scholarly journals Improved in vivo PET imaging of the adenosine A2A receptor in the brain using [18F]FLUDA, a deuterated radiotracer with high metabolic stability

2021 ◽  
Author(s):  
Thu Hang Lai ◽  
Magali Toussaint ◽  
Rodrigo Teodoro ◽  
Sladjana Dukić-Stefanović ◽  
Daniel Gündel ◽  
...  
Keyword(s):  
Specific Binding ◽  
Radiochemical Yield ◽  
Toxicity Study ◽  
In Vivo Evaluation ◽  
One Pot ◽  
Specific Binding Ratio ◽  
Mri Studies ◽  
The Brain

Abstract Purpose The adenosine A2A receptor has emerged as a therapeutic target for multiple diseases, and thus the non-invasive imaging of the expression or occupancy of the A2A receptor has potential to contribute to diagnosis and drug development. We aimed at the development of a metabolically stable A2A receptor radiotracer and report herein the preclinical evaluation of [18F]FLUDA, a deuterated isotopologue of [18F]FESCH. Methods [18F]FLUDA was synthesized by a two-step one-pot approach and evaluated in vitro by autoradiographic studies as well as in vivo by metabolism and dynamic PET/MRI studies in mice and piglets under baseline and blocking conditions. A single-dose toxicity study was performed in rats. Results [18F]FLUDA was obtained with a radiochemical yield of 19% and molar activities of 72–180 GBq/μmol. Autoradiography proved A2A receptor–specific accumulation of [18F]FLUDA in the striatum of a mouse and pig brain. In vivo evaluation in mice revealed improved stability of [18F]FLUDA compared to that of [18F]FESCH, resulting in the absence of brain-penetrant radiometabolites. Furthermore, the radiometabolites detected in piglets are expected to have a low tendency for brain penetration. PET/MRI studies confirmed high specific binding of [18F]FLUDA towards striatal A2A receptor with a maximum specific-to-non-specific binding ratio in mice of 8.3. The toxicity study revealed no adverse effects of FLUDA up to 30 μg/kg, ~ 4000-fold the dose applied in human PET studies using [18F]FLUDA. Conclusions The new radiotracer [18F]FLUDA is suitable to detect the availability of the A2A receptor in the brain with high target specificity. It is regarded ready for human application.

68Ga-labeled HBED-CC Variant of uPAR Targeting Peptide AE105 Compared with 68Ga-NODAGA-AE105

2019 ◽  
Vol 18 (9) ◽  
pp. 1289-1294 ◽  
Author(s):  
Kusum Vats ◽  
Rohit Sharma ◽  
Haladhar D. Sarma ◽  
Drishty Satpati ◽  
Ashutosh Dash
Keyword(s):  
Solid Phase ◽  
Evaluation Studies ◽  
Radiochemical Yield ◽  
In Vivo Evaluation ◽  
Peptide Conjugates ◽  
Biodistribution Studies ◽  
Target Organs ◽  
U87mg Tumor

Aims: The urokinase Plasminogen Activator Receptors (uPAR) over-expressed on tumor cells and their invasive microenvironment are clinically significant molecular targets for cancer research. uPARexpressing cancerous lesions can be suitably identified and their progression can be monitored with radiolabeled uPAR targeted imaging probes. Hence this study aimed at preparing and evaluating two 68Ga-labeled AE105 peptide conjugates, 68Ga-NODAGA-AE105 and 68Ga-HBED-CC-AE105 as uPAR PET-probes. Method: The peptide conjugates, HBED-CC-AE105-NH2 and NODAGA-AE105-NH2 were manually synthesized by standard Fmoc solid phase strategy and subsequently radiolabeled with 68Ga eluted from a commercial 68Ge/68Ga generator. In vitro cell studies for the two radiotracers were performed with uPAR positive U87MG cells. Biodistribution studies were carried out in mouse xenografts with the subcutaneously induced U87MG tumor. Results: The two radiotracers, 68Ga-NODAGA-AE105 and 68Ga-HBED-CC-AE105 that were prepared in >95% radiochemical yield and >96% radiochemical purity, exhibited excellent in vitro stability. In vivo evaluation studies revealed higher uptake of 68Ga-HBED-CC-AE105 in U87MG tumor as compared to 68Ga-NODAGAAE105; however, increased lipophilicity of 68Ga-HBED-CC-AE105 resulted in slower clearance from blood and other non-target organs. The uPAR specificity of the two radiotracers was ascertained by significant (p<0.05) reduction in the tumor uptake with a co-injected blocking dose of unlabeled AE-105 peptide. Conclusion: Amongst the two radiotracers studied, the neutral 68Ga-NODAGA-AE105 with more hydrophilic chelator exhibited faster clearance from non-target organs. The conjugation of HBED-CC chelator (less hydrophilic) resulted in negatively charged 68Ga-HBED-CC-AE105 which was observed to have high retention in blood that decreased target to non-target ratios.

