Comparison of novel PSMA-targeting [177Lu]Lu-P17-087 with its albumin binding derivative [177Lu]Lu-P17-088 in metastatic castration-resistant prostate cancer patients: a first-in-human study.

PURPOSE: Prostate-specific membrane antigen (PSMA) is a promising target for diagnosis and radioligand therapy (RLT) of prostate cancer. Two novel PSMA-targeting radionuclide therapy agents, [177Lu]Lu-P17-087, and its albumin binder modified derivative, [177Lu]Lu-P17-088, were evaluated in metastatic castration-resistant prostate cancer (mCRPC) patients. The primary endpoint was dosimetry evaluation, the second endpoint was radiation toxicity assessment (CTCAE 5.0) and PSA response (PCWG3). METHODS: Patients with PSMA-positive tumors were enrolled after [68Ga]Ga-PSMA-11 PET/CT scan. Five mCRPC patients received [177Lu]Lu-P17-087 and four other patients received [177Lu]Lu-P17-088 (1.2 GBq/patient). Multiple whole body planar scintigraphy was performed at 1.5, 4, 24, 48, 72, 120 and 168 h after injection and one SPECT/CT imaging was performed at 24 h post-injection for each patient. Dosimetry evaluation was compared in both patient groups. RESULTS: Patients showed no major clinical side-effects under this low dose treatment. As expected [177Lu]Lu-P17-088 with longer blood circulation (due to its albumin binding) exhibited higher effective doses than [177Lu]Lu-P17-087 (0.151 ± 0.036 vs. 0.056 ± 0.019 mGy/MBq, P = 0.001). Similarly, red marrow received 0.119 ± 0.068 and 0.048 ± 0.020 mGy/MBq, while kidney doses were 0.119 ± 0.068 and 0.046 ± 0.022 mGy/MBq, respectively. [177Lu]Lu-P17-087 demonstrated excellent tumor uptake and faster kinetics; while [177Lu]Lu-P17-088 displayed a slower washout and higher average dose (7.75 ± 4.18 vs. 4.72 ± 2.29 mGy/MBq, P = 0.018). After administration of [177Lu]Lu-P17-087 and [177Lu]Lu-P17-088, 3/5 and 3/4 patients showed reducing PSA values, respectively. CONCLUSION: [177Lu]Lu-P17-088 and [177Lu]Lu-P17-087 displayed different pharmacokinetics but excellent PSMA-targeting dose delivery in mCRPC patients. These two agents are promising RLT agents for personalized treatment of mCRPC. Further studies with increased dose and frequency of RLT are warranted to evaluate the potential therapeutic efficacy. TRIAL REGISTRATION: 177Lu-P17-087/177Lu-P17-088 in Patients with Metastatic Castration-resistant Prostate Cancer (NCT05603559, Registered at 25 October, 2022). URL OF REGISTRY: https://classic. CLINICALTRIALS: gov/ct2/show/NCT05603559 .

First-in-human study of PSMA-targeting agent, [18F]AlF-P16-093: dosimetry and initial evaluation in prostate cancer patients.

PURPOSE: This is a first-in-human study to evaluate the radiation dosimetry of a new prostate-specific membrane antigen (PSMA)-targeted radiopharmaceutical, [18F]AlF-P16-093, and also initial investigation of its ability to detect PSMA-positive tumors using PET scans in a cohort of prostate cancer (PCa) patients. METHODS: The [18F]AlF-P16-093 was automatically synthesized with a GE TRACERlab. A total of 23 patients with histopathologically proven PCa were prospectively enrolled. Dosimetry and biodistribution study investigations were carried out on a subset of six (6) PCa patients, involving multiple time-point scanning. The mean absorbed doses were estimated with PMOD and OLINDA software. RESULTS: [18F]AlF-P16-093 was successfully synthesized, and radiochemical purity was > 95%, and average labeling yield was 36.5 ± 8.3% (decay correction, n = 12). The highest tracer uptake was observed in the kidneys, spleen, and liver, contributing to an effective dose of 16.8 ± 1.3 µSv/MBq, which was ~ 30% lower than that of [68Ga]Ga-P16-093. All subjects tolerated the PET examination well, and no reportable side-effects were observed. The PSMA-positive tumors displayed rapid uptake, and they were all detectable within 10 min, and no additional lesions were observed in the following multi-time points scanning. Each patient had at least one detectable tumor lesion, and a total of 356 tumor lesions were observed, including intraprostatic, lymph node metastases, bone metastases, and other soft tissue metastases. CONCLUSIONS: We report herein a streamlined method for high yield synthesis of [18F]AlF-P16-093. Preliminary study in PCa patients has demonstrated its safety and acceptable radiation dosimetry. The initial diagnostic study indicated that [18F]AlF-P16-093 PET/CT is efficacious and potentially useful for a widespread application in the diagnosis of PCa patients.

