce many key structural, behavioural, and pharmacological abnormalities in offspring that resemble schizophrenia. In the present study, we used Positron Emission Tomography (PET) and [18F]MK-9470, a selective high-affinity inverse agonist radioligand for cannabinoid type 1 receptors (CB1R), to longitudinally assess CB1R expression in the progeny of female rats exposed to the viral mimic polyriboinosinic–polyribocytidilic acid (poly I:C) (4 mg/kg i.v.) or vehicle at gestational day 15 (GD 15). PET scans were performed in offspring at postnatal days (PND) 32–42 (adolescence) and in the same animals again at PNDs 75–79 (adulthood). Sixteen regions of interest were assessed, encompassing the whole rat brain. At adolescence, offspring exposed prenatally to poly I:C had significantly lower CB1R relative Standard Uptake Values (rSUV) compared to controls in the globus pallidus (p = 0.046). In adulthood, however, poly I:C exposed offspring had higher levels of CB1R rSUV in sensory cortex (p = 0.034) and hypothalamus (p = 0.032) compared to controls. Our results suggest that prenatal poly I:C leads to long term alterations in the integrity of the ECS that are age and region-specific. The increased CB1R expression in adulthood following poly I:C mirrors the increased CB1R observed in patients with schizophrenia in post-mortem and in vivo PET studies. © Elsevier
- ItemRadiosynthesis of a novel PET fluoronicotinamide for melanoma tumour PET imaging [18F]MEL050(CSIRO Publishing, 2011-01-01) Greguric, ID; Taylor, S; Pham, TQ; Wyatt, NA; Jiang, CD; Bourdier, T; Loc'h, C; Roselt, P; Neels, OC; Katsifis, A[18F]6-Fluoro-N-[2-(diethylamino)ethyl]nicotinamide [18F]MEL050 is a novel nicotinamide-based radiotracer, designed to target random metastatic dissemination of melanoma tumours by targeting melanin. Preclinical studies suggest that [18F]MEL050 has an excellent potential to improve diagnosis and staging of melanoma. Here we report the radiochemical optimization conditions of [18F]MEL050 and its large scale automated synthesis using a GE FXFN automated radiosynthesis module for clinical, phase-1 investigation. [18F]MEL050 was prepared via a one-step synthesis using no-carrier added K[18F]F-Krytpofix® 222 (DMSO, 170°C, 5 min) followed by HPLC purification. Using 6-chloro-N-[2-(diethylamino)ethyl]nicotinamide as precursor, [18F]MEL050 was obtained in 40–46% radiochemical yield (non-decay corrected), in greater than 99.9% radiochemical purity and specific activity ranging from 240 to 325 GBq μmol–1. Total synthesis time including formulation was 40 min and [18F]MEL050 was stable (99.8%) in PBS for 6 h. © 2011, CSIRO Publishing
- ItemSP-103 - Scandium-47 and lutetium-177 radiolabelling and stability studies of 1st and 2nd generation DOTA-triphenylphosphonium ligands – potential radionuclide theranostics for treatment of glioblastoma multi-forme(Elsevier, 2021-05-17) Wyatt, NA; Hogan, L; Pellegrini, PA; Roberts, MP; Hall, A; Smith, N; Hemzal, E; Hill, L; Howell, NR; Middleton, RJ; Safavi-Naeini, M; Rendina, LM; Fraser, BHScandium-47 has emerged as a promising radioisotope for targeted radionuclide tumor therapy. This is due, to a significant extent, from the combination of low energy / short range β- emission, the availability of a “perfect theranostic pair” with Sc-44 for companion PET imaging, the potential to form highly stable radiometal complexes, and the availability of suitable γ emissions for companion SPECT imaging. Sc-47 also has a shorter half-life (3.35 d) than the chemically similar Lu-177 (6.7 d) which is significant given recent in vitro research that suggests longer