scholarly journals Preclinical characterization of [18F]T-008, a novel PET imaging radioligand for cholesterol 24-hydroxylase

2021 ◽  
Author(s):  
Tatsuki Koike ◽  
Cristian C. Constantinescu ◽  
Shuhei Ikeda ◽  
Toshiya Nishi ◽  
Eiji Sunahara ◽  
...  
Keyword(s):  
Mouse Brain ◽  
Pet Imaging ◽  
Rank Order ◽  
Cholesterol Homeostasis ◽  
Dependent Manner ◽  
Wild Type ◽  
In Vivo Evaluation ◽  
The Brain

Abstract Purpose Cholesterol 24-hydroxylase (CH24H) is a brain-specific enzyme that plays a major role in brain cholesterol homeostasis by converting cholesterol into 24S-hydroxycholesterol. The selective CH24H inhibitor soticlestat (TAK-935) is being pursued as a drug for treatment of seizures in developmental and epileptic encephalopathies. Herein, we describe the successful discovery and the preclinical validation of the novel radiolabeled CH24H ligand (3-[18F]fluoroazetidin-1-yl){1-[4-(4-fluorophenyl)pyrimidin-5-yl]piperidin-4-yl}methanone ([18F]T-008) and its tritiated analog, [3H]T-008. Methods In vitro autoradiography (ARG) studies in the CH24H wild-type (WT) and knockout (KO) mouse brain sections were conducted using [3H]T-008. PET imaging was conducted in two adult rhesus macaques using [18F]T-008. Each macaque received two test–retest baseline scans and a series of two blocking doses of soticlestat administered prior to [18F]T-008 to determine the CH24H enzyme occupancy. PET data were analyzed with Logan graphical analysis using plasma input. A Lassen plot was applied to estimate CH24H enzyme occupancy by soticlestat. Results In ARG studies, binding of [3H]T-008 was specific to CH24H in the mouse brain sections, which was not observed in CH24H KO or in wild-type mice after pretreatment with soticlestat. In rhesus PET studies, the rank order of [18F]T-008 uptake was striatum > cortical regions > cerebellum, which was consistent with CH24H distribution in the brain. Pre-blocking with soticlestat reduced the maximum uptake and increased the washout in all brain regions in a dose-dependent manner. Calculated global occupancy values for soticlestat at a dose of 0.89 mg/kg were 97–98%, indicating maximum occupancy. Conclusion The preclinical in vitro and in vivo evaluation of labeled T-008 demonstrates that [18F]T-008 is suitable for imaging CH24H in the brain and warrants further studies in humans. Graphical abstract

scholarly journals Encapsulated Escitalopram and Paroxetine Intranasal Co-Administration: In Vitro/In Vivo Evaluation

2021 ◽  
Vol 12 ◽  
Author(s):  
Soraia Silva ◽  
Joana Bicker ◽  
Carla Fonseca ◽  
Nuno R. Ferreira ◽  
Carla Vitorino ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Selective Serotonin Reuptake Inhibitors ◽  
Common Mental Disorder ◽  
Drug Loading ◽  
Pharmacokinetic Studies ◽  
Brain Delivery ◽  
In Vivo Evaluation ◽  
The Brain

