Alzheimer’s disease is characterized by the deposition of amyloid-beta (Aβ) plaques, necessitating early detection and reliable biomarkers for effective intervention. Non-human primates, particularly aged vervet monkeys, offer valuable models for studying age-related Aβ pathology due to their close phylogenetic relationship to humans and similar neuropathological features. This study assessed the utility of [18F]FC119S, a novel Aβ-targeting PET radiotracer, in aged vervet monkeys. The radiochemistry of [18F]FC119S was optimized and automated to ensure high radiochemical purity and molar activity. PET/MRI imaging was performed to evaluate tracer uptake, distribution, and washout kinetics. Correlations between [18F]FC119S uptake and cerebrospinal fluid (CSF) and plasma biomarkers—including Aβ42/40 ratio, pTau181, neurofilament light chain (NfL), and pTau181/Aβ42 ratio—were analyzed. Autoradiography was conducted to validate regional tracer binding in brain tissues. [18F]FC119S demonstrated high brain uptake, rapid washout, and widespread cortical distribution in vervet monkeys, mirroring patterns observed in human studies. Tracer uptake showed negative associations with CSF Aβ42/40 ratio in Aβ-affected regions, and significant positive correlations with CSF pTau181 and CSF pTau181/Aβ42 ratio in the temporal lobe. Additionally, significant positive correlations were observed between [18F]FC119S uptake and CSF NfL in the anterior cingulate gyrus, parietal, and occipital lobes. Autoradiography confirmed elevated tracer binding in specific brain regions of older vervets with low CSF Aβ42 compared to younger counterparts. These findings validate [18F]FC119S as a promising PET radiotracer for tracking Aβ deposition in aged vervet monkeys. Its imaging characteristics and biomarker correlations support its translational potential for Alzheimer’s disease research and early diagnostic applications.

Microtubules (MTs), as structural components of the cytoskeleton, are vital for axonal transport, information processing, and signaling within the brain. Disruption of MT integrity has been associated with neurological disorders, including alcohol use disorder (AUD). This study used positron emission tomography (PET) imaging with the radiotracer [11C]MPC-6827 to investigate alcohol-induced changes in MT dynamics in a nonhuman primate model of AUD. Dynamic PET scans (0-120 min) were conducted in male cynomolgus monkeys (n = 4) before and after ∼7 months of ethanol self-administration (EtOH SA). Quantitative analysis of standardized uptake values and time-activity curves demonstrated a consistent decrease in [11C]MPC-6827 uptake across multiple brain regions, particularly in the amygdala, globus pallidus, and substantia innominata. Statistically significant reductions in tracer uptake were observed in early scan windows (15 and 30 min), suggesting compromised MT integrity due to chronic EtOH SA. These findings provide compelling evidence that chronic alcohol consumption induces significant changes in microtubule dynamics, potentially contributing to pathological processes underlying AUD.

INTRODUCTION:Microtubule (MT) stability is crucial for proper neuronal function. Understanding MT dysregulation is critical for connecting amyloid beta (Aβ) and tau-based degenerative events and early changes in presymptomatic Alzheimer's disease (AD). Herein we present positron emission tomography (PET) imaging properties of our MT-PET radiotracer, [11C]MPC-6827, in multiple established AD mouse models. METHODS:Longitudinal PET, biodistribution, autoradiography, immunohistochemistry, and behavioral studies were conducted at multiple time points in APPswe/PSEN1dE9 (APP/PS1), P301S-PS19 (P301S), 5xFAD, and age-matched control mice. RESULTS:Longitudinal [11C]MPC-6827 brain imaging showed significant increases in APP/PS1, P301S, and 5xFAD mice compared to controls. Longitudinal MT-PET correlated positively with biodistribution, autoradiography, and immunohistochemistry results and negatively with behavior data. DISCUSSION:Our study demonstrated significant longitudinal [11C]MPC-6827 PET increases in multiple AD mouse models for the first time. Strong correlations between PET and biomarker data underscored the interplay of MT destabilization, amyloid, and tau pathology in AD. These results suggest [11C]MPC-6827 PET as a promising tool for monitoring MT dysregulation early in AD progression. HIGHLIGHTS:Longitudinal positron emission tomography (PET) imaging studies using [11C]MPC-6827 in multiple established Alzheimer's disease (AD) mouse models revealed an early onset of microtubule dysregulation, with significant changes in brain radiotracer uptake evident from 2 to 4 months of age. Intra-group analysis showed a progressive increase in microtubule dysregulation with increasing AD burden, supported by significant correlations between PET imaging data and biodistribution, autoradiography, and molecular pathological markers. [11C]MPC-6827 PET imaging demonstrated its efficacy in detecting early microtubule alterations preceding observable behavioral changes in AD mouse models, suggesting its potential for early AD imaging. The inclusion of the 5xFAD mouse model further elucidated the impact of amyloid beta (Aβ) toxicity on inducing tau hyperphosphorylation-mediated microtubule dysregulation, highlighting the versatility of [11C]MPC-6827 in delineating various aspects of AD pathology. Our study provides immediate clarity on high uptake of the microtubule-based radiotracer in AD brains in a longitudinal setting, which directly informs clinical utility in Aβ/tau-based studies.