Determining the optimal pharmacokinetic modelling and simplified quantification method of [18F]AlF-P16-093 for patients with primary prostate cancer (PPCa).

PURPOSE: This paper discusses the optimization of pharmacokinetic modelling and alternate simplified quantification method for [18F]AlF-P16-093, a novel tracer for in vivo imaging of prostate cancer. METHODS: Dynamic PET/CT scans were conducted on eight primary prostate cancer patients, followed by a whole-body scan at 60 min post-injection. Time-activity curves (TACs) were obtained by drawing volumes of interest for primary prostatic and metastatic lesions. Optimal kinetic modelling involved evaluating three compartmental models (1T2K, 2T3K, and 2T4K) accounting for fractional blood volume (Vb). The simplified quantification method was then determined based on the correlation between the static uptake measure and total distribution volume (Vt) obtained from the optimal pharmacokinetic analysis. RESULTS: In total, 17 intraprostatic lesions, 10 lymph nodes, and 36 osseous metastases were evaluated. Visually, the contrast of the tumor increased and showed the steepest incline within the first few minutes, whereas background activity decreased over time. Full pharmacokinetic analysis revealed that a reversible two-compartmental (2T4K) model is the preferred kinetic model for the given tracer. The kinetic parameters K1, k3, Vb, and Vt were all significantly higher in lesions when compared with normal tissue (P < 0.01). Several simplified protocols were tested for approximating comprehensive dynamic quantification in tumors, with image-based SURmean (the ratio of tumor SUVmean to blood SUVmean) within the 28-34 min window found to be sufficient for approximating the total distribution Vt values (R2 = 0.949, P < 0.01). Both Vt and SURmean correlated significantly with the total serum prostate-specific antigen (tPSA) levels (P < 0.01). CONCLUSIONS: This study introduced an optimized pharmacokinetic modelling approach and a simplified acquisition method for [18F]AlF-P16-093, a novel PSMA-targeted radioligand, highlighting the feasibility of utilizing one static PET imaging (between 30 and 60 min) for the diagnosis of prostate cancer. Note that the image-derived input function in this study may not reflect the true corrected plasma input function, therefore the interpretation of the associated kinetic parameter estimates should be done with caution.

Relationship of estrogen synthesis capacity in the brain with obesity and self-control in men and women.

Gonadal hormones are linked to mechanisms that govern appetitive behavior and its suppression. Estrogens are synthesized from androgens by the enzyme aromatase, highly expressed in the ovaries of reproductive-aged women and in the brains of men and women of all ages. We measured aromatase availability in the amygdala using positron emission tomography (PET) with the aromatase inhibitor [11C]vorozole in a sample of 43 adult, normal-weight, overweight, or obese men and women. A subsample of 27 also completed personality measures to examine the relationship between aromatase and personality traits related to self-regulation and inhibitory control. Results indicated that aromatase availability in the amygdala was negatively associated with body mass index (BMI) (in kilograms per square meter) and positively correlated with scores of the personality trait constraint independent of sex or age. Individual variations in the brain's capacity to synthesize estrogen may influence the risk of obesity and self-control in men and women.

Radiolabeling Optimization and Preclinical Evaluation of the New PSMA Imaging Agent [18F]AlF-P16-093.