Depression is a common mental disorder. Its treatment with selective serotonin reuptake inhibitors (SSRIs) is effective only in a fraction of patients, and pharmacoresistance is increasing steadily. Intranasal (IN) drug delivery to the brain stands out as a promising strategy to improve current therapeutic approaches by operating as a shuttle to overcome the blood–brain barrier. This work aimed to simultaneously administer escitalopram and paroxetine by IN route to mice. For this purpose, three nanostructured lipid carriers (NLC1, NLC2, and BorNLC) and one nanoemulsion (NE) were tested for drug loading. After their characterization, investigation of their impact on nasal cell viability and SSRI permeability assays were performed, using a human nasal RPMI 2650 cell line in air–liquid interface. In vitro assays demonstrated that NLCs, including borneol (BorNLC), significantly increased escitalopram permeability (p &lt; 0.01) and paroxetine recovery values (p &lt; 0.05) in relation to the other formulations and non-encapsulated drugs. IN and intravenous (IV) pharmacokinetic studies performed in vivo with a single dose of 2.38 mg/kg demonstrated similar results for escitalopram brain-to-plasma ratios. IN administrations delayed escitalopram peak concentrations in the brain for 15–60 min and no direct nose-to-brain delivery was detected. However, encapsulation with BorNLC considerably decreased escitalopram exposure in the lungs (124 μg min/g) compared with free escitalopram by IN (168 μg min/g) and IV (321 μg min/g) routes. Surprisingly, BorNLC IN instillation increased concentration levels of paroxetine in the brain by five times and accelerated brain drug delivery. Once again, lung exposure was considerably lower with BorNLC (AUCt = 0.433 μg min/g) than that with IV administration (AUCt = 1.01 μg min/g) and non-encapsulated IN formulation (AUCt = 2.82 μg min/g). Direct nose-to-brain delivery was observed for paroxetine IN administration with a direct transport percentage (DTP) of 56.9%. If encapsulated, it increases to 74.2%. These results clearly emphasize that nose-to-brain delivery and lung exposure depend on the formulation and on the characteristics of the drug under investigation. NLCs seem to be an advantageous strategy for nose-to-brain delivery of lipophilic molecules, since they reduce systemic and lung exposure, thereby decreasing adverse effects. For hydrophilic compounds, NLCs are particularly important to decrease lung exposure after IN administration.

In vitro and in vivo Evaluation of the Radiochemical Compound Based on 99mTechnetium Labelled DARPin 9_29 for Molecular Visualization of Malignancies Overexpressing Her2/neu

2020 ◽  
Vol 65 (1) ◽  
pp. 37-41
Author(s):  
O. Bragina ◽  
A. Vorobyeva ◽  
V. Tolmachev ◽  
A. Orlova ◽  
V. Chernov ◽  
...  
Keyword(s):  
In Vitro Study ◽  
Radiochemical Yield ◽  
Blood Stream ◽  
The Body ◽  
Diagnostic Methods ◽  
In Vivo Studies ◽  
In Vivo Evaluation ◽  
High Accumulation

Purpose: Evaluation of a radiopharmaceutical based on 99mTc-labeled targeted molecules DARPin9_29 for radionuclide diagnostics of malignancies with Her2/neu overexpression. Material and methods: The DARPin9_29 sequence was amplified from the plasmid pET-DARP-6HIS for the DARPin9_29-His6 gene expression in E. coli cells. The eluent of 99mTcO4– (400–500 μl, 4 GBq) was added to the kit and incubated at a temperature of 100 °C for 20 minutes. After incubation, 40 μl of tricarbonyl technetium was added to 168 μg of DARPin9_29 in 100 μl of PBS (sodium phosphate buffer), followed by incubation at 40 °C for 60 minutes. The radiochemical yield and purity were determined by thin layer radiochromatography, the purification was performed using NAP-5 cleansing columns (GE Healthcare). Cell lines with different levels of Her2/neu expression were used: SKOV-3> BT474 >> DU-145 for the determination of the radiopharmaceutical specificity. Her2/neu expressing cell line SKOV-3 was used for in vitro study. The study was conducted 6 hours after the administration of the drug. Results: The radiochemical yield was 72 ± 8 %, the radiochemical purity after purification was 98.7 ± 1.0 %. The stability in PBS (phosphate buffered saline) solution after 1 hour was 99.8 ± 0.2; after 3 hours – 98.2 ± 0.1. In vitro studies showed that the accumulation of explored compound was directly proportional to the level of Her2/neu expression in cells, while blocking the receptors with an excess of unlabeled protein showed a significant reduction in binding in the group of cells. Data on biodistribution and SPECT/CT in the body of the animal BALB/c nu/nu demonstrated rapid removal of the compound from the blood stream and high accumulation in the liver, kidney and bladder 6 hours after the introduction of the radiopharmaceutical. Conclusion: The studies demonstrated high radiochemical yields and purity, as well as stability of the studied compound. The results of in vitro and in vivo analysis showed the specificity and affinity of the radiopharmaceutical to the Her2/neu receptor on the surface of tumor cells. The high accumulation of the drug in the liver and kidneys, detected in in vivo studies, is probably due to the lipophilicity of the 99mTc(CO)3-histidine tag and indicates the limitation of its further clinical use in assessing the condition of the above organs, which will require additional diagnostic methods, as well as possible modification chemical structure.