lived isotopes require more initial radioactivity to have the same effect upon cell viability [3]. The shorter half-life of Sc-47 also suggests it may be more suitable for smaller biological vectors (with shorter biological half-lives) such as small molecules and low MW peptides. One area of clinical treatment where Sc-47 can have impact and where improvements in patient outcomes and survival rates remain stubbornly low is glioblastoma multiforme (GBM). GBM is the most common and aggressive form of malignant brain tumor and represents around 60% of all adult brain tumors with a global incidence of <10 per 100,000 persons. The prognosis for GBM patients is poor with a -ear survival rate of 37%, 5 year rate of 5% and a median survival time of 10 months. The current standard of treatment is resection of the tumor followed by radiation therapy and chemotherapy. Given this poor prognosis there is a clear and unmet need for improved classes of treatment. Although significant progress has been made towards bringing GBM targeted radionuclide therapies to the clinic, the efforts to date have not included utilizing Sc-44/ Sc-47. Given this we are developing and evaluating Sc-44/Sc-47 and Lu-177/Ga-68 radiolabelled triphenylphosphonium (TPP) functionalised DOTA ligands (1st and 2nd generation) as potential theranostics for GBM. Described herein is our work on comparing the radiolabelling efficiency (Sc-47 vs. Lu-177) and stability studies (PBS pH 7.4, rat plasma) for our 1st and 2nd generation DOTA-TPP ligands. The presence of an additional carbonyl group in the 2nd generation DOTATPP ligand was anticipated to increase the number of donor atoms around the radiometal and affect radiolabelling reaction conditions and, more importantly, increase radiometal complex stability. Copyright © 2021 Elsevier Inc.
- ItemSynthesis and in vivo evaluation of [123I]melanin-targeted agents(American Chemical Society, 2015-08-15) Roberts, MP; Nguyen, VH; Ashford, ME; Berghofer, PJ; Wyatt, NA; Krause-Heuer, AM; Pham, TQ; Taylor, SR; Hogan, L; Jiang, CD; Fraser, BH; Lengkeek, NA; Matesic, L; Grégoire, MC; Denoyer, D; Hicks, RJ; Katsifis, A; Greguric, IDThis study reports the synthesis, [123I]radiolabeling, and biological profile of a new series of iodinated compounds for potential translation to the corresponding [131I]radiolabeled compounds for radionuclide therapy of melanoma. Radiolabeling was achieved via standard electrophilic iododestannylation in 60–90% radiochemical yield. Preliminary SPECT imaging demonstrated high and distinct tumor uptake of all compounds, as well as high tumor-to-background ratios compared to the literature compound [123I]4 (ICF01012). The most favorable compounds ([123I]20, [123I]23, [123I]41, and [123I]53) were selected for further biological investigation. Biodistribution studies indicated that all four compounds bound to melanin containing tissue with low in vivo deiodination; [123I]20 and [123I]53 in particular displayed high and prolonged tumor uptake (13% ID/g at 48 h). [123I]53 had the most favorable overall profile of the cumulative uptake over time of radiosensitive organs. Metabolite analysis of the four radiotracers found [123I]41 and [123I]53 to be the most favorable, displaying high and prolonged amounts of intact tracer in melanin containing tissues, suggesting melanin specific binding. Results herein suggest that compound [123I]53 displays favorable in vivo pharmacokinetics and stability and hence is an ideal candidate to proceed with further preclinical [131I] therapeutic evaluation. ©2015, American Chemical Society