Background:Intranasal insulin (INI) is being explored as a treatment for Alzheimer's disease (AD). Improved memory, functional ability, and cerebrospinal fluid (CSF) AD biomarker profiles have been observed following INI administration. However, the method of intranasal delivery may significantly affect outcomes. Objective:To show reliable delivery of insulin to the brain using the Aptar Cartridge Pump System (CPS) intranasal delivery system. Methods:To visualize INI biodistribution, we developed a novel PET radiotracer, Gallium 68-radiolabeled (NOTA-conjugated) insulin, [68Ga]Ga-NOTA-insulin. We used the Aptar CPS to administer [68Ga]Ga-NOTA-insulin to anesthetized healthy adult vervet monkeys and measured brain regional activity and whole-body dosimetry following PET/CT scans. Results:We observed brain penetration of [68Ga]Ga-NOTA-insulin following intranasal administration with the Aptar CPS. Radioactive uptake was seen in multiple regions, including the amygdala, putamen, hypothalamus, hippocampus, and choroid plexus. A safety profile and whole-body dosimetry were also established in a second cohort of vervets. Safety was confirmed: vitals remained stable, blood glucose levels were unchanged, and no organ was exposed to more than 2.5 mSv of radioactivity. Extrapolations from vervet organ distribution allowed for estimation of the [68Ga]Ga-NOTA-insulin absorbed dose in humans, and the maximum dose of [68Ga]Ga-NOTA-insulin that can be safely administered to humans was determined to be 185 MBq. Conclusions:The use of [68Ga]Ga-NOTA-insulin as a PET radiotracer is safe and effective for observing brain uptake in vervet monkeys. Further, the Aptar CPS successfully targets [68Ga]Ga-NOTA-insulin to the brain. The data will be essential in guiding future studies of intranasal [68Ga]Ga-NOTA-insulin administration in humans.

Rapid brain accumulation is critical for the acute reinforcing effects of nicotine. Although nicotine formulation (free-base vs. protonated or salt) in electronic cigarette (E-cig) liquid affects user satisfaction, its impact on brain nicotine accumulation (BNA) from E-cig use has not been evaluated in comparison with traditional combustible cigarettes (C-cigs) using a within-subjects design. BNA was directly assessed with 29 adult dual users (13 females) of E-cigs and C-cigs, using [ 11 C]nicotine and positron emission tomography (PET). Participants underwent two 15-min upper body (from chest to head) scanning sessions during which they inhaled a single puff of [ 11 C]nicotine-labeled vapor from E-cigs with free-base nicotine or C-cig smoke in a randomized order. Seventeen of them also went through another session during which they inhaled from E-cigs with nicotine salt. A full-body scan was also conducted at each session to measure total absorbed dose of [ 11 C]nicotine. Mean maximum nicotine concentration ( C max ) in brain following inhalation of free-base nicotine E-cig vapor was 19% and 15% lower relative to C-cig smoke and nicotine salt E-cig vapor ( p s = 0.014 and 0.043, respectively). The C max values did not differ significantly between the C-cig and nicotine salt E-cig. Mean values of time to the maximum concentration ( T max ) were not significantly different between the two types of E-cig, but they were 64% and 40% longer than that for C-cig smoking ( p s = 0.0005 and 0.004, respectively). Mean C max with C-cigs and free-base nicotine E-cigs were greater in females relative to males and correlated with T 1/2 of lung nicotine clearance and participants’ pack-years. These results suggest that while E-cigs with free-base nicotine formulation can deliver nicotine rapidly to the brain, those with nicotine salt formulation are capable of even more efficient brain nicotine delivery closely resembling combustible cigarettes. Therefore, nicotine formulation or pH in E-liquid should be considered in evaluation of E-cigs in terms of abuse liability and potential in substituting for combustible cigarettes.