High non-specific binding of the β1-selective radioligand 2-125I-ICI-H

2003 ◽  
Vol 42 (04) ◽  
pp. 173-180 ◽  
Author(s):  
M. P. Law ◽  
K. Kopka ◽  
St. Wagner ◽  
S. Luthra ◽  
V. W. Pike ◽  
...  
Keyword(s):  
Specific Activity ◽  
Single Photon ◽  
Specific Binding ◽  
Photon Emission ◽  
Radiochemical Yield ◽  
Emission Computed Tomography ◽  
Biodistribution Studies ◽  
Positron Emission

Summary: Aim: As results of cardiac biopsies suggest, myocardial β1-adrenoceptor density is reduced in patients with chronic heart failure. However, changes in cardiac β2-adrenoceptors vary. With suitable radiopharmaceuticals single photon emission computed tomography (SPECT) and positron emission tomography (PET) offer the opportunity to assess β-adrenoceptors non-invasively. Among the novel racemic analogues of the established β1-selective adrenoceptor antagonist ICI 89.406 the iodinated 2-I-ICI-H showed high affinity and selectivity to β1-adrenoceptors in murine ventricular membranes. The aim of this study was its evaluation as a putative sub-type selective β1-adrenergic radioligand in cardiac imaging. Methods: Competition studies in vitro and in vivo were used to investigate the kinetics of 2-I-ICI-H binding to cardiac β-adrenoceptors in mice and rats. In addition, the radiosynthesis of 2-125I-ICI-H from the silylated precursor 2-SiMe3-ICI-H was established. The specific activity was 80 GBq/µmol, the radiochemical yield ranged from 70 to 80%. Results: The unlabelled compound 2-I-ICI-H showed high β1-selectivity and -affinity in the in vitro competition studies. In vivo biodistribution studies apparently showed low affinity to cardiac β-adrenoceptors. The radiolabelled counterpart 2-125I-ICI-H showed a high degree of non-specific binding in vitro and no specific binding to cardiac β1-adrenoceptors in vivo. Conclusion: Because of its high non-specific binding 2-125I-ICI-H is no suitable radiotracer for imaging in vivo.

scholarly journals Automated GMP-Compliant Production of [68Ga]Ga-DO3A-Tuna-2 for PET Microdosing Studies of the Glucagon Receptor in Humans

2020 ◽  
Vol 13 (8) ◽  
pp. 176
Author(s):  
Michael Wagner ◽  
Johan G. Doverfjord ◽  
Joachim Tillner ◽  
Gunnar Antoni ◽  
Torsten Haack ◽  
...  
Keyword(s):  
Manufacturing Process ◽  
Specific Binding ◽  
Radiochemical Yield ◽  
Radical Scavenger ◽  
Glucagon Receptor ◽  
Residual Solvent ◽  
Process Validation ◽  
Integrity Tests