- ItemSynthesis and pharmacological evaluation of [ 18 F]PBR316: a novel PET ligand targeting the translocator protein 18 kDa (TSPO) with low binding sensitivity to human single nucleotide polymorphism rs6971(Royal Society of Chemistry (RSC), 2021-04-01) Mattner, F; Katsifis, A; Bourdier, T; Loc'h, C; Berghofer, PJ; Fookes, CJR; Hung, TT; Jackson, TW; Henderson, D; Pham, TQ; Lee, BJ; Shepherd, R; Greguric, ID; Wyatt, NA; Le, T; Poon, J; Power, C; Fulham, MJRadiopharmaceuticals that target the translocator protein 18 kDa (TSPO) have been investigated with positron emission tomography (PET) to study neuroinflammation, neurodegeneration and cancer. We have developed the novel, achiral, 2-phenylimidazo[1,2-a]pyridine, PBR316 that targets the translocator protein 18 kDa (TSPO) that addresses some of the limitations inherent in current TSPO ligands; namely specificity in binding, blood brain barrier permeability, metabolism and insensitivity to TSPO binding in subjects as a result of rs6971 polymorphism. PBR316 has high nanomolar affinity (4.7–6.0 nM) for the TSPO, >5000 nM for the central benzodiazepine receptor (CBR) and low sensitivity to rs6971 polymorphism with a low affinity binders (LABs) to high affinity binders (HABs) ratio of 1.5. [18F]PBR316 was prepared in 20 ± 5% radiochemical yield, >99% radiochemical purity and a molar activity of 160–400 GBq μmol−1. Biodistribution in rats showed high uptake of [18F]PBR316 in organs known to express TSPO such as heart (3.9%) and adrenal glands (7.5% ID per g) at 1 h. [18F]PBR316 entered the brain and accumulated in TSPO-expressing regions with an olfactory bulb to brain ratio of 3 at 15 min and 7 at 4 h. Radioactivity was blocked by PK11195 and Ro 5-4864 but not Flumazenil. Metabolite analysis showed that radioactivity in adrenal glands and the brain was predominantly due to the intact radiotracer. PET–CT studies in mouse-bearing prostate tumour xenografts indicated biodistribution similar to rats with radioactivity in the tumour increasing with time. [18F]PBR316 shows in vitro binding that is insensitive to human polymorphism and has specific and selective in vivo binding to the TSPO. [18F]PBR316 is suitable for further biological and clinical studies. © Royal Society of Chemistry 2025.
- ItemSynthesis and radiosynthesis of a novel PET fluorobenzyl piperazine for melanoma tumour imaging; [18F]MEL054(CSIRO publishing, 2012-02-18) Taylor, SR; Roberts, MR; Wyatt, NA; Pham, TQ; Stark, D; Bourdier, T; Roselt, P; Katsifis, A; Greguric, ID2-{2-[4-(4-[18F]-Fluorobenzyl)piperazin-1-yl]-2-oxoethyl}isoindolin-1-one ([18F]MEL054), is a new potent indolinone-based melanin binder designed to target melanotic tumours. [18F]MEL054 was prepared by an automated two-step radiosynthesis, comprising of the preparation of 4-[18F]fluorobenzaldehyde from 4-formyl-N,N,N-trimethylanilinium triflate, followed by reductive alkylation with 2-(2-oxo-2-piperazin-1-ylethyl)isoindolin-1-one. 4-[18F]Fluorobenzaldehyde was prepared on a GE TRACERlab FXFN module in 68 ± 8 % radiochemical yield (RCY, non-decay corrected), purified by a Sep-Pak Plus C18 cartridge and eluted into the reactor of an in-house modified Nuclear Interface [18F]FDG synthesis module for the subsequent reductive alkylation reaction. HPLC purification produced [18F]MEL054 in a collected RCY of 34 ± 9 % (non-decay corrected), the total preparation time (including Sep-Pak Plus C18 and HPLC purification) did not exceed 105 min. The radiochemical purity of [18F]MEL054 was greater than 99 % with a specific radioactivity of 71–119 GBq μmol–1 and [18F]MEL054 remained stable in saline solution (>98 %) after 3 h. © 2013 CSIRO.