The microtubule (MT) instability observed in Alzheimer's disease (AD) is commonly attributed to hyperphosphorylation of the MT-associated protein, tau. In vivo PET imaging offers an opportunity to gain critical information about MT changes with the onset and development of AD and related dementia. We developed the first brain-penetrant MT PET ligand, [11C]MPC-6827, and evaluated its in vivo imaging utility in vervet monkeys. Consistent with our previous in vitro cell uptake and in vivo rodent imaging experiments, [11C]MPC-6827 uptake increased with MT destabilization. Radioactive uptake was inversely related to (cerebrospinal fluid) CSF Aβ42 levels and directly related to age in a nonhuman primate (NHP) model of AD. Additionally, in vitro autoradiography studies also corroborated PET imaging results. Here, we report the preliminary results of PET imaging with [11C]MPC-6827 in four female vervet monkeys with high or low CSF Aβ42 levels, which have been shown to correlate with the Aβ plaque burden, similar to humans.

Impairment and/or destabilization of neuronal microtubules (MTs) resulting from hyper-phosphorylation of the tau proteins is implicated in many pathologies, including Alzheimer's disease (AD), Parkinson's disease and other neurological disorders. Increasing scientific evidence indicates that MT-stabilizing agents protect against the deleterious effects of neurodegeneration in treating AD. To quantify these protective benefits, we developed the first brain-penetrant PET radiopharmaceutical, [11C]MPC-6827, for in vivo quantification of MTs in rodent and nonhuman primate models of AD. Mechanistic insights revealed from recently reported studies confirm the radiopharmaceutical's high selectivity for destabilized MTs. To further translate it to clinical settings, its metabolic stability and pharmacokinetic parameters must be determined. Here, we report in vivo plasma and brain metabolism studies establishing the radiopharmaceutical-binding constants of [11C]MPC-6827. Binding constants were extrapolated from autoradiography experiments; pretreatment with a nonradioactive MPC-6827 decreased the brain uptake >70%. It exhibited ideal binding characteristics (typical of a CNS radiopharmaceutical) including LogP (2.9), Kd (15.59 nM), and Bmax (11.86 fmol/mg). Most important, [11C]MPC-6827 showed high serum and metabolic stability (>95%) in rat plasma and brain samples.

While 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. Male 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. [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). TG 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.

G-protein-coupled receptor 119 (GPR119) has emerged as a promising target for treating type 2 diabetes mellitus. Activating GPR119 improves glucose homeostasis, while suppressing appetite and weight gain. Measuring GPR119 levels in vivo could significantly advance GPR119-based drug development strategies including target engagement, occupancy, and distribution studies. To date, no positron emission tomography (PET) ligands are available to image GPR119. In this paper, we report the synthesis, radiolabeling, and preliminary biological evaluations of a novel PET radiotracer [18F]KSS3 to image GPR119. PET imaging will provide information on GPR119 changes with diabetic glycemic loads and the efficacy of GPR119 agonists as antidiabetic drugs. Our results demonstrate [18F]KSS3's high radiochemical purity, specific activity, cellular uptake, and in vivo and ex vivo uptake in pancreas, liver, and gut regions, with high GPR119 expression. Cell pretreatment with nonradioactive KSS3, rodent PET imaging, biodistribution, and autoradiography studies showed significant blocking in the pancreas showing [18F]KSS3's high specificity.

