Cardiac PET Imaging of ATP Binding Cassette (ABC) Transporters: Opportunities and Challenges

Adenosine triphosphate binding cassette (ABC) transporters are a broad family of membrane protein complexes that use energy to transport molecules across cells and/or intracellular organelle lipid membranes. Many drugs used to treat cardiac diseases have an affinity for these transporters. Among others, P-glycoprotein (P-gp) plays an essential role in regulating drug concentrations that reach cardiac tissue and therefore contribute to cardiotoxicity. As a molecular imaging modality, positron emission tomography (PET) has emerged as a viable technique to investigate the function of P-gp in organs and tissues. Using PET imaging to evaluate cardiac P-gp function provides new insights for drug development and improves the precise use of medications. Nevertheless, information in this field is limited. In this review, we aim to examine the current applications of ABC transporter PET imaging and its tracers in the heart, with a specific emphasis on P-gp. Furthermore, the opportunities and challenges in this novel field will be discussed.

Quantification of P-glycoprotein function at the human blood-brain barrier using [18F]MC225 and PET

INTRODUCTION

P-glycoprotein (P-gp) is one of the most studied efflux transporters at the blood-brain barrier. It plays an important role in brain homeostasis by protecting the brain from a variety of endogenous and exogeneous substances. Changes in P-gp function are associated both with the onset of neuropsychiatric diseases, including Alzheimer's disease and Parkinson's disease, and with drug-resistance, for example in treatment-resistant depression. The most widely used approach to measure P-gp function in vivo is (R)-[11C]verapamil PET. (R)-[11C]verapamil is, however, an avid P-gp substrate, which complicates the use of this tracer to measure an increase in P-gp function as its baseline uptake is already very low. [18F]MC225 was developed to measure both increases and decreases in P-gp function.

AIM

The aim of this study was (1) to identify the pharmacokinetic model that best describes [18F]MC225 kinetics in the human brain and (2) to determine test-retest variability.

METHODS

Five (2 male, 3 female) of fourteen healthy subjects (8 male, 6 female, age 67 ± 5 years) were scanned twice (injected dose 201 ± 47 MBq) with a minimum interval of 2 weeks between scans. Each scanning session consisted of a 60-min dynamic [18F]MC225 scan with continuous arterial sampling. Whole brain grey matter data were fitted to a single tissue compartment model, and to reversible and irreversible two tissue-compartment models to obtain various outcome parameters (in particular the volume of distribution (VT), Ki, and the rate constants K1 and k2). In addition, a reversible two-tissue compartment model with fixed k3/k4 was included. The preferred model was selected based on the weighted Akaike Information Criterion (AIC) score. Test-retest variability (TRTV) was determined to assess reproducibility.

RESULTS

Sixty minutes post-injection, the parent fraction was 63.8 ± 4.0%. The reversible two tissue compartment model corrected for plasma metabolites with an estimated blood volume (VB) showed the highest AIC weight score of 34.3 ± 17.6%. The TRVT of the VT for [18F]MC225 PET scans was 28.3 ± 20.4% for the whole brain grey matter region using this preferred model.

CONCLUSION

[18F]MC225 VT, derived using a reversible two-tissue compartment model, is the preferred parameter to describe P-gp function in the human BBB. This outcome parameter has an average test-retest variability of 28%.

TRIAL REGISTRATION

EudraCT 2020-001564-28 . Registered 25 May 2020.

Effects of proton therapy on regional [18F]FDG uptake in non-tumor brain regions of patients treated for head and neck cancer

Background and purpose

Previous pre-clinical research using [¹⁸F]FDG-PET has shown that whole-brain photon-based radiotherapy can affect brain glucose metabolism. This study, aimed to investigate how these findings translate into regional changes in brain [¹⁸F]FDG uptake in patients with head and neck cancer treated with intensity-modulated proton therapy (IMPT).

Materials and methods

Twenty-three head and neck cancer patients treated with IMPT and available [¹⁸F]FDG scans before and at 3 months follow-up were retrospectively evaluated. Regional assessment of the [¹⁸F]FDG standardized uptake value (SUV) parameters and radiation dose in the left (L) and right (R) hippocampi, L and R occipital lobes, cerebellum, temporal lobe, L and R parietal lobes and frontal lobe were evaluated to understand the relationship between regional changes in SUV metrics and radiation dose.

Results

Three months after IMPT, [¹⁸F]FDG brain uptake calculated using SUVmean and SUVmax, was significantly higher than that before IMPT. The absolute SUVmean after IMPT was significantly higher than before IMPT in seven regions of the brain (p ≤ 0.01), except for the R (p = 0.11) and L (p = 0.15) hippocampi. Absolute and relative changes were variably correlated with the regional maximum and mean doses received in most of the brain regions.

Conclusion

Our findings suggest that 3 months after completion of IMPT for head and neck cancer, significant increases in the uptake of [¹⁸F]FDG (reflected by SUVmean and SUVmax) can be detected in several individual key brain regions, and when evaluated jointly, it shows a negative correlation with the mean dose. Future studies are needed to assess whether and how these results could be used for the early identification of patients at risk for adverse cognitive effects of radiation doses in non-tumor tissues.

[15O]H2O PET: Potential or Essential for Molecular Imaging?

Imaging water pathways in the human body provides an excellent way of measuring accurately the blood flow directed to different organs. This makes it a powerful diagnostic tool for a wide range of diseases that are related to perfusion and oxygenation. Although water PET has a long history, its true potential has not made it into regular clinical practice. The article highlights the potential of water PET in molecular imaging and suggests its prospective role in becoming an essential tool for the 21st century precision medicine in different domains ranging from preclinical to clinical research and practice. The recent technical advances in high-sensitivity PET imaging can play a key accelerating role in empowering this technique, though there are still several challenges to overcome.

Severely increased albuminuria in patients with type 2 diabetes mellitus is associated with increased subclinical atherosclerosis in femoral arteries with Na [18F]F activity as a proxy - The DETERMINE study

BACKGROUND AND AIMS

Sodium [18F]fluoride (Na [18F]F) positron emission tomography imaging allows detailed visualization of early arterial micro-calcifications. This study aims to investigate atherosclerosis manifested by micro-calcification, macro-calcification, and aortic stiffness in patients with type 2 diabetes mellitus (T2DM) with and without albuminuria and severely decreased kidney function.

METHODS

A cohort was stratified in four groups (N = 10 per group), based on KDIGO categories (G1-5 A1-3). G1-2A1 non-diabetic controls (median [IQR] estimated glomerular filtration rate (eGFR) in mL/min/1.73 m2 91 [81-104]), G1-2A1 with T2DM (eGFR 87 [84-93], and albumin-creatinin-ratio (ACR) in mg/mmol 0.35 [0.25-0.75]), G1-2A3 with T2DM (eGFR 85 [60-103], and ACR 74 [62-122], and G4A3 with T2DM (eGFR 19 [13-27] and ACR 131 [59-304]).

RESULTS

Na [18F]F femoral artery grading score differed significantly in the groups with the highest Na [18F]F activity in A3 groups with T2DM (G1-2A3 with T2DM 228 [100-446] and G4A3 with T2DM 198 [113-578]) from the lowest groups of the G1-2A1 with T2DM (33 [0-93]) and in G1-2A1 non-diabetic controls (75 [0-200], p = 0.001). Aortic Na [18F]F activity and femoral artery computed tomography (CT)-assessed macro-calcification was increased in G4A3 with T2DM compared with G1-2A1 with T2DM (47.5 [33.8-73.8] vs. 17.5 [8.8-27.5] (p = 0.006) and 291 [170-511] vs. 12.2 [1.41-44.3] mg (p = 0.032), respectively). Carotid-femoral pulse wave velocity (PWV)-assessed aortic stiffness was significantly higher in both A3 groups with T2DM compared with G1-2A1 with T2DM (11.15 and 12.35 vs. 8.86 m/s, respectively (p = 0.009)).

CONCLUSIONS

This study indicates that the presence of severely increased albuminuria in patients with T2DM is cross-sectionally associated with subclinical arterial disease in terms of micro-calcification and aortic stiffness. Additional decrease in kidney function was associated with advanced macro-calcifications.

Oral administration of PET tracers: Current status

The oral route is the most widely used and preferable way of drug administration. Several pharmacokinetic processes play a role in the distribution of administered drugs. Therefore, accurate quantification of absorption, distribution, metabolism, excretion, and characterisation of drug kinetics after oral administration is extremely important for developing new human drugs. In vivo methods, such as gamma-scintigraphy, magnetic resonance imaging (MRI), and positron emission tomography (PET), have been used to analyse gastrointestinal tract (GIT) absorption behaviour. This scoping review provides an overview of PET studies that used oral tracer administration. A systematic literature search was performed using PubMed, EMBASE, Scopus, Science Direct, and Web of Science databases. Extensive variation between these studies was seen concerning acquisition protocols, quantification methods, and pharmacokinetic outcome parameters. Studies in humans indicate that it takes 10 to 30 min for the tracer to be in the intestine and about 100 min to reach its maximum concentration in the brain. In rodent studies, different pharmacokinetic parameters for the brain, blood, and GIT were estimated, showing the potential of PET to measure the absorption and distribution of drugs and pharmaceuticals non-invasively. Finally, regarding radiation protection, oral administration has a higher absorbed dose in GIT and, consequently, a higher effective dose. However, with the recent introduction of Long Axial Field of View (LAFOV) PET scanners, it is possible to reduce the administered dose, making oral administration feasible for routine clinical studies.

Non-invasive kinetic modelling approaches for quantitative analysis of brain PET studies

Pharmacokinetic modelling with arterial sampling is the gold standard for analysing dynamic PET data of the brain. However, the invasive character of arterial sampling prevents its widespread clinical application. Several methods have been developed to avoid arterial sampling, in particular reference region methods. Unfortunately, for some tracers or diseases, no suitable reference region can be defined. For these cases, other potentially non-invasive approaches have been proposed: (1) a population based input function (PBIF), (2) an image derived input function (IDIF), or (3) simultaneous estimation of the input function (SIME). This systematic review aims to assess the correspondence of these non-invasive methods with the gold standard. Studies comparing non-invasive pharmacokinetic modelling methods with the current gold standard methods using an input function derived from arterial blood samples were retrieved from PubMed/MEDLINE (until December 2021). Correlation measurements were extracted from the studies. The search yielded 30 studies that correlated outcome parameters (V_T, DVR, or BP_ND for reversible tracers; K_i or CMR_glu for irreversible tracers) from a potentially non-invasive method with those obtained from modelling using an arterial input function. Some studies provided similar results for PBIF, IDIF, and SIME-based methods as for modelling with an arterial input function (R² = 0.59-1.00, R² = 0.71-1.00, R² = 0.56-0.96, respectively), if the non-invasive input curve was calibrated with arterial blood samples. Even when the non-invasive input curve was calibrated with venous blood samples or when no calibration was applied, moderate to good correlations were reported, especially for the IDIF and SIME (R² = 0.71-1.00 and R² = 0.36-0.96, respectively). Overall, this systematic review illustrates that non-invasive methods to generate an input function are still in their infancy. Yet, IDIF and SIME performed well, not only with arterial blood calibration, but also with venous or no blood calibration, especially for some tracers without plasma metabolites, which would potentially make these methods better suited for clinical application. However, these methods should still be properly validated for each individual tracer and application before implementation.

