Brain Uptake Research Articles

Dual PET imaging of microtubules and synaptic density in a mouse model of Alzheimer’s Disease

AbstractBackgroundWhile microtubule (MT)‐destabilization and synaptic loss hallmark AD pathological events, no study has systematically quantified their in vivo levels in the same brain. Any therapeutic intervention relying on MT destabilization and synaptic vesicle protein (SV2A) levels will benefit from a dual PET imaging strategy, providing target engagement, dosing, and occupancy studies for new drugs. Here, we report MT destabilization and synaptic density imaging results using [11C]MPC‐6827 and [18F]UCB‐H respectively in the same transgenic (TG) and wild‐type (WT) APP/PS1 mice.MethodMale APP/PS1 TG and WT mice (12‐14 mo, 20± 2g, n = 8/group) underwent 30‐min dynamic brain microPET/CT imaging with [11C]MPC‐6827 (0.2±0.02 mCi, iv tail). Four hours later, the same animals underwent another 30‐min brain PET/CT with [18F]UCB‐H (0.2±0.01 mCi, iv tail). A sub‐set of TG and WT mice (n = 4/group) were used to measure ex vivo destabilized MTs and SV2A levels using western blot to confirm MT destabilization and synaptic loss. Whole‐brain standard uptake values (SUVs) were calculated from co‐registered PET‐CT using PMOD. Ex vivo post‐PET biodistribution studies were performed, with percent injected dose‐pe‐ gram (%ID/g) calculated. 48h post‐biodistribution, in vitro autoradiography studies were performed on frozen brain samples from the same animals with [11C]MPC‐6827 and [18F]UCBH; regional uptake was quantified using phosphor‐stimulated luminescence.Result[11C]MPC‐6827 and [18F]UCBH were produced in high (>97±2%) radiochemical purities (n = 20 productions) and specific activities (∼3980±100 mCi/µmol), decay‐corrected to end‐of‐synthesis. Western blot analysis confirmed high destabilized MTs, and low SV2A levels in TG vs. WT. SUV analysis (Fig. 1) showed 56% higher [11C]MPC‐6827 and 66% lower [18F]UCB‐H in vivo brain uptake in TG compared to WT (**p = 0.0032). %ID/g analysis showed 58% higher [11C]MPC‐6827 and 61% lower [18F]UCB‐H ex vivo brain radioactive uptake in TG vs WT (*p = 0.04). Importantly, autoradiography demonstrated 44% higher [11C]MPC‐6827 and 34% lower [18F]UCB‐H in vitro uptake in cortical and hippocampal regions of TG vs. WT (*p = 0.05).ConclusionTG APP/PS1 mice demonstrated higher [11C]MPC‐6827 and lower [18F]UCB‐H brain uptake compared to WT littermates. In vivo PET, ex vivo biodistribution, and in vitro autoradiography data corroborated each other. Preliminary [11C]MPC‐6827 and [18F]UCB‐H PET evaluations showed negative correlations (*r = ‐0.778), suggesting MT destabilization and synaptic loss happen concurrently.

Dual PET imaging of microtubules and synaptic density in a mouse model of Alzheimer’s Disease