Background Microtubules (MTs) are critical for cell structure, function, and survival. MT instability may contribute to Alzheimer’s disease (AD) pathogenesis as evidenced by persistent negative regulation (phosphorylation) of the neuronal microtubule-associated protein tau. Hyperphosphorylated tau, not bound to MTs, forms intraneuronal pathology that correlates with dementia and can be tracked using positron emission tomography (PET) imaging. The contribution of MT instability in AD remains unknown, though it may be more proximal to neuronal dysfunction than tau accumulation. Our lab reported the first brain-penetrant MT-based PET ligand, [ 11 C]MPC-6827, and its PET imaging with this ligand in normal rodents and non-human primates demonstrated high brain uptake and excellent pharmacokinetics. Target engagement and mechanism of action using in vitro, in vivo, and ex vivo methods were evaluated here. Methods In vitro cell uptake assay was performed in SH-SY5Y neuronal cells with [ 11 C]MPC-6827, with various MT stabilizing and destabilizing agents. To validate the in vitro results, wild type (WT) mice ( n = 4) treated with a brain-penetrant MT stabilizing drug (EpoD) underwent microPET/CT brain imaging with [ 11 C]MPC-6827. To determine the influence of tau protein on radiotracer binding in the absence of protein accumulation, we utilized tau knockout (KO) mice. In vivo microPET imaging, ex vivo biodistribution, and autoradiography studies were performed in tau KO and WT mice ( n = 6/group) with [ 11 C]MPC-6827. Additionally, α, β, and acetylated tubulin levels in both brain samples were determined using commercially available cytoskeleton-based MT kit and capillary electrophoresis immunoblotting assays. Results Cell uptake demonstrated higher radioactive uptake with MT destabilizing agents and lower uptake with stabilizing agents compared to untreated cells. Similarly, acute treatment with EpoD in WT mice decreased [ 11 C]MPC-6827 brain uptake, assessed with microPET/CT imaging. Compared to WT mice, tau KO mice expressed significantly lower β tubulin, which contains the MPC-6827 binding domain, and modestly lower levels of acetylated α tubulin, indicative of unstable MTs. In vivo imaging revealed significantly higher [ 11 C]MPC-6827 uptake in tau KOs than WT, particularly in AD-relevant brain regions known to express high levels of tau. Ex vivo post-PET biodistribution and autoradiography confirmed the in vivo results. Conclusions Collectively, our data indicate that [ 11 C]MPC-6827 uptake inversely correlates with MT stability and may better reflect the absence of tau than total tubulin levels. Given the radiotracer binding does not require the presence of aggregated tau, we hypothesize that [ 11 C]MPC-6827 may be particularly useful in preclinical stages of AD prior to tau deposition. Our study provides immediate clarity on high uptake of the MT-based radiotracer in AD brains, which directly informs clinical utility in MT/tau-based PET imaging studies.

Purpose:Microtubules (MTs) are structural units made of α and β tubulin subunits in the cytoskeleton responsible for axonal transport, information processing, and signaling mechanisms-critical for healthy brain function. Chronic cocaine exposure affects the function, organization, and stability of MTs in the brain, thereby impairing overall neurochemical and cognitive processes. At present, we have no reliable, non-invasive methods to image MTs for cocaine use disorder (CUD). Recently we reported the effect of cocaine in patient-derived neuroblastoma SH-SY5Y cells. Here we report preliminary results of a potential imaging biomarker of CUD using the brain penetrant MT-based radiotracer, [11C]MPC-6827, in an established rodent model of cocaine self-administration (SA).Methods:Cell uptake studies were performed with [11C]MPC-6827 in SH-SY5Y cells, treated with or without cocaine (n = 6/group) at 30 and 60 min incubations. MicroPET/CT brain scans were performed in rats at baseline and 35 days after cocaine self-administration and compared with saline-treated rats as controls (n = 4/sex). Whole-body post-PET biodistribution, plasma metabolite assay, and brain autoradiography were performed in the same rats from imaging.Results:Cocaine-treated SH-SY5Y cells demonstrated a ∼26(±4)% decrease in radioactive uptake compared to non-treated controls. Both microPET/CT imaging and biodistribution results showed lower (∼35 ± 3%) [11C]MPC-6827 brain uptake in rats that had a history of cocaine self-administration compared to the saline-treated controls. Plasma metabolite assays demonstrate the stability (≥95%) of the radiotracer in both groups. In vitro autoradiography also demonstrated lower radioactive uptake in cocaine rats compared to the control rats. [11C]MPC-6827's in vitro SH-SY5Y neuronal cell uptake, in vivo positron emission tomography (PET) imaging, ex vivo biodistribution, and in vitro autoradiography results corroborated well with each other, demonstrating decreased radioactive brain uptake in cocaine self-administered rats versus controls. There were no significant differences either in cocaine intake or in [11C]MPC-6827 uptake between the male and female rats.Conclusions:This project is the first to validate in vivo imaging of the MT-associations with CUD in a rodent model. Our initial observations suggest that [11C]MPC-6827 uptake decreases in cocaine self-administered rats and that it may selectively bind to destabilized tubulin units in the brain. Further longitudinal studies correlating cocaine intake with [11C]MPC-6827 PET brain measures could potentially establish the MT scaffold as an imaging biomarker for CUD, providing researchers and clinicians with a sensitive tool to better understand the biological underpinnings of CUD and tailor new treatments.