A proof-of-concept study on the use of a fluorescein-based 18F-tracer for pretargeted PET

Background

Pretargeted immuno-PET tumor imaging has emerged as a valuable diagnostic strategy that combines the high specificity of antibody-antigen interaction with the high signal and image resolution offered by short-lived PET isotopes, while reducing the irradiation dose caused by traditional ⁸⁹Zr-labelled antibodies. In this work, we demonstrate proof of concept of a novel ‘two-step’ immuno-PET pretargeting approach, based on bispecific antibodies (bsAbs) engineered to feature dual high-affinity binding activity for a fluorescein-based ¹⁸F-PET tracer and tumor markers.

Results

A copper(I)-catalysed click reaction-based radiolabeling protocol was developed for the synthesis of fluorescein-derived molecule [¹⁸F]TPF. Binding of [¹⁸F]TPF on FITC-bearing bsAbs was confirmed. An in vitro autoradiography assay demonstrated that [¹⁸F]TPF could be used for selective imaging of EpCAM-expressing OVCAR3 cells, when pretargeted with EpCAMxFITC bsAb. The versatility of the pretargeting approach was showcased in vitro using a series of fluorescein-binding bsAbs directed at various established cancer-associated targets, including the pan-carcinoma cell surface marker EpCAM, EGFR, melanoma marker MCSP (aka CSPG4), and immune checkpoint PD-L1, offering a range of potential future applications for this pretargeting platform.

Conclusion

A versatile pretargeting platform for PET imaging, which combines bispecific antibodies and a fluorescein-based ¹⁸F-tracer, is presented. It is shown to selectively target EpCAM-expressing cells in vitro and its further evaluation with different bispecific antibodies demonstrates the versatility of the approach.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41181-022-00155-2.

EANM guideline for harmonisation on molar activity or specific activity of radiopharmaceuticals: impact on safety and imaging quality

This guideline on molar activity (A_m) and specific activity (A_s) focusses on small molecules, peptides and macromolecules radiolabelled for diagnostic and therapeutic applications. In this guideline we describe the definition of A_m and A_s, and how these measurements must be standardised and harmonised. Selected examples highlighting the importance of A_m and A_s in imaging studies of saturable binding sites will be given, and the necessity of using appropriate materials and equipment will be discussed. Furthermore, common A_m pitfalls and remedies are described. Finally, some aspects of A_m in relation the emergence of a new generation of highly sensitive PET scanners will be discussed.

Vascular uptake on 18F-sodium fluoride positron emission tomography: precursor of vascular calcification?

BACKGROUND

Microcalcifications cannot be identified with the present resolution of CT; however, 18F-sodium fluoride (18F-NaF) positron emission tomography (PET) imaging has been proposed for non-invasive identification of microcalcification. The primary objective of this study was to assess whether 18F-NaF activity can assess the presence and predict the progression of CT detectable vascular calcification.

METHODS AND RESULTS

The data of two longitudinal studies in which patients received a 18F-NaF PET-CT at baseline and after 6 months or 1-year follow-up were used. The target to background ratio (TBR) was measured on PET at baseline and CT calcification was quantified in the femoral arteries at baseline and follow-up. 128 patients were included. A higher TBR at baseline was associated with higher calcification mass at baseline and calcification progression (β = 1.006 [1.005-1.007] and β = 1.002 [1.002-1.003] in the studies with 6 months and 1-year follow-up, respectively). In areas without calcification at baseline and where calcification developed at follow-up, the TBR was .11-.13 (P < .001) higher compared to areas where no calcification developed.

CONCLUSION

The activity of 18F-NaF is related to the amount of calcification and calcification progression. In areas where calcification formation occurred, the TBR was slightly but significantly higher.

The effects of molar activity on [18F]FDOPA uptake in patients with neuroendocrine tumors

Background

6-[¹⁸F]fluoro-l-3,4-dihydroxyphenyl alanine ([¹⁸F]FDOPA) is a commonly used PET tracer for the detection and staging of neuroendocrine tumors. In neuroendocrine tumors, [¹⁸F]FDOPA is decarboxylated to [¹⁸F]dopamine via the enzyme amino acid decarboxylase (AADC), leading to increased uptake when there is increased AADC activity. Recently, in our hospital, a new GMP compliant multi-dose production of [¹⁸F]FDOPA has been developed, [¹⁸F]FDOPA-H, resulting in a higher activity yield, improved molar activity and a lower administered mass than the conventional method ([¹⁸F]FDOPA-L).

Aims

This study aimed to investigate whether the difference in molar activity affects the [¹⁸F]FDOPA uptake at physiological sites and in tumor lesions, in patients with NET. It was anticipated that the specific uptake of [¹⁸F]FDOPA-H would be equal to or higher than [¹⁸F]FDOPA-L.

Methods

We retrospectively analyzed 49 patients with pathologically confirmed NETs and stable disease who underwent PET scanning using both [¹⁸F]FDOPA-H and [¹⁸F]FDOPA-L within a time span of 5 years. A total of 98 [¹⁸F]FDOPA scans (49 [¹⁸F]FDOPA-L and 49 [¹⁸F]FDOPA-H with average molar activities of 8 and 107 GBq/mmol) were analyzed. The SUVmean was calculated for physiological organ uptake and SUVmax for tumor lesions in both groups for comparison, and separately in subjects with low tumor load (1–2 lesions) and higher tumor load (3–10 lesions).

Results

Comparable or slightly higher uptake was demonstrated in various physiological uptake sites in subjects scanned with [¹⁸F]FDOPA-H compared to [¹⁸F]FDOPA-L, with large overlap being present in the interquartile ranges. Tumor uptake was slightly higher in the [¹⁸F]FDOPA-H group with 3–10 lesion (SUVmax 6.83 vs. 5.19, p < 0.001). In the other groups, no significant differences were seen between H and L.

Conclusion

[18F]FDOPA-H provides a higher activity yield, offering the possibility to scan more patients with one single production. Minor differences were observed in SUV’s, with slight increases in uptake of [¹⁸F]FDOPA-H in comparison to [¹⁸F]FDOPA-L. This finding is not a concern for clinical practice, but could be of importance when quantifying follow-up scans while introducing new production methods with a higher molar activity of [¹⁸F]FDOPA.

First clinical assessment of [18F]MC225, a novel fluorine-18 labelled PET tracer for measuring functional P-glycoprotein at the blood-brain barrier

OBJECTIVE

5-(1-(2-[¹⁸F]fluoroethoxy))-[3-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-propyl]-5,6,7,8-tetrahydronaphthalen ([¹⁸F]MC225) is a selective substrate for P-glycoprotein (P-gp), possessing suitable properties for measuring overexpression of P-gp in the brain. This is the first-in-human study to examine safety, radiation dosimetry and P-gp function at the blood-brain barrier (BBB) of [¹⁸F]MC225 in healthy subjects.

METHODS

[¹⁸F]MC225 biodistribution and dosimetry were determined in 3 healthy male subjects, using serial 2 h and intermittent 4 and 6 h whole-body PET scans acquired after [¹⁸F]MC225 injection. Dynamic [¹⁸F]MC225 brain PET (90 min) was obtained in 5 healthy male subjects. Arterial blood was sampled at various time intervals during scanning and the fraction of unchanged [¹⁸F]MC225 in plasma was determined. T1-weighted MRI was performed for anatomical coregistration. Total distribution volume (V_T) was estimated using 1- and 2-tissue-compartment models (1-TCM and 2-TCM, respectively). V_T was also estimated using the Logan graphical method (Logan plot) (t* = 20 min). Surrogate parameters without blood sampling (area-under the curve [AUC] of regional time-activity curves [TACs] and negative slope of calculated TACs) were compared with the V_T values.

RESULTS

No serious adverse events occurred throughout the study period. Although biodistribution implied hepatobiliary excretion, secretion of radioactivity from liver to small intestine through the gallbladder was very slow. Total renal excreted radioactivity recovered during 6 h after injection was < 2%ID. Absorbed dose was the highest in the pancreas (mean ± SD, 203 ± 45 μGy/MBq) followed by the liver (83 ± 11 μGy/MBq). Mean effective dose with and without urination was 17 ± 1 μSv/MBq. [¹⁸F]MC225 readily entered the brain, distributing homogeneously in grey matter regions. 2-TCM provided lower Akaike information criterion scores than did 1-TCM. V_T estimated by Logan plot was well correlated with that of 2-TCM (r² > 0.9). AUCs of TACs were positively correlated with V_T (2-TCM) values (r²: AUC_0-60 min = 0.61, AUC_0-30 min = 0.62, AUC_30-60 min = 0.59, p < 0.0001). Negative slope of SUV TACs was negatively correlated with V_T (2-TCM) values (r² = 0.53, p < 0.0001).

CONCLUSIONS

This initial evaluation indicated that [¹⁸F]MC225 is a suitable and safe PET tracer for measuring P-gp function at the BBB.

In Vivo Induction of P-Glycoprotein Function can be Measured with [18F]MC225 and PET

P-Glycoprotein (P-gp) is an efflux pump located at the blood-brain barrier (BBB) that contributes to the protection of the central nervous system by transporting neurotoxic compounds out of the brain. A decline in P-gp function has been related to the pathogenesis of neurodegenerative diseases. P-gp inducers can increase the P-gp function and are considered as potential candidates for the treatment of such disorders. The P-gp inducer MC111 increased P-gp expression and function in SW480 human colon adenocarcinoma and colo-320 cells, respectively. Our study aims to evaluate the P-gp inducing effect of MC111 in the whole brain in vivo, using the P-gp tracer [18F]MC225 and positron emission tomography (PET). Eighteen Wistar rats were treated with either vehicle solution, 4.5 mg/kg of MC111 (low-dose group), or 6 mg/kg of MC111 (high-dose group). Animals underwent a 60 min dynamic PET scan with arterial-blood sampling, 24 h after treatment with the inducer. Data were analyzed using the 1-tissue-compartment model and metabolite-corrected plasma as the input function. Model parameters such as the influx constant (K1) and volume of distribution (VT) were calculated, which reflect the in vivo P-gp function. P-gp and pregnane xenobiotic receptor (PXR) expression levels of the whole brain were assessed using western blot. The administration of MC111 decreased K1 and VT of [18F]MC225 in the whole brain and all of the selected brain regions. In the high-dose group, whole-brain K1 was decreased by 34% (K1-high-dose = 0.20 ± 0.02 vs K1-control = 0.30 ± 0.02; p < 0.001) and in the low-dose group by 7% (K1-low-dose = 0.28 ± 0.02 vs K1-control = 0.30 ± 0.02; p = 0.42) compared to controls. Whole-brain VT was decreased by 25% in the high-dose group (VT-high-dose = 5.92 ± 0.41 vs VT-control = 7.82 ± 0.38; p < 0.001) and by 6% in the low-dose group (VT-low-dose = 7.35 ± 0.38 vs VT-control = 7.82 ± 0.37; p = 0.38) compared to controls. k2 values did not vary after treatment. The treatment did not affect the metabolism of [18F]MC225. Western blot studies using the whole-brain tissue did not detect changes in the P-gp expression, however, preliminary results using isolated brain capillaries found an increasing trend up to 37% in treated rats. The decrease in K1 and VT values after treatment with the inducer indicates an increase in the P-gp functionality at the BBB of treated rats. Moreover, preliminary results using brain endothelial cells also sustained the increase in the P-gp expression. In conclusion, the results verify that MC111 induces P-gp expression and function at the BBB in rats. An increasing trend regarding the P-gp expression levels is found using western blot and an increased P-gp function is confirmed with [18F]MC225 and PET.