AbstractBackgroundWhile microtubule (MT)‐destabilization and synaptic loss hallmark AD pathological events, no study has systematically quantified their in vivo levels in the same brain. Any therapeutic intervention relying on MT destabilization and synaptic vesicle protein (SV2A) levels will benefit from a dual PET imaging strategy, providing target engagement, dosing, and occupancy studies for new drugs. Here, we report MT destabilization and synaptic density imaging results using [11C]MPC‐6827 and [18F]UCB‐H respectively in the same transgenic (TG) and wild‐type (WT) APP/PS1 mice.MethodMale APP/PS1 TG and WT mice (12‐14 mo, 20± 2g, n = 8/group) underwent 30‐min dynamic brain microPET/CT imaging with [11C]MPC‐6827 (0.2±0.02 mCi, iv tail). Four hours later, the same animals underwent another 30‐min brain PET/CT with [18F]UCB‐H (0.2±0.01 mCi, iv tail). A sub‐set of TG and WT mice (n = 4/group) were used to measure ex vivo destabilized MTs and SV2A levels using western blot to confirm MT destabilization and synaptic loss. Whole‐brain standard uptake values (SUVs) were calculated from co‐registered PET‐CT using PMOD. Ex vivo post‐PET biodistribution studies were performed, with percent injected dose‐pe‐ gram (%ID/g) calculated. 48h post‐biodistribution, in vitro autoradiography studies were performed on frozen brain samples from the same animals with [11C]MPC‐6827 and [18F]UCBH; regional uptake was quantified using phosphor‐stimulated luminescence.Result[11C]MPC‐6827 and [18F]UCBH were produced in high (>97±2%) radiochemical purities (n = 20 productions) and specific activities (∼3980±100 mCi/µmol), decay‐corrected to end‐of‐synthesis. Western blot analysis confirmed high destabilized MTs, and low SV2A levels in TG vs. WT. SUV analysis (Fig. 1) showed 56% higher [11C]MPC‐6827 and 66% lower [18F]UCB‐H in vivo brain uptake in TG compared to WT (**p = 0.0032). %ID/g analysis showed 58% higher [11C]MPC‐6827 and 61% lower [18F]UCB‐H ex vivo brain radioactive uptake in TG vs WT (*p = 0.04). Importantly, autoradiography demonstrated 44% higher [11C]MPC‐6827 and 34% lower [18F]UCB‐H in vitro uptake in cortical and hippocampal regions of TG vs. WT (*p = 0.05).ConclusionTG APP/PS1 mice demonstrated higher [11C]MPC‐6827 and lower [18F]UCB‐H brain uptake compared to WT littermates. In vivo PET, ex vivo biodistribution, and in vitro autoradiography data corroborated each other. Preliminary [11C]MPC‐6827 and [18F]UCB‐H PET evaluations showed negative correlations (*r = ‐0.778), suggesting MT destabilization and synaptic loss happen concurrently.

Discovery and optimization of the first‐in‐class TDP‐43 PET tracer

AbstractBackgroundIntracellular aggregation of TDP‐43 is found in most patients with amyotrophic lateral sclerosis (ALS), 45% of patients with frontotemporal dementia (FTD) and 30‐50% of patients with clinical diagnosis of Alzheimer’s disease. Sensitive fluid or imaging biomarkers of TDP‐43 pathology are currently not available. Direct detection of TDP‐43 aggregates by positron emission tomography (PET) holds promise for a more accurate diagnosis, patient stratification and assessment of therapeutic efficacy in clinical trials.MethodsUsing ACI’s Morphomer® small molecule library focused on brain penetrant and beta sheet binding compounds, initial hits were identified, and iterative medicinal chemistry applied to discover compounds with optimized properties. Radiobinding and autoradiography experiments on FTLD‐TDP brain samples were used to evaluate affinity and target engagement. These techniques were also used to assess selectivity over other aggregation‐prone proteins using brain material from Alzheimer’s (AD) and Parkinson’s disease (PD) cases. Brain pharmacokinetic (PK) profile was obtained in mice, followed by assessment of brain uptake, distribution and washout for selected 18F radiolabeled compounds in non‐human primates (NHP).ResultsSeveral chemical series showing nanomolar binding affinity to aggregated TDP‐43 from patient brain samples were identified. The specificity of binding was further confirmed by high resolution autoradiography enabling visualization of target engagement on TDP‐43 inclusions in FTLD‐TDP brain sections. In addition, the most advanced compounds differentiated FTLD‐TDP from control by classical autoradiography on patient brain sections. Selectivity over amyloid beta, alpha‐synuclein and Tau was observed. The compounds with the most favorable brain penetrantion properties demonstrated fast and substantial brain uptake and fast and complete washout in NHPs.ConclusionsFirst‐in‐class TDP‐43 PET ligands have been discovered with the potential to identify FTLD‐TDP pathology by PET. These tools may finally allow the ability to detect and follow the progression of TDP‐43 pathology in the brains of living patients with certain TDP‐43 proteinopathies.