Microtubule (MT) integrity is critical for cell function and viability. Abnormal MT-stability in AD is commonly attributed to hyperphosphorylation of the MT-associated protein, tau. However, the time course of MT instability in disease progression remains unknown. In vivo MT imaging offers an opportunity to gain critical information on MT changes in relation to staging of ADRDs. Our lab reported the first brain-penetrant MT PET ligand, [ 11 C]MPC-6827 and evaluated in vivo imaging in normal rodents and non-human primates (NHP). Herein we report its initial biological evaluations in (a) neuronal cells, (b) tau knock-out mice, and (c) aged NHPs (Caribbean-origin vervets) with changes in AD-related biomarkers. In vitro [ 11 C]MPC-6827 cell uptake assay was performed in patient-derived SH-SY5Y cells with different MT destabilizing and stabilizing agents. Radioactive binding efficiency was determined as %ID (injected dose)/mg of protein present in each well. Dynamic 0-60 min brain microPET/CT imaging was performed in tau knock-out and wild type mice (n=4). Four vervets (20-29y) with different cerebrospinal fluid (CSF) Aβ42 levels (2 high levels-1461, 1614 and 2 low levels-579,732) underwent 0-120 min brain PET/CT imaging with [ 11 C]MPC-6827. ROIs were drawn on the whole-brain and SUVR values were calculated from co-registered PET/MR images. In vitro cell uptake assays with [ 11 C]MPC-6827 in SH-SY5Y cells displayed high uptake with MT destabilizing agents and low uptake with stabilizing agents. MicroPET imaging demonstrated higher radioactive brain uptake in tau knockout over wild-type mice. Vervets with low CSF Aβ42 levels showed high radioactive brain uptake and the youngest vervet (20y) displayed lowest brain uptake. Consistent with our in vitro cell uptake and in vivo rodent imaging experiments, [ 11 C]MPC-6827 increased with MT destabilizations. Radioactive uptake was inversely related to CSF Aβ levels and directly related to age in a NHP model of AD (Fig 1). Collectively our data suggest that [ 11 C]MPC-6827 is more selective towards destabilized MTs. On-going experiments include rigorous PET imaging analyses, determination of metabolic plasma-blood parameters, and correlations with Aβ42 and tau levels. Nonetheless, our promising results support the high translational utility of [ 11 C]MPC-6827 to image MTs in ADRDs.