Prostate-specific membrane antigen (PSMA)-targeted radioligands have played an increasing role in the diagnosis of prostate cancer. [68Ga]Ga-P16-093 is a PSMA-targeting agent for positron emission tomography imaging, currently under a Phase 2 clinical trial. In the present study, P16-093 was labeled with 18F via [18F]AlF2+ complex formation, and the biological properties of [18F]AlF-P16-093 were evaluated. Optimization of radiolabeling efficiency was performed by testing a series of parameters, including the amount of free ligand; the amount of Al3+; and the influence of solvent, pH, temperature, reaction time, and reaction volume. Optimal labeling results were achieved at pH 5 by reacting at 60 °C for 15 min in a vial containing 74-370 MBq of [18F]fluoride, 46 nmol of P16-093, 40 nmol of AlCl3·6 H2O, and 50% EtOH. [18F]AlF-P16-093 was prepared with a non-decay-corrected radiochemical yield of 54.4 ± 4.4% (n = 9) within 30 min (final radiochemical purity ≥95%). In vitro, [18F]AlF-P16-093 showed PSMA-specific high uptakes in PIP-PC3 cells. The binding affinity of [18F]AlF-P16-093 to PSMA was determined as Kd of 12.4 ± 2.0 nM. The tumor uptake in mice with a xenografted PSMA-expressing PIP-PC3 tumor was high (18.8 ± 5.14% ID/g at 1 h postinjection) and retained without washout for 2 h. In addition, tumor uptake was almost completely blocked by coinjecting a PSMA inhibitor, 2-PMPA. The bone activity at 1 h post injection was higher with [18F]AlF-P16-093 (2.83 ± 0.49% ID/g) in comparison to that of [68Ga]Ga-P16-093 (0.26 ± 0.07% ID/g). In summary, an efficient and simple radiosynthesis of [18F]AlF-P16-093 was achieved. [18F]AlF-P16-093 showed desirable in vivo pharmacokinetics and excellent PSMA-targeting properties for imaging PSMA expression in prostate cancer.

Synthesis and Evaluation of 68Ga- and 177Lu-Labeled (R)- vs (S)-DOTAGA Prostate-Specific Membrane Antigen-Targeting Derivatives.

Prostate-specific membrane antigen (PSMA) is overexpressed in prostate cancer cells and therefore is an attractive target for prostate cancer diagnosis and radionuclide therapy. Recently, published results from clinical studies using a new PSMA-targeting PET imaging agent, [68Ga]Ga-PSMA-093 ([68Ga]Ga-HBED-CC-O-carboxymethyl-Tyr-CO-NH-Glu), support the development of this agent for the diagnosis of prostate cancer. In this study, the HBED-CC chelating group in PSMA-093 was replaced by stereoselective (R)- or (S)-DOTAGA. This chelating group serves not only for chelating 68Ga but is also amendable for complexing other radioactive metals for radionuclide therapy. The corresponding optically pure (R)- and (S)-[68Ga/177Lu]-DOTAGA derivatives, (R)-[68Ga/177Lu]-13 and (S)-[68Ga/177Lu]-13, were successfully prepared. Comparison of radiolabeling, binding affinity, cell uptake, and biodistribution between the two isomers was performed. Radiolabeling of (R)-[177Lu]Lu-13 and (S)-[177Lu]Lu-13 at 50 °C suggested that rates of complex formation were time-dependent and the formation of (S)-[177Lu]Lu-13 was distinctly faster. The rates of complex formation for the corresponding 68Ga agents were comparable between structural isomers. The natGa and natLu equivalents showed high binding PSMA affinity (IC50 = 24-111 nM), comparable to that of the parent agent, [natGa]Ga-PSMA-093 (IC50 = 34.0 nM). Results of cell uptake and biodistribution studies in PSMA-expressing PC3-PIP tumor-bearing mice appeared to show no difference between the labeled (R)- and (S)-isomers. This is the first time that a pair of [68Ga/177Lu]-(R)- and (S)-DOTAGA isomers of PSMA agents were evaluated. Results of biological studies between the isomers showed no noticeable difference; however, the distinctions on the rate of Lu complex formation should be considered in the development of new 177Lu-DOTAGA-based radionuclide therapy agents in the future.

A New [68Ga]Ga-HBED-CC-Bisphosphonate as a Bone Imaging Agent.

