Search

Introduction: The A2A adenosine receptor (A2AAR) is expressed in brain, vasculature and immune cells. According to the alterations of the A2AAR expression in multiple diseases, it is a highly attractive diagnostic and therapeutic target. We developed the A2AAR-specific PET radiotracer [18F]FLUDA and investigated it in healthy mice and piglets, in a rotenone-based mouse model of Parkinson’s disease (RMMPD) and in transgenic mice overexpressing the human A2AAR in heart (TG) [1 3]. Methods: On the basis of a one-pot two-step radiofluorination procedure, a remotely controlled automated radiosynthesis of [18F]FLUDA using the TRACERlab FX2N synthesis module was developed. In vitro autoradiography was performed with cryosections of tissue from animal models. In vivo stability was investigated in mouse by radio-HPLC analyses of blood plasma and brain homogenates. The biodistribution was investigated by dynamic PET/MR studies in healthy mice and piglets under control and blocking conditions (vehicle vs. blocking with 2.5 mg/kg tozadenant and/or 1.0 mg/kg istradefylline) and in both mouse models. The binding potential (BPND) in vivo was calculated using the simplified reference tissue modelling with the cerebellum as reference region. A single dose acute toxicity study was performed in Wistar rats according to the ICH guideline M3(R2). PET-derived radiation dosimetry was estimated in piglets. Results: A reliable and reproducible procedure for the automated production of [18F]FLUDA was successfully established (Fig. 1A) [4]. In vitro autoradiography revealed highly selective binding and high affinity of [18F]FLUDA towards the A2AAR of the three species (KD values 0.7-5.9 nM, Fig. 1B). At 15 min after i.v. injection of [18F]FLUDA in mice, the parent fraction accounted for about 100% in brain and 71% in plasma. PET studies confirmed the specific binding of [18F]FLUDA in vivo to the striatal A2AAR in mice and piglets (BPND=3.9 and 1.3, Fig. 1C). The availability of A2AAR in the P

Introduction: Glioma are clinically challenging tumors due to their location and invasiveness, limiting their complete surgical resection. Mutated isocitrate dehydrogenase enzymes (IDH) are frequent alterations - the most common being the IDH1R132H - expressed only in glioma but not in healthy brain, correlating with prognosis. Hence, the evaluation of the IDH mutation status has become essential in clinical patient stratification. Currently, the IDH mutations are determined either directly by invasive biopsies or indirectly by magnetic resonance spectroscopy. Here, we propose a transdisciplinary approach to develop an 18F-labeled ligand to detect the IDH1R132H protein directly and non-invasively by positron emission tomography (PET) imaging. Such an imaging tool could improve the selection of cancer patients who are most likely to benefit from precision medicine. In the present study, we performed the radiofluorination of AG-120 (Ivosidenib), an FDA-approved small molecule inhibitor of mutant-IDH. Methods: The stannyl precursor (HL174) was synthetized according to the published synthesis of AG-120 [1] with minor modifications. The radiosynthesis was performed by copper-mediated radiofluorination of HL174 (Fig. 1) using a TRACERlab FX2 N synthesis module. The inhibitory potency of AG-120 was measured with a diaphorase/resazurin coupled assay using recombinant IDH1R132H or IDH1 (n=2). Internalization of [18F]AG-120 were determined in vitro using U251 human glioblastoma cells stably transfected with IDH1 or IDH1R132H [2]. In vivo metabolism was investigated in healthy CD-1 mice (n=3) by radio-chromatographic analyses of plasma and brain tissue. Dynamic PET (Mediso, nanoScan® PET/CT) imaging studies were performed in nude rats bearing U251-IDH1 (n=2) or U251-IDH1R132H (n=2) glioblastoma. Results: For the first time, diastereomerically pure [18F]AG-120 was prepared by an automated copper-mediated radiolabelling approach without azeotropic drying starting from the stanny