G-protein-coupled receptors (GPCRs) plays a key role in regulating glucose metabolism. While GPR119 (an important GPCR) agonists have shown potential for improving neurologic and cognitive function in patients with AD and type2 diabetes mellitus (T2DM), clinical interventions targeting GPR119 will require accurate in vivo measures such as PET imaging. We recently synthesized a series of novel piperdine analogs, identifying two analogs (T1 and T2) with high GPR119 binding potency (2-5 nM) for PET radiochemistry. Here we report their radiochemistry and initial biological evaluations in neuronal cells, normal rodents, and monkeys (vervets). [ 18 F]T1/T2 radiochemistry was performed in TRASIS-AIO automated module following [ 18 F]¯-based nucleophilic substitution of corresponding precursors. [ 18 F]T1 and T2 in vitro assays were performed in three patient-derived cell lines with different GPR119 expression (MDM-MD-23198%) and specific activities (∼3800-4500 mCi/µmol), decay corrected to end of synthesis. Radioactive cell uptake was lower in MDM-MD-231 cells (lowest GPR119 expression) and higher in HepG2 cells (higher GPR119 expression); uptake also significantly increased with GPR119 agonists and T1/T2 treatments compared to baseline. [ 18 F]T2 showed slightly better brain uptake in mice compared to [ 18 F]T1 (SUV max = 0.35±0.07 Vs. 0.55±0.09 g/mL). Biodistribution of [ 18 F]T2 (%ID/mg = 1.01±0.09) also showed high brain uptake. SUV max (avg=2.6±0.1 g/mL) and TACs of both [ 18 F]T1 and [ 18 F]T2 in monkey brains demonstrated rapid distribution across BBB within 10 min and favorable clearance within 90 min of tracer injection ( Fig 1 ). Radiochemistry was successfully automated and optimized. Cell uptake showed direct relationships between radiotracer uptake and GPR119 expression. MicroPET imaging, biodistribution in rodents and monkey PET imaging demonstrated excellent brain uptake and favorable pharmacokinetics, indicating BBB penetration. These data suggest for the first time that [ 18 F]T1 and T2 have potential for imaging GPR119 in brains of humans with AD or T2DM.

Microtubule (MT) integrity is critical for cell function and viability. Abnormal MT stability is commonly attributed to hyperphosphorylation of the MT-associated protein, tau. However, the time course of MT instability in disease progression remains unknown. In vivo MT imaging offers an opportunity to gain critical information on MT changes in relation to staging of ADRDs. Our lab reported the first brain-penetrant MT PET ligand, [ 11 C]MPC-6827 and evaluated in vivo imaging in normal rodents and non-human primates (NHP). Herein we report its initial biological evaluations in (a) cells, (b) tau knock-out mice, and (c) aged NHPs (Caribbean-origin vervets) with changes in AD-related biomarkers. In vitro [ 11 C]MPC-6827 cell uptake assay was performed in patient-derived SH-SY5Y cells with different MT destabilizing and stabilizing agents. Radioactive binding was determined as %ID(injected dose)/mg of protein present in each well. Dynamic 0-60 min brain microPET/CT imaging was performed in tau knock-out and wild-type mice (n=4). Four vervets (20-29y) with different cerebrospinal fluid (CSF) Aβ42 levels (2 high levels-1461, 1614 and 2 low levels-579,732) underwent 0-120 min brain PET/CT imaging with [ 11 C]MPC-6827. ROIs were drawn on the whole-brain and SUVR values were calculated from co-registered PET/MR images. In vitro cell uptake assays with [ 11 C]MPC-6827 in SH-SY5Y cells displayed high uptake with MT destabilizing agents and low uptake with stabilizing agents. MicroPET imaging demonstrated higher radioactive brain uptake in tau knockout over wild-type mice. Vervets with low CSF Aβ42 levels showed high radioactive brain uptake and the youngest vervet (20y) displayed lowest brain uptake. Consistent with our in vitro cell uptake and in vivo rodent imaging experiments, [ 11 C]MPC-6827 increased with MT destabilizations. Radioactive uptake was inversely related to CSF Aβ levels and directly related to age in a NHP model of AD (Fig 1). Collectively our data suggest that [ 11 C]MPC-6827 is more selective towards destabilized MTs. On-going experiments include rigorous PET imaging analyses, determination of metabolic plasma-blood parameters, and correlations with Aβ42 and tau levels. Nonetheless, our promising results support the high translational utility of [ 11 C]MPC-6827 to image MTs in ADRDs.