- ItemSynthesis, bioconjugation and stability studies of [18F]ethenesulfonyl fluoride(John Wiley & Sons, Inc, 2018-06-20) Zhang, B; Pascali, G; Wyatt, NA; Matesic, L; Klenner, MA; Sia, TR; Guastella, AJ; Massi, M; Robinson, AJ; Fraser, BHFluorine-18 labelled prosthetic groups (PGs) are often necessary for radiolabelling sensitive biological molecules such as peptides and proteins. Several shortcomings, however, often diminish the final yield of radiotracer. In an attempt to provide higher yielding and operationally efficient tools for radiolabelling biological molecules, we describe herein the first radiochemical synthesis of [18F]ethenesulfonyl fluoride ([18F]ESF) and its Michael conjugation with amino acids and proteins. The synthesis of [18F]ESF was optimised using a microfluidic reactor under both carrier-added (c.a.) and no-carrier-added (n.c.a.) conditions, affording, in a straightforward procedure, 30-50% radiochemical yield (RCY) for c.a. [18F]ESF and 60-70% RCY for n.c.a. [18F]ESF. The conjugation reactions were performed at room temperature using 10 mg/mL precursor in aqueous/organic solvent mixtures for 15 min. The radiochemical stability of the final conjugates was evaluated in injectable formulation and rat serum, and resulted strongly substrate dependent and generally poor in rat serum. Therefore, in this work we have optimised a straightforward synthesis of [18F]ESF and its Michael conjugation with model compounds, without requiring chromatographic purification. However, given the general low stability of the final products, further studies will be required for improving conjugate stability, before assessing the use of this PG for PET imaging. © 2018 John Wiley & Sons, Inc.
- ItemTo D or not to D – an in vitro/mass spectrometry screening method to confirm improved metabolic stability in deuterium-labelled radiotracers(Australian Nuclear Science and Technology Organisation, 2019-09-03) Murphy, RB; Wyatt, NA; Fraser, BH; Yepuri, NR; Holden, PJ; Wotherspoon, ATL; Darwish, TADeuteration, where hydrogen within molecules is switched with the non-radioactive and naturally occurring isotope deuterium, can lead to enhanced material properties. For example, the deuterium kinetic isotope effect is well known to improve the metabolic stability of molecules such as drugs, as the C–D bond is stronger and more difficult for enzymes to break than the C–H bond. However, the specific molecular location to deuterate to gain a metabolically favourable outcome may not be clear, without undertaking separate assays of both the deuterated and non-deuterated molecules, followed by separate HPLC-UV/radiometric measurement. In the case of compounds which also contain a radiolabel (e.g. radiotracers for diagnostic medical imaging), specialist infrastructure and teams are required, and chemical synthesis and bioanalysis are time-critical. Our ongoing work with the radiotracer [18F]PBR111, a TSPO ligand showing potential for imaging neuroinflammation1,2,3, demonstrated that [18F]PBR111-d4 (where d4 is incorporated at a specific site) has slower metabolic breakdown4,5 and a decreased rate of formation of polar metabolites in vitro (rat and human liver microsomes) relative to non-deuterated 5,6. Our recently published MS/MS method4 demonstrates the relative difference in metabolic stability without radiolabelling, by analysing different time points from a liver microsome assay which has been administered a 50:50 mixture of deuterated/non-deuterated compound. Pharmacokinetic parameters can also be determined from the data. Deuteration adjacent to the fluoro-alkyl group in PBR111 showed ~50% improvement in the stability of the intact radiotracer relative to non-deuterated using a ratio determination of the analogous MS transitions unique to the deuterated/non-deuterated compounds4. As a control, a second deuterated analogue was also synthesised4 with deuterium purposely incorporated at a site significantly less metabolised than the first site5, which our newly developed method was also able to confirm. We expect this simple and rapid method could be applied to deuterated and non-deuterated analogues of other biologically important molecules to determine the suitability of the chosen site of deuteration. For radiotracers, there is no requirement to radiolabel until studies progress to in vivo PET imaging.