Personalized nutritional ketosis through a whole‐food low‐carb diet, medium chain triglycerides, and other ketogenic strategies for people with mild cognitive impairment and Alzheimer’s disease

AbstractInsulin resistance with abnormal brain glucose uptake, a brain‐energy gap, and neuroinflammation are common in the aging brain and are exaggerated in people with Alzheimer’s disease (AD) and in some people with MCI (Cunnane Nature Reviews Drug Discovery 2020). Ketones are an alternative fuel for the brain and ketone uptake is normal in brain regions affected by abnormal glucose uptake in AD (Castellano J Alzheim Dis 2015). Ketones are anti‐inflammatory (Kim Frontiers Immunol 2022) and lessen beta amyloid plaques, tau tangles, and anxiety in animal models (Kashiwaya PNAS 2000; Wu FASEB 2020). Increased brain energy from ketones has been demonstrated using PET imaging in clinical trials of MCT oil (Fortier Alz Dementia 2021), ketogenic diet (KD) (Neth Neurobiol Aging 2020), and exercise (Vandenberghe Appl Physiol Nutr Metab 2019). Recent studies report cognitive and/or other clinical improvements in MCI and/or AD with KD (Brandt J Alzheimers Dis 2019), modified Mediterranean KD (Neth Neurobiol Aging 2020), KD with MCT oil (Taylor Alzheimers Dement 2017), KD with coconut oil in keto study diet recipes (Phillips Alz Research & Therapy 2021), MCT oil with habitual diet (Reger Neurobio Ageing 2004; Constantini Nutri Metab 2009; Maynard Neuropsych Disease Treat 2013; Abe J Nutr Sci Vitaminol 2017; Abe J Nutr 2016; Xu et al. Clin Nutr 2020; Fortier Alz & Dementia 2021), and coconut oil with habitual diet (De la Rubia Orti Nutr Hosp 2017). Case reports of people with AD consuming KD, MCTs, and/or ketone ester also report cognitive improvement (Maynard Neuropsych Disease Treat 2013; Newport Alz Dementia 2015; Stoykovich Alz Dementia 2019; Morrill Diab Metab Syndr:Clin Res & Rev 2019). Ketone esters can rapidly and substantially increase blood ketone levels. Given the lack of any FDA‐approved drug that results in meaningful improvement for people with AD, accumulating evidence suggests that adopting a personalized program for people with AD, aiming for mild to moderate ketosis (blood betahydroxybutyrate levels 0.5‐2 mmol/L), could provide a safe and reasonable therapeutic approach to improve cognitive impairment and other symptoms and could offer a strategy to delay or prevent AD in persons at risk.

Development of Novel COX-2 Imaging Agents for the Diagnosis of Brain Lesions

Cyclooxygenase-2 (COX-2) has attracted attention as a biomarker for neurodegenerative brain diseases. The aim of this study was to develop a COX-2 imaging agent for positron emission tomography (PET) that binds to and emits radiation from COX-2 in the central nervous system to diagnose brain lesions related to COX-2. To this end, the development of PET imaging probes by derivatizing non-steroidal anti-inflammatory drugs that bind to COX-2 was investigated. Herein, we present the findings of a series of studies on indomethacin and nimesulide derivatives. All five 11C-labeled indomethacin derivatives showed low brain uptake and were rapidly metabolized in vivo, indicating that they are inadequate COX-2 imaging agents. However, the evaluation of 11C-labeled indomethacin derivatives revealed an inverse relationship between the amount taken up by the brain and the lipophilicity of the compound, and that P-glycoprotein (P-gp) may be responsible for the low brain uptake of 11C-labeled indomethacin derivatives. To overcome the problems associated with 11C-labeled indomethacin derivatives, nimesulide was selected as a novel COX-2 imaging agent. Although the nimesulide derivatives were less lipophilic and unaffected by P-gp, all three 11C-labeled nimesulide derivatives showed low brain uptake and were rapidly metabolized. However, the 11C-labeled nimesulide derivatives were partially useful as brain-targeted COX-2 imaging agents because they bound specifically to COX-2 in the brain of mice and successfully imaged the regional brain distribution associated with COX-2. In the development of COX-2 imaging agents, in vivo stability of the compounds is a future objective.

Personalized Nutrition for APOE4 carriers: mechanisms and biomarkers that can inform future trials