A new approach to produce [18F]MC225 via one-step synthesis, a PET radiotracer for measuring P-gp function

Background

[¹⁸F]MC225 is a radiotracer for imaging P-glycoprotein (P-gp) function at the blood-brain barrier. The P-gp function can be altered due to different factors, for instance, decreased P-gp function has been described in patients with Alzheimer’s or Parkinson’s Disease. The current applied radiosynthesis of [¹⁸F]MC225 involves 2 steps, including the distillation of the [¹⁸F] fluoroethylbromide intermediate. To develop a more robust synthetic procedure, it is of interest to produce the radiotracer via a 1-step synthesis. The present study describes a new synthetic approach to produce [¹⁸F]MC225 via direct ¹⁸F-fluorination. Moreover, we also provide the appropriate conditions for the automation of the synthesis. A mesylate precursor was synthesized via a multi-step synthetic route and used for the radiolabeling. The nucleophilic substitution of the mesylate group by [¹⁸F] Fluoride was automated in two different synthesis modules: IBA Synthera and Eckert and Ziegler PharmTracer (E&Z).

Results

The mesylate precursor was synthesized in 7 steps starting with 5-hydroxy-1-tetralone (commercially available) in practical yields. The stability of the precursor was improved via mesylate salt formation method. The radiolabeling was done by adding the mesylate precursor dissolved in DMF to the dried [¹⁸F]KF/K_2.2.2 complex and heating at 140 °C for 30 min. Quality control by UPLC confirmed the production of [¹⁸F]MC225 with a molar activity (A_m) higher than 100 GBq/micromole. The synthesis time in Synthera was 106 min and the product was obtained with a radiochemical purity higher than 95% and RCY of 6.5%, while the production in E&Z lasted 120 min and the product had a lower radiochemical purity (91%) and RCY (3.8%).

Conclusions

[¹⁸F]MC225 was successfully produced via a 1-step reaction. The procedure is suitable for automation using commercially available synthesis modules. The automation of the radiosynthesis in the Synthera module allows the production of the [¹⁸F]MC225 by a reliable and simple method.

Ultrafast Photoclick Reaction for Selective 18F-Positron Emission Tomography Tracer Synthesis in Flow

The development of very fast, clean, and selective methods for indirect labeling in PET tracer synthesis is an ongoing challenge. Here we present the development of an ultrafast photoclick method for the synthesis of short-lived ¹⁸F-PET tracers based on the photocycloaddition reaction of 9,10-phenanthrenequinones with electron-rich alkenes. The respective precursors are synthetically easily accessible and can be functionalized with various target groups. Using a flow photo-microreactor, the photoclick reaction can be performed in 60 s, and clinically relevant tracers for prostate cancer and bacterial infection imaging were prepared to demonstrate practicality of the method.

Cross-coupling of [11C]methyllithium for 11C-labelled PET tracer synthesis

The cross-coupling of aryl bromides with [¹¹C]CH₃Li for the labelling of a variety of tracers for positron emission tomography (PET) is presented. The radiolabelled products were obtained in excellent yields, at rt and after short reaction times (3-5 min) compatible with the half-life of ¹¹C (20.4 min). The automation of the protocol on a synthesis module is investigated, representing an important step towards a fast method for the synthesis of ¹¹C-labelled compounds for PET imaging.

Pharmacokinetic Modeling of (R)-[11C]verapamil to Measure the P-Glycoprotein Function in Nonhuman Primates

(R)-[¹¹C]verapamil is a radiotracer widely used for the evaluation of the P-glycoprotein (P-gp) function at the blood–brain barrier (BBB). Several studies have evaluated the pharmacokinetics of (R)-[¹¹C]verapamil in rats and humans under different conditions. However, to the best of our knowledge, the pharmacokinetics of (R)-[¹¹C]verapamil have not yet been evaluated in nonhuman primates. Our study aims to establish (R)-[¹¹C]verapamil as a reference P-gp tracer for comparison of a newly developed P-gp positron emission tomography (PET) tracer in a species close to humans. Therefore, the study assesses the kinetics of (R)-[¹¹C]verapamil and evaluates the effect of scan duration and P-gp inhibition on estimated pharmacokinetic parameters. Three nonhuman primates underwent two dynamic 91 min PET scans with arterial blood sampling, one at baseline and another after inhibition of the P-gp function. The (R)-[¹¹C]verapamil data were analyzed using 1-tissue compartment model (1-TCM) and 2-tissue compartment model fits using plasma-corrected for polar radio-metabolites or non-corrected for radio-metabolites as an input function and with various scan durations (10, 20, 30, 60, and 91 min). The preferred model was chosen according to the Akaike information criterion and the standard errors (SE %) of the estimated parameters. 1-TCM was selected as the model of choice to analyze the (R)-[¹¹C]verapamil data at baseline and after inhibition and for all scan durations tested. The volume of distribution (V_T) and the efflux constant k₂ estimations were affected by the evaluated scan durations, whereas the influx constant K₁ estimations remained relatively constant. After P-gp inhibition (tariquidar, 8 mg/kg), in a 91 min scan duration, the whole-brain V_T increased significantly up to 208% (p < 0.001) and K₁ up to 159% (p < 0.001) compared with baseline scans. The k₂ values decreased significantly after P-gp inhibition in all the scan durations except for the 91 min scans. This study suggests the use of K₁, calculated with 1-TCM and using short PET scans (10 to 30 min), as a suitable parameter to measure the P-gp function at the BBB of nonhuman primates.

Induced expression of P-gp and BCRP transporters on brain endothelial cells using transferrin functionalized nanostructured lipid carriers: A first step of a potential strategy for the treatment of Alzheimer's disease

P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) are two transporters expressed in human neural stem/progenitor cells and at the Blood-Brain Barrier (BBB) level with decreased activity in the early stage of Alzheimer's disease (AD). Both proteins, have a protective role for the embryonic stem cells in the early developmental step, maintaining them in an undifferentiated state, and limit the access of exogenous and endogenous agents to the brain. Recently, MC111 selected from a P-gp/BCRP ligands library was investigated as multitarget strategy for AD treatment, considering its ability to induce the expression and activity of both proteins. However, MC111 clinical use could be limited for the ubiquitous physiological expression of efflux transporters and its moderate toxicity towards endothelial cells. Therefore, a selective MC111 delivery system based on nanostructured lipid carriers (NLC) functionalized with transferrin were developed. The results proved the formation of NLC with average size about 120 nm and high drug encapsulation efficiency (EE% greater than 50). In vitro studies on hCMEC/D3 cells revealed that the MC111 was selectively released by NLC at BBB level and then inducing the activity and expression of BCRP and P-gp, involved in the clearance of amyloid β peptide on brain endothelial cells.

IAEA contribution to the development of 64Cu radiopharmaceuticals for theranostic applications

Copper-64 is a very attractive radioisotope with unique nuclear properties that allow using it as both a diagnostic and therapeutic agent, thus providing an almost ideal example of a theranostic radionuclide. A characteristic of Cu-64 stems from the intrinsic biological nature of copper ions that play a fundamental role in a large number of cellular processes. Cu-64 is a radionuclide that reflects the natural biochemical pathways of Cu-64 ions, therefore, can be exploited for the detection and therapy of certain malignancies and metabolic diseases. Beside these applications of Cu-64 ions, this radionuclide can be also used for radiolabelling bifunctional chelators carrying a variety of pharmacophores for targeting different biological substrates. These include peptide-based substrates and immunoconjugates as well as small-molecule bioactive moieties. Fueled by the growing interest of Member States (MS) belonging to the International Atomic Energy Agency (IAEA) community, a dedicated Coordinated Research Project (CRP) was initiated in 2016, which recruited thirteen participating MS from four continents. Research activities and collaborations between the participating countries allowed for collection of an impressive series of results, particularly on the production, preclinical evaluation and, in a few cases, clinical evaluation of various ⁶⁴Cu-radiopharmaceuticals that may have potential impact on future development of the field. Since this CRP was finalized at the beginning of 2020, this short review summarizes outcomes, outputs and results of this project with the purpose to propagate to other MS and to the whole scientific community, some of the most recent achievements on this novel class of theranostic ⁶⁴Cu-pharmaceuticals.

Modular Medical Imaging Agents Based on Azide-Alkyne Huisgen Cycloadditions: Synthesis and Pre-Clinical Evaluation of 18 F-Labeled PSMA-Tracers for Prostate Cancer Imaging

Since the seminal contribution of Rolf Huisgen to develop the [3+2] cycloaddition of 1,3-dipolar compounds, its azide-alkyne variant has established itself as the key step in numerous organic syntheses and bioorthogonal processes in materials science and chemical biology. In the present study, the copper(I)-catalyzed azide-alkyne cycloaddition was applied for the development of a modular molecular platform for medical imaging of the prostate-specific membrane antigen (PSMA), using positron emission tomography. This process is shown from molecular design, through synthesis automation and in vitro studies, all the way to pre-clinical in vivo evaluation of fluorine-18- labeled PSMA-targeting 'F-PSMA-MIC' radiotracers (t1/2 =109.7 min). Pre-clinical data indicate that the modular PSMA-scaffold has similar binding affinity and imaging properties to the clinically used [68 Ga]PSMA-11. Furthermore, we demonstrated that targeting the arene-binding in PSMA, facilitated through the [3+2]cycloaddition, can improve binding affinity, which was rationalized by molecular modeling. The here presented PSMA-binding scaffold potentially facilitates easy coupling to other medical imaging moieties, enabling future developments of new modular imaging agents.

Pharmacokinetic Modeling of [18F]MC225 for Quantification of the P-Glycoprotein Function at the Blood-Brain Barrier in Non-Human Primates with PET

[¹⁸F]MC225 has been developed as a weak substrate of P-glycoprotein (P-gp) aimed to measure changes in the P-gp function at the blood–brain barrier with positron emission tomography. This study evaluates [¹⁸F]MC225 kinetics in non-human primates and investigates the effect of both scan duration and P-gp inhibition. Three rhesus monkeys underwent two 91-min dynamic scans with blood sampling at baseline and after P-gp inhibition (8 mg/kg tariquidar). Data were analyzed using the 1-tissue compartment model (1-TCM) and 2-tissue compartment model (2-TCM) fits using metabolite-corrected plasma as the input function and for various scan durations (10, 20, 30, 60, and 91 min). The preferred model was chosen according to the Akaike information criterion and the standard errors (%) of the estimated parameters. For the 91-min scan duration, the influx constant K₁ increased by 40.7% and the volume of distribution (V_T) by 30.4% after P-gp inhibition, while the efflux constant k₂ did not change significantly. Similar changes were found for all evaluated scan durations. K₁ did not depend on scan duration (10 min—K₁ = 0.2191 vs 91 min—K₁ = 0.2258), while V_T and k₂ did. A scan duration of 10 min seems sufficient to properly evaluate the P-gp function using K₁ obtained with 1-TCM. For the 91-min scan, V_T and K₁ can be estimated with a 2-TCM, and both parameters can be used to assess P-gp function.