Positron emission tomography (PET) imaging using 68Ga-labeled bisphosphonates to target bone metastasis could be a valuable tool in cancer diagnosis and monitoring therapeutic treatment. A 68Ga labeled ligand, N,N'-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N'-diacetic acid (HBED-CC) containing one bisphosphonate group (HBED-CC-BP, 1) was prepared and evaluated. The new ligand, 1, reacted rapidly to form [68Ga]Ga-1, via complexing with [68Ga]GaCl3 eluted from a commercially available 68Ge/68Ga generator (in a sodium acetate buffer at pH 4, reaching >95% labeling yield at room temperature in 5 min). The resulting [68Ga]Ga-1 showed excellent stability in vitro and in vivo. [68Ga]Ga-1 displayed high binding affinity to hydroxyapatite and good uptake in the tibia and femur bone of normal mice. Biodistribution and MicroPET imaging studies of [68Ga]Ga-1 in normal mice and rats showed excellent bone uptake and retention comparable to that of Na[18F]F. The results suggested that [68Ga]Ga-1 might be suitable as a bone imaging agent in humans and it could be useful as a convenient alternative to the current bone imaging PET agent, Na[18F]F, without the need of a near-by cyclotron. Also, an automated synthesis module was developed to produce clinical doses of [68Ga]Ga-1 in a consistent and reproducible manner. Currently, the investigation new drug application (IND) for [68Ga]Ga-HBED-CC-BP, [68Ga]Ga-1, has received FDA approval, and it is currently under clinical trial (IND #129870).

Synthesis and evaluation of novel radioiodinated PSMA targeting ligands for potential radiotherapy of prostate cancer.

Radioligand therapy (RLT) using prostate-specific membrane antigen (PSMA) targeting ligands is an attractive option for the treatment of Prostate cancer (PCa) and its metastases. We report herein a series of radioiodinated glutamate-urea-lysine-phenylalanine derivatives as new PSMA ligands in which l-tyrosine and l-glutamic acid moieties were added to increase hydrophilicity concomitant with improvement of in vivo targeting properties. Compounds 8, 15, 19a/19b and 23a/23b were synthesized and radiolabeled with 125I by iododestannylation. All iodinated compounds displayed high binding affinities toward PSMA (IC50 = 1-13 nM). In vitro cell uptake studies demonstrated that compounds containing an l-tyrosine linker moiety (8, 15 and 19a/19b) showed higher internalization than MIP-1095 and 23a/23b, both without the l-tyrosine linker moiety. Biodistribution studies in mice bearing PC3-PIP and PC3 xenografts showed that [125I]8 and [125I]15 with higher lipophilicity exhibited higher nonspecific accumulations in the liver and intestinal tract, whereas [125I]19a/19b and [125I]23a/23b containing additional glutamic acid moieties showed higher accumulations in the kidney and implanted PC3-PIP (PSMA+) tumors. [125I]23b displayed a promising biodistribution profile with favorable tumor retention, fast clearance from the kidney, and 2-3-fold lower uptake in the liver and blood than that observed for [125I]MIP-1095. [125/131I]23b may serve as an optimal PSMA ligand for radiotherapy treatment of prostate cancer over-expressing PSMA.

Synthesis of l-[4-11 C]Asparagine by Ring-Opening Nucleophilic 11 C-Cyanation Reaction of a Chiral Cyclic Sulfamidate Precursor.

The development of a convenient and rapid method to synthesize radiolabeled, enantiomerically pure amino acids (AAs) as potential positron emission tomography (PET) imaging agents for mapping various biochemical transformations in living organisms remains a challenge. This is especially true for the synthesis of carbon-11-labeled AAs given the short half-life of carbon-11 (11 C, t1/2 =20.4 min). A facile synthetic pathway to prepare enantiomerically pure 11 C-labeled l-asparagine was developed using a partially protected serine as a starting material with a four-step transformation providing a chiral five-membered cyclic sulfamidate as the radiolabeling precursor. Its structure and absolute configuration were confirmed by X-ray crystallography. Utilizing a [11 C]cyanide nucleophilic ring opening reaction followed by selective acidic hydrolysis and deprotection, enantiomerically pure l-[4-11 C]asparagine was synthesized. Further optimization of reaction parameters, including base, metal ion source, solvent, acid component, reaction temperature and reaction time, a reliable two-step method for synthesizing l-[4-11 C]asparagine was presented: within a 45±3 min (n=5, from end-of-bombardment), the desired enantiomerically pure product was synthesized with the initial nucleophilic cyanation yield of 69±4 % (n=5) and overall two-step radiochemical yield of 53±2 % (n=5) based on starting [11 C]HCN, and with radiochemical purity of 96±2 % (n=5).

Dynamic Precision Phenotyping Reveals Mechanism of Crop Tolerance to Root Herbivory.