AbstractCurrent studies suggest that the beneficial effects of increased polyunsaturated fat consumption (Mediterranean diet, fish consumption or long‐term DHA supplementation) on cognition are stronger in younger and middle aged APOE4 carriers. The efficacy of these nutritional interventions in APOE4 appears to wane with advancing age and cognitive disease. In addition, a recent systematic review revealed that ketogenic diets do not appear to have a beneficial effect on cognitive performance in APOE4 carriers compared to non‐carriers.In this talk, we focus on leading mechanisms of cerebral bioenergetic breakdown in the aging APOE4 brain that implicate neuroinflammation in several brain cell types including those of the blood‐brain barrier (BBB). We then address consequences of neuroinflammation and disturbed bioenergetics at the BBB on the delivery and brain metabolism of nutrients such as omega‐3s, nutrients and ketones. We provide examples of novel lipidomic biomarkers that can capture neuroinflammation in the Religious Order Study, DHA Brain Pilot Trial, and the ADCS DHA trial. Advances in brain imaging of polyunsaturated fatty acid brain uptake by PET are provided to obtain insights into APOE4 brain fatty acid consumption changes during the lifespan. Finally, we highlight how the ongoing PreventE4 trial is integrating measures of the gut microbiome to understand the effects of omega‐3 supplementation on the brain in individuals carrying the APOE4 allele and at risk for dementia.

18F]MK6240 and [18F]PI2620 autoradiography on postmortem human brain tissue in AD

AbstractBackgroundTo compare the post mortem uptake of [18F]MK6240 and [18F]PI2620 in the brain hemisphere, of A‐T‐ (CN) and A+T+ tissueMethodAutoradiography (ARG) imaging using [18F]MK6240 and [18F]PI2620 was used to assess uptake of CN and AD tissues. One study used sections of whole‐hemisphere of one CN tissue and one AD tissue. The uptake value of [18F]MK6240 was calculated from a regions of interest (ROI) drawn manually from the area of cortex gray matter (GM), cortex white matter (WM), and background (BG).Other study was 24 tissues from the prefrontal cortex (Pfc) (12CN, 12AD), hippocampus (Hip) (12 CN, 12 AD) and cerebellum (Cer) (12 CN, 12 AD) were evaluated with [18F]MK6240, and [18F]PI2620. The uptake value of [18F]MK6240 and [18F]PI2620 was calculated from ROI drawn manually from the area of pfc GM, hip GM and cer GM.ResultThe ARG showed greater [18F]MK6240 uptake in AD than in CN tissue. There were significant differences between CN and AD tissue in terms of cortex gray GM distribution and cortex WM, but no significant differences in BG. These results also, there is no correlation between the specific activity of [18F]MK6240 and the uptake value in CN and AD tissues. In a second experiment, based on our findings there was a significant difference between CN and AD groups when assessed by [18F]MK6240 as well as [18F]PI2620 in the pfc_GM and hip_GM. Furthermore, we found no difference between AD and CN tissues when assessed by [18F]MK6240 and [18F]PI2620 in cerebellum GM. Ratio values Pfc/Cer and Hip/Cer assessed by [18F]MK6240 as well as there were significant differences between CN and AD. [18F]MK6240 and [18F]PI2620 were highly correlated in AD but not in CN brain tissues.ConclusionWe also found that [18F]PI2620 and [18F]MK6240 have similar brain uptake in post‐mortem tissue.

PET Imaging of Innate Immune Activation Using 11C Radiotracers Targeting GPR84.

Chronic innate immune activation is a key hallmark of many neurological diseases and is known to result in the upregulation of GPR84 in myeloid cells (macrophages, microglia, and monocytes). As such, GPR84 can potentially serve as a sensor of proinflammatory innate immune responses. To assess the utility of GPR84 as an imaging biomarker, we synthesized 11C-MGX-10S and 11C-MGX-11Svia carbon-11 alkylation for use as positron emission tomography (PET) tracers targeting this receptor. In vitro experiments demonstrated significantly higher binding of both radiotracers to hGPR84-HEK293 cells than that of parental control HEK293 cells. Co-incubation with the GPR84 antagonist GLPG1205 reduced the binding of both radiotracers by >90%, demonstrating their high specificity for GPR84 in vitro. In vivo assessment of each radiotracer via PET imaging of healthy mice illustrated the superior brain uptake and pharmacokinetics of 11C-MGX-10S compared to 11C-MGX-11S. Subsequent use of 11C-MGX-10S to image a well-established mouse model of systemic and neuro-inflammation revealed a high PET signal in affected tissues, including the brain, liver, lung, and spleen. In vivo specificity of 11C-MGX-10S for GPR84 was confirmed by the administration of GLPG1205 followed by radiotracer injection. When compared with 11C-DPA-713-an existing radiotracer used to image innate immune activation in clinical research studies-11C-MGX-10S has multiple advantages, including its higher binding signal in inflamed tissues in the CNS and periphery and low background signal in healthy saline-treated subjects. The pronounced uptake of 11C-MGX-10S during inflammation, its high specificity for GPR84, and suitable pharmacokinetics strongly support further investigation of 11C-MGX-10S for imaging GPR84-positive myeloid cells associated with innate immune activation in animal models of inflammatory diseases and human neuropathology.