Automated synthesis, preclinical toxicity, and radiation dosimetry of [18F]MC225 for clinical use: a tracer for measuring P-glycoprotein function at the blood-brain barrier

INTRODUCTION

[18F]MC225 is a selective substrate for P-glycoprotein (P-gp) that has good metabolic stability and shows higher baseline uptake compared with other P-gp substrates such as (R)-[11C]Verapamil. Prior to clinical translation, it is necessary to perform process validation of the radiosynthesis, assessment of preclinical toxicity, and radiation dosimetry.

METHODS

The production of [18F]MC225 was automated on a CFN-MPS200 multipurpose synthesizer. The acute toxicity of MC225 was evaluated at a dose of 2.5 mg/kg bodyweight, which is more than 10,000-fold the postulated maximum clinical dose of [18F]MC225. The acute toxicity of [18F]MC225 injection at a 200-fold dose, to administer a postulated dose of 185 MBq of [18F]MC225, was also evaluated after the decay-out of 18F. The mutagenicity of MC225 was studied by a reverse mutation test using Salmonella typhimurium and Escherichia coli (Ames test). In vivo biodistribution and dosimetry studies of [18F]MC225 were carried out in normal mice. Human dosimetry was estimated using OLINDA software.

RESULTS

The mean decay-corrected yields of [18F]MC225 at end of synthesis were 13%, with > 99% radiochemical purity, > 1000 GBq/μmol molar activity, and ≤ 1.5 μg/185 MBq of total chemical contents. All process validation batches complied with the product specifications and the process was confirmed to be appropriate for the production of [18F]MC225. No acute toxicity of MC225 or [18F]MC225 injection was found. No mutagenic activity was observed for MC225. The biodistribution study demonstrated both hepatobiliary and renal excretion of radioactivity. The most critical organ was the pancreas, with (63.8 μGy/MBq) or without urination (63.9 μGy/MBq) at 360 min after injection. The estimated effective dose (μSv/MBq) with and without urination at 360 min after injection was calculated as 15.7 and 16.9, respectively.

CONCLUSION

[18F]MC225 shows acceptable pharmacological safety at the dose required for adequate PET imaging. The potential risk associated with [18F]MC225 PET imaging is well within acceptable dose limits.

Test-Retest Repeatability of [18F]MC225-PET in Rodents: A Tracer for Imaging of P-gp Function

In longitudinal PET studies, animals are repeatedly anesthetized which may affect the repeatability of PET measurements. The aim of this study was to assess the effect of anesthesia on the P-gp function as well as the reproducibility of [¹⁸F]MC225 PET scans. Thus, dynamic PET scans with blood sampling were conducted in 13 Wistar rats. Seven animals were exposed to isoflurane anesthesia 1 week before the PET scan (“Anesthesia-exposed” PET). A second group of six animals was used to evaluate the reproducibility of measurements of P-gp function at the blood–brain barrier (BBB) with [¹⁸F]MC225. In this group, two PET scans were made with a 1 week interval (“Test” and “Retest” PET). Pharmacokinetic parameters were calculated using compartmental models and metabolite-corrected plasma as an input function. “Anesthesia-exposed” animals showed a 28% decrease in whole-brain volume of distribution (V_T) (p < 0.001) compared to “Test”, where the animals were not previously anesthetized. The V_T at “Retest” also decreased (19%) compared to “Test” (p < 0.001). The k₂ values in whole-brain were significantly increased by 18% in “Anesthesia-exposed” (p = 0.005) and by 15% in “Retest” (p = 0.008) compared to “Test”. However, no significant differences were found in the influx rate constant K₁, which is considered as the best parameter to measure the P-gp function. Moreover, Western Blot analysis did not find significant differences in the P-gp expression of animals not pre-exposed to anesthesia (“Test”) or pre-exposed animals (“Retest”). To conclude, anesthesia may affect the brain distribution of [¹⁸F]MC225 but it does not affect the P-gp expression or function.

Changes in cerebral oxygenation and cerebral blood flow during hemodialysis - A simultaneous near-infrared spectroscopy and positron emission tomography study

Near-infrared spectroscopy (NIRS) is used to monitor cerebral tissue oxygenation (rSO₂) depending on cerebral blood flow (CBF), cerebral blood volume and blood oxygen content. We explored whether NIRS might be a more easy applicable proxy to [¹⁵O]H₂O positron emission tomography (PET) for detecting CBF changes during hemodialysis. Furthermore, we compared potential determinants of rSO₂ and CBF. In 12 patients aged ≥ 65 years, NIRS and PET were performed simultaneously: before (T1), early after start (T2), and at the end of hemodialysis (T3). Between T1 and T3, the relative change in frontal rSO₂ (ΔrSO₂) was -8 ± 9% (P = 0.001) and -5 ± 11% (P = 0.08), whereas the relative change in frontal gray matter CBF (ΔCBF) was -11 ± 18% (P = 0.009) and -12 ± 16% (P = 0.007) for the left and right hemisphere, respectively. ΔrSO₂ and ΔCBF were weakly correlated for the left (ρ 0.31, P = 0.4), and moderately correlated for the right (ρ 0.69, P = 0.03) hemisphere. The Bland-Altman plot suggested underestimation of ΔCBF by NIRS. Divergent associations of pH, pCO₂ and arterial oxygen content with rSO₂ were found compared to corresponding associations with CBF. In conclusion, NIRS could be a proxy to PET to detect intradialytic CBF changes, although NIRS and PET capture different physiological parameters of the brain.

The effect of menaquinone-7 supplementation on vascular calcification in patients with diabetes: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Vitamin K occurs in the diet as phylloquinone and menaquinones. Observational studies have shown that both phylloquinone and menaquinone intake might reduce cardiovascular disease (CVD) risk. However, the effect of vitamin K on vascular calcification is unknown.

OBJECTIVES

The aim of this study was to assess if menaquinone supplementation, compared to placebo, decreases vascular calcification in people with type 2 diabetes and known CVD.

METHODS

In this double-blind, randomized, placebo-controlled trial, we randomly assigned men and women with type 2 diabetes and CVD to 360 µg/d menaquinone-7 (MK-7) or placebo for 6 mo. Femoral arterial calcification at baseline and 6 mo was measured with 18sodium fluoride positron emission tomography (18F-NaF PET) scans as target-to-background ratios (TBRs), a promising technique to detect active calcification. Calcification mass on conventional computed tomography (CT) scan was measured as secondary outcome. Dephosphorylated-uncarboxylated matrix Gla protein (dp-ucMGP) concentrations were measured to assess compliance. Linear regression analyses were performed with either TBR or CT calcification at follow-up as the dependent variable, and treatment and baseline TBR or CT calcification as independent variables.

RESULTS

We randomly assigned 35 patients to the MK-7 group (33 completed follow-up) and 33 to the placebo group (27 completed follow-up). After the 6-mo intervention, TBR tended to increase in the MK-7 group compared with placebo (0.25; 95% CI: -0.02, 0.51; P = 0.06), although this was not significant. Log-transformed CT calcification mass did not increase in the intervention group compared with placebo (0.50; 95% CI: -0.23, 1.36; P = 0.18). MK-7 supplementation significantly reduced dp-ucMGP compared with placebo (-205.6 pmol/L; 95% CI: -255.8, -155.3 pmol/L). No adverse events were reported.

CONCLUSION

MK-7 supplementation tended to increase active calcification measured with 18F-NaF PET activity compared with placebo, but no effect was found on conventional CT. Additional research investigating the interpretation of 18F-NaF PET activity is necessary. This trial was registered at clinicaltrials.gov as NCT02839044.

Optimization of parathyroid 11C-choline PET protocol for localization of parathyroid adenomas in patients with primary hyperparathyroidism

PURPOSE

To evaluate the optimal tracer uptake time, the minimal amount of radioactivity and the inter-observer agreement for ¹¹C-choline positron emission tomography/computed tomography (PET/CT) in patients with primary hyperparathyroidism (pHPT).

METHODS

Twenty-one patients with biochemically proven pHPT were retrospectively studied after injection of 6.3 ± 1.2 MBq/kg ¹¹C-choline. PET data of the first nine patients, scanned for up to 60 min, were reconstructed in 10-min frames from 10- to 60-min postinjection (p.i.), mimicking varying ¹¹C-choline uptake times. Parathyroid adenoma to background contrast ratios were calculated and compared, using standardized uptake values (SUVs). Data was reconstructed with varying scan durations (1, 2.5, 5, and 10 min) at 20-30-min p.i. (established optimal uptake time), mimicking less administered radioactivity. To establish the minimal required radioactivity, the SUVs in the shorter scan durations (1, 2.5, and 5 min) were compared to the 10-min scan duration to determine whether increased variability and/or statistical differences were observed. Four observers analyzed the ¹¹C-choline PET/CT in four randomized rounds for all patients.

RESULTS

SUVpeak of the adenoma decreased from 30 to 40 p.i. onwards. All adenoma/background contrast ratios did not differ from 20- to 30-min p.i. onwards. The SUVs of adenoma in the scan duration of 1, 2.5, and 5 min all differed significantly from the same SUV in the 10-min scan duration (all p = 0.012). However, the difference in absolute SUV adenoma values was well below 10% and therefore not considered clinically significant. The inter-observer analysis showed that the Fleiss' kappa of the 1-min scan were classified as "moderate," while these values were classified as "good" in the 2.5-, 5-, and 10-min scan duration. Observers scored lower certainty scores in the 1- and 2.5-min scans compared to the 5- and 10-min scan durations.

CONCLUSION

The optimal time to start PET/CT scanning in patients with pHPT is 20 min after mean injection of 6.3 MBq/kg ¹¹C-choline, with a recommended scan duration of at least 5 min. Alternatively, the radioactivity dose can be lowered by 50% while keeping a 10-min scan duration without losing the accuracy of ¹¹C-choline PET/CT interpretation.

Etidronate for Prevention of Ectopic Mineralization in Patients With Pseudoxanthoma Elasticum

BACKGROUND

In pseudoxanthoma elasticum (PXE), low pyrophosphate levels may cause ectopic mineralization, leading to skin changes, visual impairment, and peripheral arterial disease.

OBJECTIVES

The authors hypothesized that etidronate, a pyrophosphate analog, might reduce ectopic mineralization in PXE.

METHODS

In the Treatment of Ectopic Mineralization in Pseudoxanthoma Elasticum trial, adults with PXE and leg arterial calcifications (n = 74) were randomly assigned to etidronate or placebo (cyclical 20 mg/kg for 2 weeks every 12 weeks). The primary outcome was ectopic mineralization, quantified with ¹⁸fluoride positron emission tomography scans as femoral arterial wall target-to-background ratios (TBR_femoral). Secondary outcomes were computed tomography arterial calcification and ophthalmological changes. Safety outcomes were bone density, serum calcium, and phosphate.