The western corn rootworm (WCR; Diabrotica virgifera virgifera LeConte) is a major pest of maize (Zea mays) that is well adapted to most crop management strategies. Breeding for tolerance is a promising alternative to combat WCR but is currently constrained by a lack of physiological understanding and phenotyping tools. We developed dynamic precision phenotyping approaches using 11C with positron emission tomography, root autoradiography, and radiometabolite flux analysis to understand maize tolerance to WCR Our results reveal that WCR attack induces specific patterns of lateral root growth that are associated with a shift in auxin biosynthesis from indole-3-pyruvic acid to indole-3-acetonitrile. WCR attack also increases transport of newly synthesized amino acids to the roots, including the accumulation of Gln. Finally, the regrowth zones of WCR-attacked roots show an increase in Gln turnover, which strongly correlates with the induction of indole-3-acetonitrile-dependent auxin biosynthesis. In summary, our findings identify local changes in the auxin biosynthesis flux network as a promising marker for induced WCR tolerance.

Decreased dopamine brain reactivity in marijuana abusers is associated with negative emotionality and addiction severity.

Moves to legalize marijuana highlight the urgency to investigate effects of chronic marijuana in the human brain. Here, we challenged 48 participants (24 controls and 24 marijuana abusers) with methylphenidate (MP), a drug that elevates extracellular dopamine (DA) as a surrogate for probing the reactivity of the brain to DA stimulation. We compared the subjective, cardiovascular, and brain DA responses (measured with PET and [(11)C]raclopride) to MP between controls and marijuana abusers. Although baseline (placebo) measures of striatal DA D2 receptor availability did not differ between groups, the marijuana abusers showed markedly blunted responses when challenged with MP. Specifically, compared with controls, marijuana abusers had significantly attenuated behavioral ("self-reports" for high, drug effects, anxiety, and restlessness), cardiovascular (pulse rate and diastolic blood pressure), and brain DA [reduced decreases in distribution volumes (DVs) of [(11)C]raclopride, although normal reductions in striatal nondisplaceable binding potential (BPND)] responses to MP. In ventral striatum (key brain reward region), MP-induced reductions in DVs and BPND (reflecting DA increases) were inversely correlated with scores of negative emotionality, which were significantly higher for marijuana abusers than controls. In marijuana abusers, DA responses in ventral striatum were also inversely correlated with addiction severity and craving. The attenuated responses to MP, including reduced decreases in striatal DVs, are consistent with decreased brain reactivity to the DA stimulation in marijuana abusers that might contribute to their negative emotionality (increased stress reactivity and irritability) and addictive behaviors.

In vivo quantitative imaging of photoassimilate transport dynamics and allocation in large plants using a commercial positron emission tomography (PET) scanner.

BACKGROUND: Although important aspects of whole-plant carbon allocation in crop plants (e.g., to grain) occur late in development when the plants are large, techniques to study carbon transport and allocation processes have not been adapted for large plants. Positron emission tomography (PET), developed for dynamic imaging in medicine, has been applied in plant studies to measure the transport and allocation patterns of carbohydrates, nutrients, and phytohormones labeled with positron-emitting radioisotopes. However, the cost of PET and its limitation to smaller plants has restricted its use in plant biology. Here we describe the adaptation and optimization of a commercial clinical PET scanner to measure transport dynamics and allocation patterns of (11)C-photoassimilates in large crops. RESULTS: Based on measurements of a phantom, we optimized instrument settings, including use of 3-D mode and attenuation correction to maximize the accuracy of measurements. To demonstrate the utility of PET, we measured (11)C-photoassimilate transport and allocation in Sorghum bicolor, an important staple crop, at vegetative and reproductive stages (40 and 70 days after planting; DAP). The (11)C-photoassimilate transport speed did not change over the two developmental stages. However, within a stem, transport speeds were reduced across nodes, likely due to higher (11)C-photoassimilate unloading in the nodes. Photosynthesis in leaves and the amount of (11)C that was exported to the rest of the plant decreased as plants matured. In young plants, exported (11)C was allocated mostly (88 %) to the roots and stem, but in flowering plants (70 DAP) the majority of the exported (11)C (64 %) was allocated to the apex. CONCLUSIONS: Our results show that commercial PET scanners can be used reliably to measure whole-plant C-allocation in large plants nondestructively including, importantly, allocation to roots in soil. This capability revealed extreme changes in carbon allocation in sorghum plants, as they advanced to maturity. Further, our results suggest that nodes may be important control points for photoassimilate distribution in crops of the family Poaceae. Quantifying real-time carbon allocation and photoassimilate transport dynamics, as demonstrated here, will be important for functional genomic studies to unravel the mechanisms controlling phloem transport in large crop plants, which will provide crucial insights for improving yields.