99mTc(CO)3-labeled 1-(2-Pyridyl)piperazine derivatives as radioligands for 5-HT7 receptors.

The 5-hydroxytryptamine receptor (5-HTR) family includes seven classes of receptors. The 5-HT7R is the newest member of this family and contributes to different physiological and pathological processes. As a pathology, glioblastoma multiform (GBM) overexpresses 5-HT7R; hence, this study aims to develop radiolabeled aryl piperazine derivatives as 5-HT7R imaging agents. METHODS: Compounds 6 and 7 as 1-(3-nitropyridin-2-yl)piperazine derivatives were radiolabeled with fac-[99mTc(CO)3(H2O)3]+ and 99mTc(CO)3-[6] and 99mTc(CO)3-[7] were obtained with high radiochemical purity (RCP > 94%).The stability of the radiotracers was evaluated in both saline and mouse serum. Specific binding on different cell lines including U-87 MG, MCF-7, SKBR3, and HT-29 was performed. The biodistribution of these radiotracers was evaluated in normal and U-87 MG Xenografted models. Finally, 99mTc(CO)3-[6] and 99mTc(CO)3-[7] were applied for in vivo imaging in U-87 MG Xenografted models. Specific binding study indicates that 99mTc(CO)3-[6] and 99mTc(CO)3-[7] can recognize 5-HT7R of U87-MG cell line. The biodistribution study in normal mice indicates that the brain uptake of 99mTc(CO)3-[6] and 99mTc(CO)3-[7] is the highest at 30min post-injection (0.8 ± 0.25 and 0.64 ± 0.18%ID/g, respectively). The data of the biodistribution study in the U87-MG xenograft model revealed that these radiotracers could accumulate in the tumor site, and the highest tumor uptake was observed at 60min post-injection (3.38 ± 0.65 and 3.27 ± 0.5%ID/g, respectively). The injection of pimozide can block the tumor's radiotracer uptake, indicating the binding of these radiotracers to the 5-HT7R. The imaging study in the xenograft model also confirms the biodistribution data. The acquired images clearly show the tumor site, and the tumor-to-muscle ratio for 99mTc(CO)3-[6] and 99mTc(CO)3-[7] at 60min was 3.33 and 3.88, respectively. CONCLUSIONS: 99mTc(CO)3-[6] and 99mTc(CO)3-[7] can visualize tumorin theU87-MG xenograft modeldueto their affinitytoward5-HT7R.

Development and Pharmacochemical Characterization Discover a Novel Brain-Permeable HDAC11-Selective Inhibitor with Therapeutic Potential by Regulating Neuroinflammation in Mice.

Recent studies have shown that the epigenetic protein histone deacetylase 11 (HDAC11) is highly expressed in the brain and critically modulates neuroimmune functions, making it a potential therapeutic target for neurological disorders. Herein, we report the development of PB94, which is a novel HDAC11 inhibitor. PB94 exhibited potency and selectivity against HDAC11 with IC50 = 108 nM and >40-fold selectivity over other HDAC isoforms. Pharmacokinetic/pharmacodynamic evaluation indicated that PB94 possesses promising drug-like properties. Additionally, PB94 was radiolabeled with carbon-11 as [11C]PB94 for positron emission tomography (PET), which revealed significant brain uptake and metabolic properties suitable for drug development in live animals. Furthermore, we demonstrated that neuropathic pain was associated with brain upregulation of HDAC11 and that pharmacological inhibition of HDAC11 by PB94 ameliorated neuropathic pain in a mouse model. Collectively, our findings support further development of PB94 as a selective HDAC11 inhibitor for neurological indications, including pain.