RESULTS

During 12 months of follow-up, the TBR_femoral increased 6% (interquartile range [IQR]: -12% to 25%) in the etidronate group and 7% (IQR: -9% to 32%) in the placebo group (p = 0.465). Arterial calcification decreased 4% (IQR: -11% to 7%) in the etidronate group and increased 8% (IQR: -1% to 20%) in the placebo group (p = 0.001). Etidronate treatment was associated with significantly fewer subretinal neovascularization events (1 vs. 9, p = 0.007). Bone density decreased 4% ± 12% in the etidronate group and 6% ± 9% in the placebo group (p = 0.374). Hypocalcemia (<2.20 mmol/l) occurred in 3 versus 1 patient (8.1% vs. 2.7%, p = 0.304). Eighteen patients (48.6%) treated with etidronate, compared with 0 patients treated with placebo (p < 0.001), experienced hyperphosphatemia (>1.5 mmol/l) and recovered spontaneously.

CONCLUSIONS

In patients with PXE, etidronate reduced arterial calcification and subretinal neovascularization events but did not lower femoral ¹⁸fluoride sodium positron emission tomography activity compared with placebo, without important safety issues. (Treatment of Ectopic Mineralization in Pseudoxanthoma elasticum; NTR5180).

Synthesis of Substituted Benzaldehydes via a Two-Step, One-Pot Reduction/Cross-Coupling Procedure

The synthesis of functionalized (benz)aldehydes, via a two-step, one-pot procedure, is presented. The method employs a stable aluminum hemiaminal as a tetrahedral intermediate, protecting a latent aldehyde, making it suitable for subsequent cross-coupling with (strong nucleophilic) organometallic reagents, leading to a variety of alkyl and aryl substituted benzaldehydes. This very fast methodology also facilitates the effective synthesis of a ¹¹C radiolabeled aldehyde. Aluminum–ate complexes enable transmetalation of alkyl fragments onto palladium and subsequent cross-coupling.

99mTc-HYNIC-IL-2 scintigraphy to detect acute rejection in lung transplantation patients: a proof-of-concept study

Rationale

Acute allograft rejection is one of the major complications after lung transplantation, and adequate and early recognition is important. Till now, the reference standard to detect acute rejection is the histopathological grading of transbronchial biopsies (TBBs). Acute rejection is characterised by high levels of activated T lymphocytes. Interleukin-2 (IL-2) binds specifically to high-affinity IL-2 receptors expressed on the cell membrane of activated T lymphocytes. The aim of this proof-of-concept study was to evaluate if non-invasive imaging with ^99mTc-HYNIC-IL-2 is able to detect acute rejection after lung transplantation.

Methods

^99mTc-HYNIC-IL-2 scintigraphy (static, SPECT/CT of the lungs) was performed shortly before routine transbronchial biopsy (pathology as reference standard). Scans were scored as likely or unlikely for rejection, and semiquantitative analysis (target-to-background ratio) was performed.

Results

Thirteen patients were included of which 3 showed acute rejection at transbronchial biopsy; in 2 of these patients (scored as graded 2–3 at pathology), the scan was scored likely for rejection, and in 1 patient (scored grade 1 at pathology), the scan was scored unlikely. No correlation was found between biopsy results and semiquantitative analysis.

Conclusion

^99mTc-HYNIC-IL-2 scintigraphy proved to be a good technique to detect grade 2 and 3 acute rejection in a small sample population of patients after lung transplantation. Larger studies are necessary to really show the added value of this non-invasive specific imaging technique over transbronchial biopsy. Alternatively, imaging with the PET tracer ¹⁸F-IL-2 may be useful for this purpose.

Hemodialysis Induces an Acute Decline in Cerebral Blood Flow in Elderly Patients

The initiation of hemodialysis is associated with an accelerated decline of cognitive function and an increased incidence of cerebrovascular accidents and white matter lesions. Investigators have hypothesized that the repetitive circulatory stress of hemodialysis induces ischemic cerebral injury, but the mechanism is unclear. We studied the acute effect of conventional hemodialysis on cerebral blood flow (CBF), measured by [¹⁵O]H₂O positron emission tomography-computed tomography (PET-CT). During a single hemodialysis session, three [¹⁵O]H₂O PET-CT scans were performed: before, early after the start of, and at the end of hemodialysis. We used linear mixed models to study global and regional CBF change during hemodialysis. Twelve patients aged ≥65 years (five women, seven men), with a median dialysis vintage of 46 months, completed the study. Mean (±SD) arterial BP declined from 101±11 mm Hg before hemodialysis to 93±17 mm Hg at the end of hemodialysis. From before the start to the end of hemodialysis, global CBF declined significantly by 10%±15%, from a mean of 34.5 to 30.5 ml/100g per minute (difference, -4.1 ml/100 g per minute; 95% confidence interval, -7.3 to -0.9 ml/100 g per minute; P=0.03). CBF decline (20%) was symptomatic in one patient. Regional CBF declined in all volumes of interest, including the frontal, parietal, temporal, and occipital lobes; cerebellum; and thalamus. Higher tympanic temperature, ultrafiltration volume, ultrafiltration rate, and pH significantly associated with lower CBF. Thus, conventional hemodialysis induces a significant reduction in global and regional CBF in elderly patients. Repetitive intradialytic decreases in CBF may be one mechanism by which hemodialysis induces cerebral ischemic injury.

An innovative small molecule for promoting neuroreparative strategies

In this study, a new regenerative strategy to treat several neurodegenerative diseases is suggested by the use of a multitarget approach induced by our small molecule, MC111. Considering the importance of P-gp and BCRP expression on stem cell differentiation and the involvement of TLR4 on neurodegeneration processes, we investigated the effect of MC111, belonging to our library of P-gp active compounds on: (i) TLR4 signaling; (ii) P-gp and BCRP activity and expression; (iii) neurite sprouting. The observed findings exerted by MC111, open a new scenario for a multitarget and regenerative approach in neurodegenerative diseases encouraging the in vivo evaluation of MC111 as new tool in neuroreparative medicine.

In this study, a new regenerative strategy to treat several neurodegenerative diseases is suggested by the use of a multitarget approach induced by our small molecule, MC111.

PET Tracers for Imaging of ABC Transporters at the Blood-Brain Barrier: Principles and Strategies

ABC transporters at the human blood-brain barrier protect the brain against the entry of harmful compounds but may also limit (or prevent) the cerebral entry of therapeutic drugs (e.g. anti-epileptics, antidepressants and antipsychotics). The efflux function of these transporters may be impaired in neurodegenerative disorders like Alzheimer and Parkinson disease. For such reasons, there is much interest in modulation of the efflux function of ABC transporters and in the monitoring of this function with positron emission tomography (PET). The efflux function of P-glycoprotein, an important member of the ABC transporter family, can be quantified with the PET tracer (R)-[11C]verapamil, but the lipophilicity of this probe and the formation of radioactive metabolites which enter the brain complicate such measurements considerably. (R)-[11C]verapamil is also not very suitable for the detection of P-gp upregulation, as may occur in epilepsy or drug resistance. Current radiochemical efforts are therefore focused on the development of PET probes with improved characteristics, for example; capability to detect both up- and down regulation of transporter function and expression, a better metabolic profile (no brain-entering metabolites), reduced lipophilicity and a longer physical half-life (labeling with 18F instead of 11C).

Synthesis and Evaluation of New Fluorine-18 Labeled Verapamil Analogs To Investigate the Function of P-Glycoprotein in the Blood-Brain Barrier

P-glycoprotein is an efflux transporter located in the blood-brain barrier. (R)-[11C]Verapamil is widely used as a PET tracer to investigate its function in patients with epilepsy, Alzheimer's disease, and other neurodegenerative diseases. Currently it is not possible to use this successful tracer in clinics without a cyclotron, because of the short half-life of carbon-11. We developed two new fluorine-18 labeled (R)-verapamil analogs, with the benefit of a longer half-life. The synthesis of (R)-N-[18F]fluoroethylverapamil ([18F]1) and (R)-O-[18F]fluoroethylnorverapamil ([18F]2) has been described. [18F]1 was obtained in reaction of (R)-norverapamil with the volatile [18F]fluoroethyltriflate acquired from bromoethyltosylate and a silver trilate column with a radiochemical yield of 2.7% ± 1.2%. [18F]2 was radiolabeled by direct fluorination of precursor 13 and required final Boc-deprotection with TFA resulting in a radiochemical yield of 17.2% ± 9.9%. Both tracers, [18F]1 and [18F]2, were administered to Wistar rats, and blood plasma and brain samples were analyzed for metabolic stability. Using [18F]1 and [18F]2, PET scans were performed in Wistar rats at baseline and after blocking with tariquidar, showing a 3.6- and 2.4-fold increase in brain uptake in the blocked rats, respectively. In addition, for both [18F]1 and [18F]2, PET scans in Mdr1a/b(-/-), Bcrp1(-/-), and WT mice were acquired, in which [18F]2 showed a more specific brain uptake in Mdr1a/b(-/-) mice and no increased signal in Bcrp1(-/-) mice. [18F]2 was selected as the best performing tracer and should be evaluated further in clinical studies.

Comparison of In Vitro Assays in Selecting Radiotracers for In Vivo P-Glycoprotein PET Imaging

Positron emission tomography (PET) imaging of P-glycoprotein (P-gp) in the blood-brain barrier can be important in neurological diseases where P-gp is affected, such as Alzheimer´s disease. Radiotracers used in the imaging studies are present at very small, nanomolar, concentration, whereas in vitro assays where these tracers are characterized, are usually performed at micromolar concentration, causing often discrepant in vivo and in vitro data. We had in vivo rodent PET data of [¹¹C]verapamil, (R)-N-[¹⁸F]fluoroethylverapamil, (R)-O-[¹⁸F]fluoroethyl-norverapamil, [¹⁸F]MC225 and [¹⁸F]MC224 and we included also two new molecules [¹⁸F]MC198 and [¹⁸F]KE64 in this study. To improve the predictive value of in vitro assays, we labeled all the tracers with tritium and performed bidirectional substrate transport assay in MDCKII-MDR1 cells at three different concentrations (0.01, 1 and 50 µM) and also inhibition assay with P-gp inhibitors. As a comparison, we used non-radioactive molecules in transport assay in Caco-2 cells at a concentration of 10 µM and in calcein-AM inhibition assay in MDCKII-MDR1 cells. All the P-gp substrates were transported dose-dependently. At the highest concentration (50 µM), P-gp was saturated in a similar way as after treatment with P-gp inhibitors. Best in vivo correlation was obtained with the bidirectional transport assay at a concentration of 0.01 µM. One micromolar concentration in a transport assay or calcein-AM assay alone is not sufficient for correct in vivo prediction of substrate P-gp PET ligands.

In vitro imaging of bacteria using 18F-fluorodeoxyglucose micro positron emission tomography

Positron emission tomography (PET) with fluorine-18-fluorodeoxyglucose (¹⁸F-FDG) can be applied to detect infection and inflammation. However, it was so far not known to what extent bacterial pathogens may contribute to the PET signal. Therefore, we investigated whether clinical isolates of frequently encountered bacterial pathogens take up ¹⁸F-FDG in vitro, and whether FDG inhibits bacterial growth as previously shown for 2-deoxy-glucose. 22 isolates of Gram-positive and Gram-negative bacterial pathogens implicated in fever and inflammation were incubated with ¹⁸F-FDG and uptake of ¹⁸F-FDG was assessed by gamma-counting and µPET imaging. Possible growth inhibition by FDG was assayed with Staphylococcus aureus and the Gram-positive model bacterium Bacillus subtilis. The results show that all tested isolates accumulated ¹⁸F-FDG actively. Further, ¹⁸F-FDG uptake was hampered in B. subtilis pts mutants impaired in glucose uptake. FDG inhibited growth of S. aureus and B. subtilis only to minor extents, and this effect was abrogated by pts mutations in B. subtilis. These observations imply that bacteria may contribute to the signals observed in FDG-PET infection imaging in vivo. Active bacterial FDG uptake is corroborated by the fact that the B. subtilis phosphotransferase system is needed for ¹⁸F-FDG uptake, while pts mutations protect against growth inhibition by FDG.