Investigation of SN2 [11C]cyanation for base-sensitive substrates: an improved radiosynthesis of L-[5-11C]-glutamine.

Carbon-11 (ß(+) emitter, t1/2 = 20.4 min) radiolabeled L-glutamine is a potentially useful molecular imaging agent that can be utilized with positron emission tomography for both human oncological diagnosis and plant imaging research. Based upon a previously reported [(11)C]cyanide end-capping labeling method, a systematic investigation of nucleophilic cyanation reactions and acidic hydrolysis reaction parameters, including base, metal ion source, phase transfer catalyst, solvent, reaction temperature and reaction time, was conducted. The result was a milder, more reliable, two-step method which provides L-[5-(11)C]-glutamine with a radiochemical yield of 63.8 ± 8.7% (range from 51 to 74%, n = 10) with >90% radiochemical purity and >90 % enantiomeric purity. The total synthesis time was 40-50 min from the end of bombardment. In addition, an Fmoc derivatization method was developed to measure the specific activity of this radiotracer.

An efficient and practical synthesis of [2-(11)C]indole via superfast nucleophilic [(11)C]cyanation and RANEY® Nickel catalyzed reductive cyclization.

A rapid method for the synthesis of carbon-11 radiolabeled indole was developed using a sub-nanomolar quantity of no-carrier-added [(11)C]cyanide as radio-precursor. Based upon a reported synthesis of 2-(2-nitrophenyl)acetonitrile (), a highly reactive substrate 2-nitrobenzyl bromide () was evaluated for nucleophilic [(11)C]cyanation. Additionally, related reaction conditions were explored with the goal of obtaining of highly reactive 2-(2-nitrophenyl)-[1-(11)C]acetonitrile () while inhibiting its rapid conversion to 2,3-bis(2-nitrophenyl)-[1-(11)C]propanenitrile (). Next, a RANEY® Nickel catalyzed reductive cyclization method was utilized for synthesizing the desired [2-(11)C]indole with hydrazinium monoformate as the active reducing agent. Extensive and iterative screening of basicity, temperature and stoichiometry was required to overcome the large stoichiometry bias that favored 2-nitrobenzylbromide () over [(11)C]cyanide, which both caused further alkylation of the desired nitrile and poisoned the RANEY® Nickel catalyst. The result is an efficient two-step, streamlined method to reliably synthesize [2-(11)C]indole with an entire radiochemical yield of 21 ± 2.2% (n = 5, ranging from 18-24%). The radiochemical purity of the final product was >98% and specific activity was 176 ± 24.8 GBq µmol(-1) (n = 5, ranging from 141-204 GBq µmol(-1)). The total radiosynthesis time including product purification by semi-preparative HPLC was 50-55 min from end of cyclotron bombardment.

Therapeutic doses of buspirone block D3 receptors in the living primate brain.

Dopamine D3 receptor (D3R) antagonists may be effective medications for multiple substance use disorders (SUDs). However, no selective D3R antagonists are currently available for clinical testing. Buspirone, originally characterized as a 5-HT1A partial agonist and used as an anxiolytic, also binds to D3R and D4R with high affinity, with lower affinity to D2R, and interferes with cocaine reward. Here we used PET with [11C]PHNO (D3R-preferring radioligand), [11C]raclopride (D2R/D3R radioligand) and [11C]NNC-112 (D1R radioligand) to measure occupancy of oral and parenteral buspirone in the primate brain. Intramuscular buspirone (0.19 and 0.5 mg/kg) blocked both [11C]PHNO and [11C]raclopride binding to striatum, exhibiting high occupancy (50-85%) at 15 min and rapid wash-out over 2-6 h. In contrast, oral buspirone (3 mg/kg) significantly blocked [11C]PHNO binding in D3-rich regions (globus pallidum and midbrain) at 3 h, but had minimal effects on [11C]raclopride binding (28-37% at 1 h and 10% at 3 h). Buspirone did not block [11C]NNC-112. Our findings provide evidence that i.m. buspirone blocks D3R and D2R, whereas oral buspirone is more selective towards D3R blockade in vivo, consistent with extensive first pass metabolism and supporting the hypothesis that its metabolites (5- and 6'-hydroxybuspirone) merit evaluation for treating SUDs. They also indicate that for oral buspirone to achieve greater than 80% sustained D3R occupancy, as might be needed to treat addiction, higher doses (at least three-fold) than those used to treat anxiety (maximal 60 mg) will be required. Nonetheless, based on previous clinical studies, these doses would be safe and well tolerated.