Over production of reactive oxygen species (ROS) caused by altered redox regulation of signaling pathways is common in many types of cancers. While PET imaging is recognized as the standard tool for cancer imaging, there are no clinically-approved PET radiotracers for ROS-imaging in cancer diagnosis and treatment. An ascorbate-based radio ligand promises to meet this urgent need. Our laboratory recently synthesized [18F] KS1, a fluoroethoxy furanose ring-containing ascorbate derivative, to track ROS in prostate tumor-bearing mice. Here we report cell uptake assays of [18F]KS1 with different ROS-regulating agents, PET imaging in head and neck squamous cell carcinoma (HNSCC) mice, and doxorubicin-induced rats; PET imaging in healthy and irradiated hepatic tumor-bearing rhesus to demonstrate its translational potential. Our preliminary evaluations demonstrated that KS1 do not generate ROS in tumor cells at tracer-level concentrations and tumor-killing properties at pharmacologic doses. [18F]KS1 uptake was low in HNSCC pretreated with ROS blockers, and high with ROS inducers. Tumors in high ROS-expressing SCC-61 took up significantly more [18F]KS1 than rSCC-61 (low-ROS expressing HNSCC); high uptake in doxorubicin-treated rats compared to saline-treated controls. Rodent biodistribution and PET imaging of [18F]KS1 in healthy rhesus monkeys demonstrated its favorable safety, pharmacokinetic properties with excellent washout profile, within 3.0 h of radiotracer administration. High uptake of [18F]KS1 in liver tumor tissues of the irradiated hepatic tumor-bearing monkey showed target selectivity. Our strong data in vitro, in vivo, and ex vivo here supports the high translational utility of [18F]KS1 to image ROS.

1480 Objectives: Ascorbic acid is a potent, biological antioxidant. It scavenges most reactive oxygen species (ROS) that could otherwise damage nucleic acids and promote carcinogenesis. Its potential anti-tumor effects are being studied, with many reporting the slowing of tumor growth at pharmacologic doses.At the same time, lower doses of ascorbate can be used to image/track ROS. However, the complete in vivo molecular ROS mechanisms of ascorbate in cancer largely remain unknown. PET imaging with a new generation of ascorbate-based radioligand can present an opportunity for in vivo assessment of ROS in cancer. Our laboratory reported the initial PET imaging properties of a novel ascorbate derivative, [18F]KS1, to track ROS in tumor-bearing mice (EJNMMI 2019, 9(1):43). We demonstrated high ROS binding affinity in head and neck and prostate cancer cells through cell uptake assays, microPET imaging, and biodistribution studies. Rhesus monkeys exposed to radiation experience increased target tissue ROS and persistent systemic inflammation for years after exposure. Therefore, forms an ideal animal model to validate our PET radioligand strategy to image ROS in vivo. Herein, we report the preliminary PET imaging evaluations of [18F]KS1 in normal/non-irradiated rhesus monkeys and established NHP tumor model of radiation exposure. Methods: All the NHPs were placed in the scanner and a catheter was inserted into an external vein for tracer injection. Body temperature was maintained at 40 °C with a warm air circulating blanket and vital signs including heart rate, blood pressure, respiration rate, and temperature were monitored throughout the scanning procedure. PET/CT images were acquired in both normal (n=2, 8-9 y, 8.8-9 kg) and radiated (~8 Gy radiation) renal and hepatic tumor-bearing (n=2, 9-10 y, 10-12 kg) rhesus macaques with a dose of [18F]KS1 (8 ± 1 mCi). Whole-body scanning was performed at multiple time points in the non-irradiated monkeys i.e., every 30 min post-radiotracer injection until 3.0 h, and one-time point for the tumor-bearing monkeys i.e., 90 min post-radiotracer injection. ROIs were drawn manually on the fused PET/CT images across the kidneys, liver, lungs, brain, heart, tumor, and muscle using the PMOD software analyses, and SUVavg were calculated. Additionally, ex vivo ROS was determined in the tumor and muscle tissues (collected by biopsy) from the tumor-bearing monkey using an OxylHC histopathology detection kit. Results: Whole-body PET imaging biodistribution profile based on SUVavg values in normal rhesus monkeys demonstrated excellent washout kinetics from all critical organs from 30 min to 180 min post-injection including kidneys (84.3 to 5.60 KBq/cc), liver (37.7 to 9.1 KBq/cc), heart (11.3 to 1.34 KBq/cc), lungs (16.86 to 2.53 KBq/cc), and brain (2.11 to 0.31 KBq/cc). More importantly, both the tumor-bearing monkeys demonstrated ~8-fold higher tumor to muscle ratio (72.23 Vs. 9.21 KBq/cc), and the radioactivity profile in the rest of the other organs was similar to the distribution kinetics in normal monkeys at 90 min time-point. No significant bone uptake was observed, demonstrating no defluorination of the radiotracer. Vital signs remained stable throughout the scanning procedure indicating the safety profile of [18F]KS1 in NHPs. OxylHC histopathology assay results demonstrated ~6.5-fold high ROS ex vivo in tumor (target) tissue compared to the muscle (non-target). Conclusions: Initial PET imaging evaluations of [18F]KS1 in NHP tumor model of radiation exposure exhibited (a) favorable pharmacokinetic properties, (b) high tumor uptake in vivo, (c) superior ROS in vivo selectivity (well-corroborated with the ex vivo measurements). These strong preliminary data support the high translational utility of [18F]KS1 to track ROS in vivo. Blood metabolite studies, dosimetry studies are being investigated in our lab to evaluate the comprehensive PET imaging properties of [18F]KS1.