Altering distribution profile of palbociclib by its prodrugs

Palbociclib, a cyclin-dependent kinase (CDK) 4/6 inhibitor, is currently used clinically for treating hormone receptor-positive and human epidermal growth factor receptor 2 negative breast cancer. Additionally, it has the potential to be utilized in the treatment of various tumors, including malignant glioblastoma. Previous research has indicated that palbociclib is a substrate for two efflux transporters, P-glycoprotein (P-gp; MDR1) and breast cancer-resistant protein (BCRP), which restrict the brain exposure of palbociclib. In the present study, our objective was to alter the brain distribution pattern of palbociclib by creating and assessing two novel prodrugs through in vitro, in situ, and in vivo evaluations. To this end, we synthesized two prodrugs of palbociclib by attaching it to the tyrosine promoiety at the para- (PD1) and meta-(PD2) position via a carbamate bond. We hypothesized that the prodrugs could bypass efflux transporter-mediated drug resistance by leveraging the l-type amino acid transporter (LAT1) to facilitate their transport across the blood-brain barrier (BBB) and into cancer cells, such as glioma cells that express LAT1.The compounds PD1 and PD2 did not show selective binding and had limited inhibitory effects on LAT1 in three cell lines (MCF-7, U87-MG, HEK-hLAT1). However, PD1 and PD2 demonstrated the ability to evade efflux mechanisms, and their in vitro uptake profiles were comparable to that of palbociclib, indicating their potential for effective cellular transport. In in situ and in vivo studies, brain uptake was not significantly improved compared to palbociclib, but the pharmacokinetic profiles showed encouraging enhancements. PD1 exhibited a higher AUCbrain/plasma ratio, suggesting safer dosing, while PD2 showed favorable long-acting pharmacokinetics.Although our prodrug design did not significantly improve palbociclib brain delivery due to the potential size limitation of the prodrugs, the study provides valuable insights for future prodrug development and drug delivery strategies targeting specific transporters.

Evaluation of trans- and cis-4-[18F]Fluorogabapentin for Brain PET Imaging.

Gabapentin, a selective ligand for the α2δ subunit of voltage-dependent calcium channels, is an anticonvulsant medication used in the treatment of neuropathic pain, epilepsy, and other neurological conditions. We recently described two radiofluorinated derivatives of gabapentin (trans-4-[18F]fluorogabapentin, [18F]tGBP4F, and cis-4-[18F]fluorogabapentin, [18F]cGBP4F) and showed that these compounds accumulate in the injured nerves in a rodent model of neuropathic pain. Given the use of gabapentin in brain diseases, here we investigate whether these radiofluorinated derivatives of gabapentin can be used for imaging α2δ receptors in the brain. Specifically, we developed automated radiosynthesis methods for [18F]tGBP4F and [18F]cGBP4F and conducted dynamic PET imaging in adult rhesus macaques with and without preadministration of pharmacological doses of gabapentin. Both radiotracers showed very high metabolic stability, negligible plasma protein binding, and slow accumulation in the brain. [18F]tGBP4F, the isomer with higher binding affinity, showed low brain uptake and could not be displaced, whereas [18F]cGBP4F showed moderate brain uptake and could be partially displaced. Kinetic modeling of brain regional time-activity curves using a metabolite-corrected arterial input function shows that a one-tissue compartment model accurately fits the data. Graphical analysis using Logan or multilinear analysis 1 produced similar results as compartmental modeling, indicating robust quantification. This study advances our understanding of how gabapentinoids work and provides an important advancement toward imaging α2δ receptors in the brain.

Intranasal delivery of poly (d-glucosamine) encrusted self-assembled lipidic nanovesicles to enhanced brain uptake of thymoquinone for management of Glioblastoma Multiforme

Glioblastoma Multiforme (GBM) is a grade IV primary malignant brain tumour, which is highly infiltrative and exhibits a poor prognosis which results in high mortality. Low solubility and stability are the major hurdles faced while developing drug delivery systems for the treatment of GBM. Therefore, this study focuses on the enhancement of brain uptake of thymoquinone (TH) by formulating poly (d-glucosamine) self-assembled lipidic nanovesicles for intranasal delivery using 3-level and 3-factor central composite design (CCD). The nanovesicles were formulated using thin film hydration technique and were spherical with the particle size of 129.13 ± 2.3 nm and 32.4 ± 2.4 mV of zeta potential. The formulation exhibited high entrapment and drug loading of TH i.e., 95.07 ± 0.8 % and 8.91 ± 0.2 % respectively. The nanovesicles attained a sustained release of TH of 89.62 ± 2.9 % in 48 h with improved drug permeation of 41.89 ± 1.61 % in 12 h from nasal mucosa with enhanced mucoadhesion of 72.98 ± 1.78 %. The in-vitro cellular studies indicated the high anticancer potential of TH by lowering the cell viability to 32.90 ± 0.91 % at 25 μg/mL (IC50;21.10 μg/mL) and high radical scavenging of 69.35 ± 1.91 % (IC50;18.10 μg/mL) and improved cellular uptake of 48.71 ± 0.10ng/100 cells. Greater bioavailability of TH in CNS (∼3 folds that of IV solution) was observed along with a high drug-targeting percentage (98.1 ± 3.90 %) and drug-targeting index (11.67 ± 1.87 %) post-intranasal administration of the formulation. Quantitative uptake of the formulation was estimated using fluorescence imaging, which showed higher uptake in tissues of the brain. The formulation was having very less hemolysis (<8 %). Hence the formulated carriers can be a promising tool for the treatment of GBM.