Positron Emission Tomography (PET) and Graphical Kinetic Data Analysis of the Dopamine Neurotransmitter System: An Exercise for an Undergraduate Laboratory Course.

Neuroimaging techniques, including positron emission tomography (PET), are widely used in clinical settings and in basic neuroscience research. Education in these methods and their applications may be incorporated into curricula to keep pace with this expanding field. Here, we have developed pedagogical materials on the fundamental principles of PET that incorporate a hands-on laboratory activity to view and analyze human brain scans. In this activity, students will use authentic PET brain scans generated from original research at Brookhaven National Laboratory (Volkow et al., 2009) to explore the neurobiological effects of a drug on the dopamine system. We provide lecture and assignment materials (including a 50-minute PowerPoint presentation introducing PET concepts), written background information for students and instructors, and explicit instructions for a 4-hour, computer-based laboratory to interested educators. Also, we discuss our experience implementing this exercise as part of an advanced undergraduate laboratory course at Stony Brook University in 2010 and 2011. Observing the living human brain is intriguing, and this laboratory is designed to illustrate how PET neuroimaging techniques are used to directly probe biological processes occurring in the living brain. Laboratory course modules on imaging techniques such as PET can pique the interest of students potentially interested in neuroscience careers, by exposing them to current research methods. This activity provides practical experience analyzing PET data using a graphical analysis method known as the Logan plot, and applies core neuropharmacology concepts. We hope that this manuscript inspires college instructors to incorporate education in PET neuroimaging into their courses.

Optimization and scale up of production of the PSMA imaging agent [18F]AlF-P16-093 on a custom automated radiosynthesis platform.

BACKGROUND: Recent advancements in positron emission tomograph (PET) using prostate specific membrane antigen (PSMA)-targeted radiopharmaceuticals have changed the standard of care for prostate cancer patients by providing more accurate information during staging of primary and recurrent disease. [68Ga]Ga-P16-093 is a new PSMA-PET radiopharmaceutical that demonstrated superior imaging performance in recent head-to-head studies with [68Ga]Ga-PSMA-11. To improve the availability of this new PSMA PET imaging agent, [18F]AlF-P16-093 was developed. The 18F-analog [18F]AlF-P16-093 has been synthesized manually at low activity levels using [18F]AlF2+ and validated in pre-clinical models. This work reports the optimization of the production of > 15 GBq of [18F]AlF-P16-093 using a custom automated synthesis platform. RESULTS: The sensitivity of the radiochemical yield of [18F]AlF-P16-093 to reaction parameters of time, temperature and reagent amounts was investigated using a custom automated system. The automated system is a low-cost, cassette-based system designed for 1-pot syntheses with flow-controlled solid phase extraction (SPE) workup and is based on the Raspberry Pi Zero 2 microcomputer/Python3 ecosystem. The optimized none-decay-corrected yield was 52 ± 4% (N = 3; 17.5 ± 2.2 GBq) with a molar activity of 109 ± 14 GBq/µmole and a radiochemical purity of 98.6 ± 0.6%. Run time was 30 min. A two-step sequence was used: SPE-purified [18F]F- was reacted with 80 nmoles of freeze-dried AlCl3·6H2O at 65 °C for 5 min followed by reaction with 160 nmoles of P16-093 ligand at 40 °C for 4 min in a 1:1 mixture of ethanol:0.5 M pH 4.5 NaOAc buffer. The mixture was purified by SPE (> 97% recovery). The final product formulation (5 mM pH 7 phosphate buffer with saline) exhibited a rate of decline in radiochemical purity of ~ 1.4%/h which was slowed to ~ 0.4%/h when stored at 4 °C. CONCLUSION: The optimized method using a custom automated system enabled the efficient (> 50% none-decay-corrected yield) production of [18F]AlF-P16-093 with high radiochemical purity (> 95%). The method and automation system are simple and robust, facilitating further clinical studies with [18F]AlF-P16-093.