Microtubules (MTs) are structural units in the cytoskeleton. In brain cells they are responsible for axonal transport, information processing, and signaling mechanisms. Proper function of these processes is critical for healthy brain functions. Alcohol and substance use disorders (AUD/SUDs) affects the function and organization of MTs in the brain, making them a potential neuroimaging marker to study the resulting impairment of overall neurobehavioral and cognitive processes. Our lab reported the first brain-penetrant MT-tracking Positron Emission Tomography (PET) ligand [11C]MPC-6827 and demonstrated its in vivo utility in rodents and non-human primates. To further explore the in vivo imaging potential of [11C]MPC-6827, we need to investigate its mechanism of action. Here, we report preliminary in vitro binding results in SH-SY5Y neuroblastoma cells exposed to ethanol (EtOH) or cocaine in combination with multiple agents that alter MT stability. EtOH and cocaine treatments increased MT stability and decreased free tubulin monomers. Our initial cell-binding assay demonstrated that [11C]MPC-6827 may have high affinity to free/unbound tubulin units. Consistent with this mechanism of action, we observed lower [11C]MPC-6827 uptake in SH-SY5Y cells after EtOH and cocaine treatments (e.g., fewer free tubulin units). We are currently performing in vivo PET imaging and ex vivo biodistribution studies in rodent and nonhuman primate models of AUD and SUDs and Alzheimer's disease.

Microtubules (MTs) are structural units in the cytoskeleton. In brain cells they are responsible for axonal transport, information processing, and signaling mechanisms. Proper function of these processes is critical for healthy brain functions. Alcohol and substance use disorders (AUD/SUDs) affects the function and organization of MTs in the brain, making them a potential neuroimaging marker to study the resulting impairment of overall neurobehavioral and cognitive processes. Our lab reported the first brain-penetrant MT-tracking Positron Emission Tomography (PET) ligand [ 11 C]MPC-6827 and demonstrated its in vivo utility in rodents and non-human primates. To further explore the in vivo imaging potential of [ 11 C]MPC-6827, we need to investigate its mechanism of action. Here, we report preliminary in vitro binding results in SH-SY5Y neuroblastoma cells exposed to ethanol (EtOH) or cocaine in combination with multiple agents that alter MT stability. EtOH and cocaine treatments increased MT stability and decreased free tubulin monomers. Our initial cell-binding assay demonstrated that [ 11 C]MPC-6827 selectively bound to free/unbound tubulin units. Consistent with this mechanism of action, we observed lower [ 11 C]MPC-6827 uptake in SH-SY5Y cells after EtOH and cocaine treatments (e.g., fewer free tubulin monomers). We are currently performing in vivo PET imaging and ex vivo biodistribution studies in rodent and nonhuman primate models of AUD and SUDs.