Evaluation of [18F]MC225 as a PET radiotracer for measuring P-glycoprotein function at the blood-brain barrier in rats: Kinetics, metabolism, and selectivity

P-glycoprotein is a protective efflux transporter at the blood-brain barrier showing altered function in many neurological disorders. The purpose of this study was to validate [¹⁸F]MC225 as a radiotracer for measuring P-glycoprotein function with positron emission tomography. Three groups of Sprague-Dawley rats were used to assess tracer uptake at baseline (group 1), after inhibition of P-glycoprotein (group 2), and after inhibition of both P-glycoprotein and breast cancer resistance protein (Bcrp, group 3). A two-tissue compartment model with a metabolite-corrected plasma input function provided the best fit to the positron emission tomography data, but parameter estimates were more reliable in a one-tissue compartment model, which was selected as the preferred model. Regional distribution volumes ( V_T) in the control group ranged from 6 to 11, which is higher than for other radiotracers. [¹⁸F]MC225 showed transporter selectivity, since inhibition of P-glycoprotein caused a two to fourfold increase in the cerebral V_T values, but additional inhibition of Bcrp did not cause any further increase. Metabolic stability of [¹⁸F]MC225 was moderate (at 1 h post-injection 15% of plasma radioactivity and 76% of brain radioactivity represented intact parent). Thus, [¹⁸F]MC225 may be a useful radiotracer to measure especially increases of P-glycoprotein function at the blood-brain barrier.

Potential Therapeutic Applications of Adenosine A2A Receptor Ligands and Opportunities for A2A Receptor Imaging

Adenosine A_2A receptors (A_2A Rs) are highly expressed in the human striatum, and at lower densities in the cerebral cortex, the hippocampus, and cells of the immune system. Antagonists of these receptors are potentially useful for the treatment of motor fluctuations, epilepsy, postischemic brain damage, or cognitive impairment, and for the control of an immune checkpoint during immunotherapy of cancer. A_2A R agonists may suppress transplant rejection and graft-versus-host disease; be used to treat inflammatory disorders such as asthma, inflammatory bowel disease, and rheumatoid arthritis; be locally applied to promote wound healing and be employed in a strategy for transient opening of the blood-brain barrier (BBB) so that therapeutic drugs and monoclonal antibodies can enter the brain. Increasing A_2A R signaling in adipose tissue is also a potential strategy to combat obesity. Several radioligands for positron emission tomography (PET) imaging of A_2A Rs have been developed in recent years. This review article presents a critical overview of the potential therapeutic applications of A_2A R ligands, the use of A_2A R imaging in drug development, and opportunities and limitations of PET imaging in future research.

18th European Symposium on Radiopharmacy and Radiopharmaceuticals

OP03 Selective extraction of medically-related radionuclides from proton-irradiated thorium targets

V. Radchenko, J.W. Engle, C. Roy, J. Griswold, M.F. Nortier, E.R. Birnbaum, M. Brugh, S. Mirzadeh, K. D. John, M.E. Fassbender

OP04 Comparison of [68Ga]FSC(succ-RGD)3 and [68Ga]NODAGA-RGD for PET imaging of αvβ3 integrin expression

Chuangyan Zhai, Gerben M. Franssen, Milos Petrik, Peter Laverman, Clemens Decristoforo

OP05 A new NPY-Y1R targeting peptide for breast cancer PET imaging

Ait-Mohand Samia, Dumulon-Perreault Véronique, Guérin Brigitte

OP06 The influence of multivalency on CCK 2 receptor targeting

D. Summer, A. Kroess, C. Rangger, H. Haas, P. Laverman, F. Gerben, E. von Guggenberg, C.Decristoforo

OP07 SPECT Imaging of αvβ3 Expression by [99mTc(N)PNP43]- Bifunctional Chimeric RGD Peptide not Cross-Reacting with αvβ5

Cristina Bolzati, Nicola Salvarese, Fiorenzo Refosco, Laura Meléndez-Alafort, Debora Carpanese, Antonio Rosato, Michele Saviano, Annarita Del Gatto, Daniela Comegna, Laura Zaccaro

OP09 New dienophiles for the inverse-electron-demand Diels-Alder reaction and for pretargeted PET imaging

Emilie Billaud, Muneer Ahamed, Frederik Cleeren, Elnaz Shahbazali, Tim Noël, Volker Hessel, Alfons Verbruggen and Guy Bormans

OP10 New complexing agent for Al18F-labelling of heat-sensitive biomolecules: Synthesis and preclinical evaluation of Al18F-RESCA1-HAS

Cleeren F, Lecina J, Koole M, Verbruggen A and Bormans G

OP11 A novel versatile precursor efficient for F-18 radiolabelling via click-chemistry

B. Lugatoa, S. Stucchia, E.A. Turollaa, L. Giulianoa, S.Toddea, P. Ferraboschib

OP12 A general applicable method to quantify unidentified UV impurities in radiopharmaceuticals

R.P. Klok, M.P.J. Mooijer, N.H. Hendrikse, A.D. Windhorst

OP13 Development of [¹⁸F]Fluoro-C-glycosides to radiolabel peptides

Collet C., Petry N., Chrétien F., Karcher G., Pellegrini-Moïse N., Lamandé-Langle S.

OP14 A Microfluidic Approach for the 68Ga-labeling of PSMAHBED-CC and NODAGA-RGD

Sarah Pfaff, Cecile Philippe, Markus Mitterhauser, Marcus Hacker, Wolfgang Wadsak

OP16 Surprising reactivity of astatine in the nucleophilic substitution of aryliodonium salts: application to the radiolabeling of antibodies

François Guérard, Yong-Sok Lee, Sébastien Gouard, Kwamena Baidoo, Cyrille Alliot, Michel Chérel, Martin W. Brechbiel, Jean-François Gestin

OP17 ⁶⁴Cu-NOTA-pertuzumab F(ab')₂ fragments, a second-generation probe for PET imaging of the response of HER2-positive breast cancer to trastuzumab (Herceptin)

Lam K, Chan C, Reilly RM

OP18 Development of radiohalogenated analogues of a avb6-specific peptide for high LET particle emitter targeted radionuclide therapy of cancer

Salomé Paillas, John Marshall, Jean-Pierre Pouget, Jane Sosabowski

OP19 Ligand Specific Efficiency (LSE) as a guide in tracer optimization

Emmanuelle Briard, Yves P. Auberson, John Reilly, Mark Healy, David Sykes

OP23 The radiosynthesis of an 18F-labeled triglyceride, developed to visualize and quantify brown adipose tissue activity

Andreas Paulus, Wouter van Marken Lichtenbelt,Felix Mottaghy, Matthias Bauwens

OP24 Influence of the fluorescent dye on the tumor targeting properties of dual-labeled HBED-CC based PSMA inhibitors

Baranski, Ann-Christin, Schäfer, Martin, Bauder-Wüst, Ulrike, Haberkorn, Uwe, Eder, Matthias, Kopka, Klaus

OP25 [18F]MEL050 as a melanin PET tracer : fully automated radiosynthesis and evaluation for the detection of pigmented melanoma in mice pulmonary metastases

Chaussard M, Hosten B, Vignal N, Tsoupko-Sitnikov V, Hernio N, Hontonnou F, Merlet P, Poyet JL, Sarda-Mantel L, Rizzo-Padoin N

OP26 Design and Preclinical Evaluation of Novel Radiofluorinated PSMA Targeting Ligands Based on PSMA-617

J. Cardinale, M. Schäfer, M. Benešová, U. Bauder-Wüst, O. Seibert, F. Giesel, U. Haberkorn, M. Eder, K. Kopka

OP27 A novel radiolabeled peptide for PET imaging of prostate cancer: 64Cu-DOTHA2-PEG-RM26

Mansour Nematallah, Paquette Michel, Ait-Mohand Samia, Dumulon-Perreault Véronique, Lecomte Roger, Guérin Brigitte

OP29 Biodistribution of [¹⁸F]Amylovis®, a new radiotracer PET imaging of β-amyloid plaques

Fernandez-Maza L, Rivera-Marrero S, Prats Capote A, Parrado-Gallego A, Fernandez-Gomez I, Balcerzyk M, Sablon-Carrazana M, Perera-Pintado A, Merceron-Martinez D, Acosta-Medina E, Rodriguez-Tanty C

OP30 Synthesis and preclinical evaluation of [11C]-BA1 PET tracer for the imaging of CSF-1R

Bala Attili, Muneer Ahamed, Guy Bormans

OP31 In vivo imaging of the MCHR1 in the ventricular system via [18F]FE@SNAP

C. Philippe, M. Zeilinger, T. Scherer, C. Fürnsinn, M. Dumanic, W. Wadsak, M. Hacker, M. Mitterhauser

OP32 Synthesis of the first carbon-11 labelled P2Y12 receptor antagonist for imaging the anti-inflammatory phenotype of activated microglia

B. Janssen, D.J. Vugts, G.T. Molenaar, U. Funke, P.S. Kruijer, F. Dollé, G. Bormans, A.A. Lammertsma, A.D. Windhorst

OP33 Radiosynthesis of a selective HDAC6 inhibitor [11C]KB631 and in vitro and ex vivo evaluation

Koen Vermeulen, Muneer Ahamed, Michael Schnekenburger, Mathy Froeyen, Dag Erlend Olberg, Marc Diederich, Guy Bormansa

OP34 Improving metabolic stability of fluorine-18 labelled verapamil analogues

Raaphorst RM, Luurtsema G, Lammertsma AA, Elsinga PH, Windhorst AD

OP36 Development of a novel PET tracer for the activin receptor-like kinase 5

Lonneke Rotteveel, Uta Funke, Peter ten Dijke, Harm Jan Bogaard, Adriaan A. Lammertsma, Albert D. Windhorst

OP37 SPECT imaging and biodistribution studies of 111In-EGF-Au-PEG nanoparticles in vivo

Lei Song, Sarah Able, Nadia Falzone, Veerle Kersemans, Katherine Vallis

OP38 Melanoma targeting with [99mTc(N)(PNP3)]-labeled NAPamide derivatives: preliminary pharmacological studies

Davide Carta, Nicola Salvarese, Wiebke Sihver, Feng Gao, Hans Jürgen Pietzsch, Barbara Biondi, Paolo Ruzza, Fiorenzo Refosco, Cristina Bolzati

OP39 [⁶⁸Ga]NODAGA-RGD: cGMP synthesis and data from a phase I clinical study

Roland Haubner, Armin Finkensted, Armin Stegmair, Christine Rangger, Clemens Decristoforo, Heinz Zoller, Irene J. Virgolin

OP44 Implementation of a GMP-grade radiopharmacy facility in Maastricht

Ivo Pooters, Maartje Lotz, Roel Wierts, Felix Mottaghy, Matthias Bauwens

OP45 Setting up a GMP production of a new radiopharmaceutical

Forsback, Sarita, Bergman Jörgen, Kivelä Riikka

OP48 In vitro and in vivo evaluation of 68-gallium labeled Fe3O4-DPD nanoparticles as potential PET/MRI imaging agents

M. Karageorgou, M. Radović, C. Tsoukalas, B. Antic, M. Gazouli, M. Paravatou-Petsotas, S. Xanthopouls, M. Calamiotou, D. Stamopoulos, S. Vranješ-Durić, P. Bouziotis

OP49 Fast PET imaging of inflammation using 68Ga-citrate with Fe-containing salts of hydroxy acids

A. S. Lunev, A. A. Larenkov, K.A. Petrosova, O. E. Klementyeva, G. E. Kodina

PP01 Installation and validation of 11C-methionine synthesis

Kvernenes, O.H., Adamsen, T.C.H.