Introduction: [68Ga]Ga-DO3A-VS-Cys40-Tuna-2 (previously published as [68Ga]Ga-DO3A-VS-Cys40-S01-GCG) has shown high-affinity specific binding to the glucagon receptor (GCGR) in vitro and in vivo in rats and non-human primates in our previous studies, confirming the suitability of the tracer for drug development applications in humans. The manufacturing process of [68Ga]Ga-DO3A-VS-Cys40-Tuna-2 was automated for clinical use to meet the radiation safety and good manufacturing practice (GMP) requirements. Methods: The automated synthesis platform (Modular-Lab PharmTrace, Eckert & Ziegler, Eurotope, Germany), disposable cassettes for 68Ga-labeling, and pharmaceutical-grade 68Ge/68Ga generator (GalliaPharm®) used in the study were purchased from Eckert & Ziegler. The parameters such as time, temperature, precursor concentration, radical scavenger, buffer concentration, and pH, as well as product purification step, were investigated and optimized. Process optimization was conducted with regard to product quality and quantity, as well as process reproducibility. The active pharmaceutical ingredient starting material DO3A-VS-Cys40-Tuna-2 (GMP-grade) was provided by Sanofi Aventis. Results: The reproducible and GMP-compliant automated production of [68Ga]Ga-DO3A-VS-Cys40-Tuna-2 with on-line documentation was developed. The non-decay-corrected radiochemical yield was 45.2 ± 2.5% (n = 3, process validation) at the end of the synthesis with a labeling synthesis duration of 38 min and a quality controlincluding release procedure of 20 min. The radiochemical purity of the product was 98.9 ± 0.6% (n = 17) with the total amount of the peptide in the preparation of 48 ± 2 µg (n = 3, process validation). Radionuclidic purity, sterility, endotoxin content, residual solvent content, and sterile filter integrity tests met the acceptance criteria. The product was stable at ambient temperature for at least 2 h. Conclusion: The fully automated GMP-compliant manufacturing process was developed and thoroughly validated. The resulting [68Ga]Ga-DO3A-VS-Cys40-Tuna-2 was used in a clinical study for accurate quantification of GCGR occupancy by a dual anti-diabetic drug in vivo in humans.

scholarly journals Radiosynthesis and Biological Investigation of a Novel Fluorine-18 Labeled Benzoimidazotriazine- Based Radioligand for the Imaging of Phosphodiesterase 2A with Positron Emission Tomography

Molecules ◽  
2019 ◽  
Vol 24 (22) ◽  
pp. 4149
Author(s):  
Ritawidya ◽  
Wenzel ◽  
Teodoro ◽  
Toussaint ◽  
Kranz ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Specific Binding ◽  
Standardized Uptake Value ◽  
Radiochemical Yield ◽  
Biological Evaluation ◽  
Emission Tomography ◽  
Biological Investigation ◽  
Positron Emission

A specific radioligand for the imaging of cyclic nucleotide phosphodiesterase 2A (PDE2A) via positron emission tomography (PET) would be helpful for research on the physiology and disease-related changes in the expression of this enzyme in the brain. In this report, the radiosynthesis of a novel PDE2A radioligand and the subsequent biological evaluation were described. Our prospective compound 1-(2-chloro-5-methoxy phenyl)-8-(2-fluoropyridin-4-yl)-3- methylbenzo[e]imidazo[5,1-c][1,2,4]triazine, benzoimidazotriazine (BIT1) (IC50 PDE2A = 3.33 nM; 16-fold selectivity over PDE10A) was fluorine-18 labeled via aromatic nucleophilic substitution of the corresponding nitro precursor using the K[18F]F‐K2.2.2‐carbonate complex system. The new radioligand [18F]BIT1 was obtained with a high radiochemical yield (54 ± 2%, n = 3), a high radiochemical purity (≥99%), and high molar activities (155–175 GBq/μmol, n = 3). In vitro autoradiography on pig brain cryosections exhibited a heterogeneous spatial distribution of [18F]BIT1 corresponding to the known pattern of expression of PDE2A. The investigation of in vivo metabolism of [18F]BIT1 in a mouse revealed sufficient metabolic stability. PET studies in mouse exhibited a moderate brain uptake of [18F]BIT1 with a maximum standardized uptake value of ~0.7 at 5 minutes p.i. However, in vivo blocking studies revealed a non-target specific binding of [18F]BIT1. Therefore, further structural modifications are needed to improve target selectivity.

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