Theranostic Agent Targeting Bone Metastasis: A Novel [68Ga]Ga/[177Lu]Lu-DOTA-HBED-bisphosphonate.

Bone metastasis in cancer patients is a major disease advancement for various types of cancer. Previously, [68Ga]Ga-HBED-CC-bisphosphonate ([68Ga]Ga-P15-041) showed excellent bone uptake and efficient detection of bone metastasis in patients. To accommodate different α- or ß--emitting metals for radionuclide therapy, a novel DOTA-HBED-CC-bisphosphonate (P15-073, 1) was prepared and the corresponding [68Ga]Ga-1 and [177Lu]Lu-1 were successfully synthesized in high yields and purity. Gallium-68 conjugation to HBED-CC at room temperature and lutetium-177 conjugation to DOTA at 95 °C were verified in model compounds through secondary mass confirmation. These bisphosphonates, [68Ga]Ga-1 and [177Lu]Lu-1, displayed high binding affinity to hydroxyapatite in vitro. After an iv injection, it showed excellent uptake in the spine of normal mice, and micro-PET/CT imaging of nude mice model of bone metastasis showed high bone uptake in tumor tissue. The results indicated that [68Ga]Ga/[177Lu]Lu-1 holds promise as a theranostic radioligand agent for managing cancer bone metastases.

Acute alcohol intoxication decreases glucose metabolism but increases acetate uptake in the human brain.

Alcohol intoxication results in marked reductions in brain glucose metabolism, which we hypothesized reflect not just its GABAergic enhancing effects but also the metabolism of acetate as an alternative brain energy source. To test this hypothesis we separately assessed the effects of alcohol intoxication on brain glucose and acetate metabolism using Positron Emission Tomography (PET). We found that alcohol intoxication significantly decreased whole brain glucose metabolism (measured with FDG) with the largest decrements in cerebellum and occipital cortex and the smallest in the thalamus. In contrast, alcohol intoxication caused a significant increase in [1-(11)C]acetate brain uptake (measured as standard uptake value, SUV), with the largest increases occurring in the cerebellum and the smallest in the thalamus. In heavy alcohol drinkers [1-(11)C]acetate brain uptake during alcohol challenge tended to be higher than in occasional drinkers (p<0.06) and the increases in [1-(11)C]acetate uptake in cerebellum with alcohol were positively associated with the reported amount of alcohol consumed (r=0.66, p<0.01). Our findings corroborate a reduction of brain glucose metabolism during intoxication and document an increase in brain acetate uptake. The opposite changes observed between regional brain metabolic decrements and regional increases in [1-(11)C]acetate uptake support the hypothesis that during alcohol intoxication the brain may rely on acetate as an alternative brain energy source and provides preliminary evidence that heavy alcohol exposures may facilitate the use of acetate as an energy substrate. These findings raise the question of the potential therapeutic benefits that increasing plasma acetate concentration (i.e. ketogenic diets) may have in alcoholics undergoing alcohol detoxification.

In vivo imaging of brain aromatase in female baboons: [11C]vorozole kinetics and effect of the menstrual cycle.

The aim of this work was to quantify the brain distribution of the enzyme aromatase in the female baboon with positron emission tomography and the tracer [11C]vorozole using three different quantification methods for estimating the total distribution volume (V(T)): a graphical method, compartment modeling, and a tissue to plasma ratio. The graphical model and the compartment modeling gave similar estimates to the data and similar values (correlation R  =  .988; p  =  .0001). [11C]Vorozole shows a rapid uptake by the brain followed by a relatively constant accumulation, suggesting the possibility of using the tissue to plasma ratio as an estimate of V(T). The highest uptake of [11C]vorozole in the baboon brain was measured in the amygdala, followed by the preoptic area and hypothalamus, basal ganglia, and cortical areas. Pretreatment studies with vorozole or letrozole showed a generalized decrease in brain accumulation and V(T). The results suggested that the physiologic changes in gonadal hormone levels accompanying the menstrual cycle had a significant effect on brain aromatase V(T).