PP02 Fully automated synthesis of 68Ga-labelled peptides using the IBA Synthera® and Synthera® Extension modules

René Martin, Sebastian Weidlich, Anna-Maria Zerges, Cristiana Gameiro, Neva Lazarova, Marco Müllera

PP03 GMP compliant production of ¹⁵O-labeled water using IBA 18 MeV proton cyclotron

Gert Luurtsema, Michèl de Vries, Michel Ghyoot, Gina van der Woude, Rolf Zijlma, Rudi Dierckx, Hendrikus H. Boersma, Philip H. Elsinga

PP04 In vitro Nuclear Imaging Potential of New Subphthalocyanine and Zinc Phthalocyanine

Fatma Yurt Lambrecht, Ozge Er, Mine Ince, Cıgır Biray Avci, Cumhur Gunduz, Fatma Aslihan Sarı

PP05 Synthesis, Photodynamic Therapy Efficacy and Nuclear Imaging Potential of Zinc Phthalocyanines

Kasim Ocakoglu, Ozge Er, Onur Alp Ersoz, Fatma Yurt Lambrecht, Mine Ince, Cagla Kayabasi, Cumhur Gunduz

PP06 Radio-U(H)PLC – the Search on the Optimal Flow Cell for the γ-Detector

Torsten Kniess, Sebastian Meister, Steffen Fischer, Jörg Steinbach

PP07 Radiolabeling, characterization & biodistribution study of cysteine and its derivatives with Tc99m

Rabia Ashfaq, Saeed Iqbal, Atiq-ur-Rehman, Irfan ullah Khan

PP08 Radiolabelling of poly (lactic-co.glycolic acid) (PLGA) nanoparticles with 99mTC

R Iglesias-Jerez, Cayero-Otero, L. Martín-Banderas, A. Perera-Pintado, I. Borrego-Dorado

PP09 Development of [¹⁸F]PD-410 as a non-peptidic PET radiotracer for gastrin releasing peptide receptors

Ines Farinha-Antunes, Chantal Kwizera, Enza Lacivita, Ermelinda Lucente, Mauro Niso, Paola De Giorgio, Roberto Perrone, Nicola A. Colabufo, Philip H. Elsinga, Marcello Leopoldo

PP10 An improved nucleophilic synthesis of 2-(3,4-dimethoxyphenyl)-6-(2-[18F]fluoroethoxy) benzothiazole ([18F]FEDMBT), potential diagnostic agent for breast cancer imaging by PET

V.V. Vaulina, O.S. Fedorova, V.V. Orlovskaja, С.L. Chen, G.Y. Li, F.C. Meng, R.S. Liu, H.E. Wang, R.N. Krasikova

PP11 Internal radiation dose assessment of radiopharmaceuticals prepared with accelerator-produced 99mTc

Laura Meléndez-Alafort, Mohamed Abozeid, Guillermina Ferro-Flores, Anna Negri, Michele Bello, Nikolay Uzunov, Martha Paiusco, Juan Esposito, Antonio Rosato

PP12 A specialized five-compartmental model software for pharmacokinetic parameters calculation

Laura Meléndez-Alafort, Cristina Bolzati, Guillermina Ferro-Flores, Nicola Salvarese, Debora Carpanese, Mohamed Abozeid, Antonio Rosato, Nikolay Uzunov

PP13 Molecular imaging of the pharmacokinetic behavior of low molecular weight ¹⁸F-labeled PEtOx in comparison to ⁸⁹Zr-labeled PEtOx

Palmieri L, Verbrugghen T, Glassner M, Hoogenboom R, Staelens S, Wyffels L

PP14 Towards nucleophilic synthesis of the α-[18F]fluoropropyl-L-dihydroxyphenylalanine

V. V. Orlovskaja, O. F. Kuznetsova, O. S. Fedorova, V. I. Maleev, Yu. N. Belokon, A. Geolchanyan, A. S. Saghyan, L. Mu, R. Schibli, S. M. Ametamey, R. N. Krasikova

PP15 A convenient one-pot synthesis of [18F]clofarabine

Revunov, Evgeny, Malmquist, Jonas, Johnström, Peter, Van Valkenburgh, Juno, Steele, Dalton, Halldin, Christer, Schou, Magnus

PP16 BODIPY-estradiol conjugates as multi-modality tumor imaging agents

Samira Osati,Michel Paquette,Simon Beaudoin,Hasrat Ali,Brigitte Guerin, Jeffrey V. Leyton, Johan E. van Lier

PP17 Easy and high yielding synthesis of 68Ga-labelled HBED-PSMA and DOTA-PSMA by using a Modular-Lab Eazy automatic synthesizer

Di Iorio V, Iori M, Donati C, Lanzetta V, Capponi PC, Rubagotti S, Dreger T, Kunkel F, Asti M

PP18 Synthesis and evaluation of fusarinine C-based octadentate bifunctional chelators for zirconium-89 labelling

Chuangyan Zhai, Christine Rangger, Dominik Summer, Hubertus Haas, Clemens Decristoforo

PP19 Fully automated production of [18F]NaF using a re-configuring FDG synthesis module.

Suphansa Kijprayoon, Ananya Ruangma, Suthatip Ngokpol, Samart Tuamputsha

PP20 Extension of the Carbon-11 Small Labeling Agents Toolbox and Conjugate Addition

Ulrike Filp, Anna Pees, Carlotta Taddei, Aleksandra Pekošak, Antony D. Gee, Alex J. Poot, Albert D. Windhorst

PP21 In vitro studies on BBB penetration of pramipexole encapsulated theranostic liposomes for the therapy of Parkinson’s disease

Mine Silindir Gunay, A. Yekta Ozer, Suna Erdogan, Ipek Baysal, Denis Guilloteau, Sylvie Chalon

PP22 Factors affecting tumor uptake of 99mTc-HYNIC-VEGF165

Filippo Galli, Marco Artico, Samanta Taurone, Enrica Bianchi, Bruce D. Weintraub, Mariusz Skudlinski, Alberto Signore

PP23 Rhenium-188: a suitable radioisotope for targeted radiotherapy

Nicolas Lepareur, Nicolas Noiret, François Hindré, Franck Lacœuille, Eric Benoist, Etienne Garin

PP24 Preparation of a broad palette of 68Ga radiopharmaceuticals for clinical applications

Trejo-Ballado F, Zamora-Romo E, Manrique-Arias JC, Gama-Romero HM, Contreras-Castañon G, Tecuapetla-Chantes RG, Avila-Rodriguez MA

PP25 68Ga-peptide preparation with the use of two 68Ge/68Ga-generators

H. Kvaternik, D. Hausberger, C. Zink, B. Rumpf, R. M. Aigner

PP26 Assay of HEPES in 68Ga-peptides by HPLC

H. Kvaternik, D. Hausberger, B. Rumpf, R. M. Aigner

PP27 Preparation, in vitro and in vivo evaluation of a 99mTc(I)-Diethyl Ester (S,S)-Ethylenediamine- N,N´-DI-2-(3-Cyclohexyl) Propionic acid as a target-specific radiopharmaceutical

Drina Janković, Mladen Lakić, Aleksandar Savić, Slavica Ristić, Nadežda Nikolić, Aleksandar Vukadinović, Tibor J. Sabo, Sanja Vranješ-Đurić

PP28 90Y-labeled magnetite nanoparticles for possible application in cancer therapy

S. Vranješ-Đurić, M. Radović, D. Janković, N. Nikolić, G. F. Goya, P. Calatayud, V. Spasojević, B. Antić

PP29 Simplified automation of the GMP production of 68Ga-labelled peptides

David Goblet, Cristiana Gameiro, Neva Lazarova

PP30 Combining commercial production of multi-products in a GMP environment with Clinical & R&D activities

Cristiana Gameiro, Ian Oxley, Antero Abrunhosa, Vasko Kramer, Maria Vosjan, Arnold Spaans

PP31 ⁹⁹mTc(CO)3-labeling and Comparative In-Vivo Evaluation of Two Clicked cRGDfK Peptide Derivatives

Kusum Vats, Drishty Satpati, Haladhar D Sarma, Sharmila Banerjee

PP32 Application of AnaLig resin for 99mTc separation from molybdenum excess

Wojdowska W., Pawlak D.W., Parus L. J., Garnuszek P., Mikołajczak R.

PP33 Constraints for selection of suitable precursor for one-step automated synthesis of [18F]FECNT, the dopamine transporter ligand

Pijarowska-Kruszyna J, Jaron A, Kachniarz A, Malkowski B, Garnuszek P, Mikolajczak R

PP34 Gamma scintigraphy studies with 99mTc- amoxicillin sodium in bacterially infected and sterile inflamed rats

Derya Ilem-Ozdemir, Oya Caglayan-Orumlu, Makbule Asikoglu

PP35 Preparation of 99mTc- Amoxicillin Sodium Lyophilized Kit

Derya Ilem-Ozdemir, Oya Caglayan-Orumlu, Makbule Asikoglu

PP36 Outfits of Tracerlan FXC-PRO for 11C-Labeling

Arponen Eveliina, Helin Semi, Saarinen Timo, Vauhkala Simo, Kokkomäki Esa, Lehikoinen Pertti

PP37 Microfluidic synthesis of ω-[18F]fluoro-1-alkynes

Mariarosaria De Simone, Giancarlo Pascali, Ludovica Carzoli, Mauro Quaglierini, Mauro Telleschi, Piero A. Salvadori

PP38 Automated 18F-flumazenil production using chemically resistant disposable cassettes

Phoebe Lam, Martina Aistleitner, Reinhard Eichinger, Christoph Artner

PP39 The effect of the eluent solutions (TBAHCO3, Kryptand K2.2.2) on the radiochemical yields of 18F-Fluoromethylcholine

Surendra Nakka, Hemantha Kumara MC, Al-Qahtani Mohammed

PP40 [68Ga]Radiolabeling of short peptide that has a PET imaging potentials

Al-Qahtani, Mohammed, Al-Malki, Yousif

PP41 Is validation of radiochemical purity analysis in a public hospital in a developing country possible?