Regional neuroinflammation induced by peripheral infection contributes to fatigue-like symptoms: a [18F]DPA-714 positron emission tomography study in rats.

A series of symptoms, including fever, widespread pain, fatigue, and even ageusia, have frequently been reported in the context of various infections, such as COVID-19. Although the pathogenic mechanisms underlying an infection causing fever and pain have been well established, the mechanisms of fatigue induced by infection in specific brain regions remain unclear. To elucidate whether and how the peripheral infection cause fatigue via regional neuroinflammation, we performed a brain-wide investigation of neuroinflammation in a peripheral pseudoinfection rat model using [18F]DPA-714 positron emission tomography (PET) imaging analysis, in which the polyriboinosinic: polyribocytidylic acid (poly I:C) was intraperitoneally injected. Transient fever lasting for several hours and subsequent suppression of spontaneous activity lasting a few days were induced by poly I:C treatment. Significant increase in plasma interleukin (IL)-1β, IL-6 and tumour necrosis factor (TNF)-α were observed at 2 and 4 h following poly I:C treatment. PET imaging analysis revealed that the brain uptake of [18F]DPA-714 was significantly increased in several brain regions one day after poly I:C treatment, such as the dorsal raphe (DR), parvicellular part of red nucleus (RPC), A5 and A7 noradrenergic nucleus, compared with the control group. The accumulation of [18F]DPA-714 in the DR, RPC and A5 was positively correlated with subsequent fatigue-like behavior, and that in the A7 tended to positively correlate with fever. These findings suggest that peripheral infection may trigger regional neuroinflammation, which may cause specific symptoms such as fatigue. A similar mechanism might be involved in COVID-19.

Evaluation of thiadiazine-based PET radioligands for imaging the AMPA receptor

As a subclass of ionotropic glutamate receptors (iGluRs), α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA) receptors have been implicated in various neurological disorders and neurodegenerative diseases. To further our understanding of AMPA receptor-related disorders in the central nervous system (CNS), it is important to be able to image and quantify AMPA receptors in vivo. In this study, we identified a novel F-containing AMPA positive allosteric modulator (PAM) 6 as a potential lead compound. Molecular docking studies and CNS PET multi-parameter optimization (MPO) analysis were used to predict the absorption, distribution, metabolism, and excretion (ADME) characteristics of 6 as a PET probe. The resulting PET probe, [18F]6 (codename [18F]AMPA-2109), was successfully radiolabeled and demonstrated excellent blood-brain barrier (BBB) permeability and high brain uptake in rodents and non-human primates. However, [18F]6 did not show substantial specific binding in the rodent or non-human primate brain. Further medicinal chemistry efforts are necessary to improve specific binding, and our work may serve as a starting point for the design of novel 18F-labeled AMPA receptor-targeted PET radioligands aimed for clinical translation.

Dimeric ferulic acid conjugate as a prodrug for brain targeting after nasal administration of loaded solid lipid microparticles

ABSTRACT Objective Ferulic acid (Fer) displays antioxidant/anti-inflammatory properties useful against neurodegenerative diseases. To increase Fer uptake and its central nervous system residence time, a dimeric prodrug, optimizing the Fer loading on nasally administrable solid lipid microparticles (SLMs), was developed. Methods The prodrug was synthesized as Fer dimeric conjugate methylated on the carboxylic moiety. Prodrug antioxidant/anti-inflammatory properties and ability to release Fer in physiologic environments were evaluated. Tristearin or stearic acid SLMs were obtained by hot emulsion technique. In vivo pharmacokinetics were quantified by HPLC. Results The prodrug was able to release Fer in physiologic environments (whole blood and brain homogenates) and induce in vitro antioxidant/anti-inflammatory effects. Its half-life in rats was 18.0 ± 1.9 min. Stearic acid SLMs, exhibiting the highest prodrug loading and dissolution rate, were selected for nasal administration to rats (1 mg/kg dose), allowing to obtain high prodrug bioavailability and prolonged residence in the cerebrospinal fluid, showing AUC (Area Under Concentration) values (108.5 ± 3.9 μg∙mL−1∙min) up to 30 times over those of Fer free drug, after its intravenous/nasal administration (3.3 ± 0.3/5.16 ± 0.20 μg∙mL−1∙min, respectively) at the same dose. Chitosan presence further improved the prodrug brain uptake. Conclusions Nasal administration of prodrug-loaded SLMs can be proposed as a noninvasive approach for neurodegenerative disease therapy.

P-074 - Identification of (R)-[18F]YH134 as a promising reversible MAGL PET tracer and the impact of peripheral MAGL blockade on its brain uptake

P-074 - Identification of (R)-[18F]YH134 as a promising reversible MAGL PET tracer and the impact of peripheral MAGL blockade on its brain uptake

O-64 - [18F]OXD-2314: A 4R-Tau PET Radiotracer with Improved Affinity and Brain Uptake

O-64 - [18F]OXD-2314: A 4R-Tau PET Radiotracer with Improved Affinity and Brain Uptake

Semiquantitative analysis of cerebral [18F]FDG-PET uptake in pediatric patients

BackgroundGlycolytic metabolism in the brain of pediatric patients, imaged with [18F] fluorodeoxyglucose-positron emission tomography (FDG-PET) is incompletely characterized.ObjectiveThe purpose of the current study was to characterize [18F]FDG-PET brain uptake in a large sample of pediatric patients with non-central nervous system diseases as an alternative to healthy subjects to evaluate changes at different pediatric ages.Materials and MethodsSeven hundred ninety-five [18F]FDG-PET examinations from children < 18 years of age without central nervous system diseases were included. Each brain image was spatially normalized, and the standardized uptake value (SUV) was obtained. The SUV and the SUV relative to different pseudo-references were explored as a function of age.ResultsAt all evaluated ages, the occipital lobe showed the highest [18F]FDG uptake (0.27 ± 0.04 SUV/year), while the parietal lobe and brainstem had the lowest uptake (0.17 ± 0.02 SUV/year, for both regions). An increase [18F]FDG uptake was found for all brain regions until 12 years old, while no significant uptake differences were found between ages 13 (SUV = 5.39) to 17 years old (SUV = 5.52) (P < 0.0001 for the whole brain). A sex dependence was found in the SUVmean for the whole brain during adolescence (SUV 5.04–5.25 for males, 5.68–5.74 for females, P = 0.0264). Asymmetries in [18F]FDG uptake were found in the temporal and central regions during infancy.ConclusionsBrain glycolytic metabolism of [18F]FDG, measured through the SUVmean, increased with age until early adolescence (< 13 years old), showing differences across brain regions. Age, sex, and brain region influence [18F]FDG uptake, with significant hemispheric asymmetries for temporal and central regions.Graphical

Synthesis and Bioevaluation of 2-Styrylquinoxaline Derivatives as Tau-PET Tracers.

This study focused on designing and evaluating Tau-PET tracers for noninvasive positron emission computed tomography (PET) imaging of neurofibrillary tangles (NFTs), a hallmark pathology of Alzheimer's disease (AD). The tracers were synthesized with a 2-styrylquinoxaline scaffold and varying lengths of FPEG chains. The compound [18F]15, which had two ethoxy units, showed high affinity for recombinant K18-Tau aggregates (Ki = 41.48 nM) and the highest selectivity versus Aβ1-42 aggregates (8.83-fold). In vitro autoradiography and fluorescent staining profiles further validated the binding of [18F]15 or 15 toward NFTs in brain sections from AD patients and Tau-transgenic mice. In normal ICR mice, [18F]15 exhibited an ideal initial brain uptake (11.21% ID/g at 2 min) and moderate washout ratio (2.29), and micro-PET studies in rats confirmed its ability to penetrate the blood-brain barrier with the peak SUV value of 1.94 in the cortex. These results suggest that [18F]15 has the potential to be developed into a useful Tau-PET tracer for early AD diagnosis and evaluation of anti-Tau therapeutics.