N Mambilima, SM Rubow

PP42 Improved automated radiosynthesis of [18F]FEPPA

N. Berroterán-Infante, M. Hacker, M. Mitterhauser, W. Wadsak

PP43 Synthesis and initial evaluation of Al18F-RESCA1-TATE for somatostatin receptor imaging with PET

Uta Funke, Frederik Cleeren, Joan Lecina, Rodrigo Gallardo, Alfons M. Verbruggen, Guy Bormans

PP44 Radiolabeling and SPECT/CT imaging of different polymer-decorated zein nanoparticles for oral administration

Rocío Ramos-Membrive, Ana Brotons, Gemma Quincoces, Laura Inchaurraga, Inés Luis de Redín, Verónica Morán, Berta García-García, Juan Manuel Irache, Iván Peñuelas

PP45 An analysis of the quality of 68Ga-DOTANOC radiolabelling over a 3 year period

Trabelsi, M., Cooper M.S.

PP46 In vivo biodistribution of adult human mesenchymal stem cells I (MSCS-ah) labeled with 99MTC-HMPAO administered via intravenous and intra-articular in animal model. Preliminary results

Alejandra Abella, Teodomiro Fuente, Antonio Jesús Montellano, Teresa Martínez, Ruben Rabadan, Luis Meseguer-Olmo

PP47 Synthesis of [¹⁸F]F-exendin-4 with high specific activity

Lehtiniemi P, Yim C, Mikkola K, Nuutila P, Solin O

PP48 Experimental radionuclide therapy with 177Lu-labelled cyclic minigastrin and human dosimetry estimations

von Guggenberg E, Rangger C, Mair C, Balogh L, Pöstényi Z, Pawlak D, Mikołajczak R

PP49 Synthesis of radiopharmaceuticals for cell radiolabelling using anion exchange column

Socan A, Kolenc Peitl P, Krošelj M, Rangger C, Decristoforo C

PP50 [68Ga]peptide production on commercial synthesiser mAIO

Collet C., Remy S., Didier R,Vergote T.,Karcher G., Véran N.

PP51 Dry kit formulation for efficient radiolabeling of 68Ga-PSMA

D. Pawlak, M. Maurin, P. Garnuszek, U. Karczmarczyk, R. Mikołajczak

PP52 Development of an experimental method using Cs-131 to evaluate radiobiological effects of internalized Auger-electron emitters

Pil Fredericia, Gregory Severin, Torsten Groesser, Ulli Köster, Mikael Jensen

PP53 Preclinical comparative evaluation of NOTA/NODAGA/DOTA CYCLO-RGD peptides labelled with Ga-68

R. Leonte, F. D. Puicea, A. Raicu, E. A. Min, R. Serban, G. Manda, D. Niculae

PP54 Synthesizer- and Kit-based preparation of prostate cancer imaging agent 68Ga-RM2

Marion Zerna, Hanno Schieferstein, Andre Müller, Mathias Berndt

PP55 Synthesis of pancreatic beta cell-specific [18F]fluoro-exendin-4 via strain-promoted aza-dibenzocyclooctyne/azide cycloaddition

Cheng-Bin Yim, Kirsi Mikkola, Pirjo Nuutila, Olof Solin

PP56 Automated systems for radiopharmacy

D. Seifert, J. Ráliš, O. Lebeda

PP57 Simple, suitable for everyday routine use quality control method to assess radionuclidic purity of cyclotron-produced 99mTc

Svetlana V. Selivanova, Helena Senta, Éric Lavallée, Lyne Caouette, Éric Turcotte, Roger Lecomte

PP58 Effective dose estimation using Monte Carlo simulation for patients undergoing radioiodine therapy

Marina Zdraveska Kochovska, Emilija Janjevik Ivanovska, Vesna Spasic Jokic

PP59 Chemical analysis of the rituximab radioimmunoconjugates in lyophilized formulations intended for oncological applications

Darinka Gjorgieva Ackova, Katarina Smilkov, Petre Makreski, Trajče Stafilov, Emilija Janevik-Ivanovska

PP61 The need and benefits of established radiopharmacy in developing African countries

Aschalew Alemu, Joel Munene Muchira, David Mwanza Wanjeh, Emilija Janevik-Ivanovska

PP62 University Master Program of Radiopharmacy – step forward for Good Radiopharmacy Education

Emilija Janevik-Ivanovska, Zoran Zdravev, Uday Bhonsle, Osso Júnior João Alberto, Adriano Duatti, Bistra Angelovska, Zdenka Stojanovska, Zorica Arsova Sarafinovska, Darko Bosnakovski, Darinka Gorgieva-Ackova, Katarina Smilkov, Elena Drakalska, Meera Venkatesh, Rubin Gulaboski

PP63 Synthesis and preclinical validations of a novel 18F-labelled RGD peptide prepared by ligation of a 2-cyanobenzothiazole with 1,2-aminothiol to image angiogenesis.

Didier J. Colin, James A. H. Inkster, Stéphane Germain, Yann Seimbille

Improved GMP-compliant multi-dose production and quality control of 6-[18F]fluoro-L-DOPA

Background

6-[¹⁸F]Fluoro-L-3,4-dihydroxyphenylalanine (FDOPA) is a frequently used radiopharmaceutical for detecting neuroendocrine and brain tumors and for the differential diagnosis of Parkinson’s disease. To meet the demand for FDOPA, a high-yield GMP-compliant production method is required. Therefore, this study aimed to improve the FDOPA production and quality control procedures to enable distribution of the radiopharmaceutical over distances.

FDOPA was prepared by electrophilic fluorination of the trimethylstannyl precursor with [¹⁸F]F₂, produced from [¹⁸O]₂ via the double-shoot approach, leading to FDOPA with higher specific activity as compared to FDOPA which was synthesized, using [¹⁸F]F₂ produced from ²⁰Ne, leading to FDOPA with a lower specific activity. The quality control of the product was performed using a validated UPLC system and compared with quality control with a conventional HPLC system. Impurities were identified using UPLC-MS.

Results

The [¹⁸O]₂ double-shoot radionuclide production method yielded significantly more [¹⁸F]F₂ with less carrier F₂ than the conventional method starting from ²⁰Ne. After adjustment of radiolabeling parameters substantially higher amounts of FDOPA with higher specific activity could be obtained. Quality control by UPLC was much faster and detected more side-products than HPLC. UPLC-MS showed that the most important side-product was FDOPA-quinone, rather than 6-hydroxydopa as suggested by the European Pharmacopoeia.

Conclusion

The production and quality control of FDOPA were significantly improved by introducing the [¹⁸O]₂ double-shoot radionuclide production method, and product analysis by UPLC, respectively. As a result, FDOPA is now routinely available for clinical practice and for distribution over distances.

Feasibility of [18F]-RGD for ex vivo imaging of atherosclerosis in detection of αvβ3 integrin expression

BACKGROUND

Inflammation and angiogenesis play an important role in atherosclerotic plaque rupture. Therefore, molecular imaging of these processes could be used for determination of rupture-prone atherosclerotic plaques. αvβ3 integrin is involved in the process of angiogenesis. Targeted imaging of αvβ3 integrin has been shown to be possible in previous studies on tumor models, using radiolabeled arginine-glycine-aspartate (RGD). Our aim was to investigate feasibility of ex vivo detection of αvβ3 integrin in carotid endarterectomy (CEA) specimens.

METHODS AND RESULTS

Nineteen CEA specimens were incubated in 5 MBq [18F]-RGD-K5 for 1 hour followed by 1 hour emission microPET scan. The results were quantified in 4 mm wide segments as percent incubation dose per gram (%Inc/g). Segmental-to-total ratio was calculated and presence of αvβ3 integrin and endothelial cells in each segment was confirmed by immunohistochemical staining for CD31 and αvβ3 integrin, respectively. [18F]-RGD-K5 uptake was heterogeneously distributed across CEA specimens and was localized within the vessel wall. Significant correlations were observed between segmental-to-total ratio with αvβ3 integrin staining score (r = 0.58, P = .038) and CD31 staining score (ρ = 0.67, P < .002).

CONCLUSION

This study showed the feasibility of integrin imaging by determination of αvβ3 integrin expression in human atherosclerotic plaques.

Synthesis and Preclinical Evaluation of Three Novel Fluorine-18 Labeled Radiopharmaceuticals for P-Glycoprotein PET Imaging at the Blood-Brain Barrier

P-Glycoprotein (P-gp), along with other transporter proteins at the blood-brain barrier (BBB), limits the entry of many pharmaceuticals into the brain. Altered P-gp function has been found in several neurological diseases. To study the P-gp function, many positron emission tomography (PET) radiopharmaceuticals have been developed. Most P-gp radiopharmaceuticals are labeled with carbon-11, while labeling with fluorine-18 would increase their applicability due to longer half-life. Here we present the synthesis and in vivo evaluation of three novel fluorine-18 labeled radiopharmaceuticals: 4-((6,7-dimethoxy-3,4-dihydroisoquinolin-2(1H)-yl)methyl)-2-(4-fluorophenyl)oxazole (1a), 2-biphenyl-4-yl-2-fluoroethoxy-6,7-dimethoxy-1,2,3,4-tetrahydro-isoquinoline (2), and 5-(1-(2-fluoroethoxy))-[3-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-propyl]-5,6,7,8-tetrahydronaphthalen (3). Compounds were characterized as P-gp substrates in vitro, and Mdr1a/b((-/-))Bcrp1((-/-)) and wild-type mice were used to assess the substrate potential in vivo. Comparison was made to (R)-[(11)C]verapamil, which is currently the most frequently used P-gp substrate. Compound [(18)F]3 was performing the best out of the new radiopharmaceuticals; it had 2-fold higher brain uptake in the Mdr1a/b((-/-))Bcrp1((-/-)) mice compared to wild-type and was metabolically quite stable. In the plasma, 69% of the parent compound was intact after 45 min and 96% in the brain. Selectivity of [(18)F]3 to P-gp was tested by comparing the uptake in Mdr1a/b((-/-)) mice to uptake in Mdr1a/b((-/-))Bcrp1((-/-)) mice, which was statistically not significantly different. Hence, [(18)F]3 was found to be selective for P-gp and is a promising new radiopharmaceutical for P-gp PET imaging at the BBB.

Cutamesine Overcomes REM Sleep Deprivation-Induced Memory Loss: Relationship to Sigma-1 Receptor Occupancy

PURPOSE

Rapid eye movement (REM) sleep deprivation (SD) decreases cerebral sigma-1 receptor expression and causes cognitive deficits. Sigma-1 agonists are cognitive enhancers. Here, we investigate the effect of cutamesine treatment in the REM SD model.

PROCEDURES

Sigma-1 receptor occupancy (RO) in the rat brain by cutamesine was determined using 1-[2-(3,4-dimethoxyphenethyl)]-4-(3-phenylpropyl)piperazine ([(11)C]SA4503) and positron emission tomography (PET), and tissue cutamesine levels were measured by ultra performance liquid chromatography (UPLC)-MS. RO was calculated from a Cunningham-Lassen plot, based on the total distribution volume of [(11)C]SA4503 determined by Logan graphical analysis. Cognitive performance was assessed using the passive avoidance (PA) test.

RESULTS

Cutamesine at a dose of 1.0 mg/kg reversed REM SD-induced cognitive deficit and occupied 92 % of the sigma-1 receptor population. A lower dose (0.3 mg/kg) occupied 88 % of the receptors but did not significantly improve cognition.

CONCLUSION

The anti-amnesic effect of cutamesine in this animal model may be related to longer exposure at a higher dose and/or drug binding to secondary targets.