Introduction: The A2A adenosine receptor (A2AAR) is expressed in brain, vasculature and immune cells. According to the alterations of the A2AAR expression in multiple diseases, it is a highly attractive diagnostic and therapeutic target. We developed the A2AAR-specific PET radiotracer [18F]FLUDA and investigated it in healthy mice and piglets, in a rotenone-based mouse model of Parkinson’s disease (RMMPD) and in transgenic mice overexpressing the human A2AAR in heart (TG) [1 3]. Methods: On the basis of a one-pot two-step radiofluorination procedure, a remotely controlled automated radiosynthesis of [18F]FLUDA using the TRACERlab FX2N synthesis module was developed. In vitro autoradiography was performed with cryosections of tissue from animal models. In vivo stability was investigated in mouse by radio-HPLC analyses of blood plasma and brain homogenates. The biodistribution was investigated by dynamic PET/MR studies in healthy mice and piglets under control and blocking conditions (vehicle vs. blocking with 2.5 mg/kg tozadenant and/or 1.0 mg/kg istradefylline) and in both mouse models. The binding potential (BPND) in vivo was calculated using the simplified reference tissue modelling with the cerebellum as reference region. A single dose acute toxicity study was performed in Wistar rats according to the ICH guideline M3(R2). PET-derived radiation dosimetry was estimated in piglets. Results: A reliable and reproducible procedure for the automated production of [18F]FLUDA was successfully established (Fig. 1A) [4]. In vitro autoradiography revealed highly selective binding and high affinity of [18F]FLUDA towards the A2AAR of the three species (KD values 0.7-5.9 nM, Fig. 1B). At 15 min after i.v. injection of [18F]FLUDA in mice, the parent fraction accounted for about 100% in brain and 71% in plasma. PET studies confirmed the specific binding of [18F]FLUDA in vivo to the striatal A2AAR in mice and piglets (BPND=3.9 and 1.3, Fig. 1C). The availability of A2AAR in the P

Introduction: Glioma are clinically challenging tumors due to their location and invasiveness, limiting their complete surgical resection. Mutated isocitrate dehydrogenase enzymes (IDH) are frequent alterations - the most common being the IDH1R132H - expressed only in glioma but not in healthy brain, correlating with prognosis. Hence, the evaluation of the IDH mutation status has become essential in clinical patient stratification. Currently, the IDH mutations are determined either directly by invasive biopsies or indirectly by magnetic resonance spectroscopy. Here, we propose a transdisciplinary approach to develop an 18F-labeled ligand to detect the IDH1R132H protein directly and non-invasively by positron emission tomography (PET) imaging. Such an imaging tool could improve the selection of cancer patients who are most likely to benefit from precision medicine. In the present study, we performed the radiofluorination of AG-120 (Ivosidenib), an FDA-approved small molecule inhibitor of mutant-IDH. Methods: The stannyl precursor (HL174) was synthetized according to the published synthesis of AG-120 [1] with minor modifications. The radiosynthesis was performed by copper-mediated radiofluorination of HL174 (Fig. 1) using a TRACERlab FX2 N synthesis module. The inhibitory potency of AG-120 was measured with a diaphorase/resazurin coupled assay using recombinant IDH1R132H or IDH1 (n=2). Internalization of [18F]AG-120 were determined in vitro using U251 human glioblastoma cells stably transfected with IDH1 or IDH1R132H [2]. In vivo metabolism was investigated in healthy CD-1 mice (n=3) by radio-chromatographic analyses of plasma and brain tissue. Dynamic PET (Mediso, nanoScan® PET/CT) imaging studies were performed in nude rats bearing U251-IDH1 (n=2) or U251-IDH1R132H (n=2) glioblastoma. Results: For the first time, diastereomerically pure [18F]AG-120 was prepared by an automated copper-mediated radiolabelling approach without azeotropic drying starting from the stanny

[18F]FLUDA is a selective radiotracer for in vivo imaging of the adenosine A2A receptor (A2AR) by positron emission tomography (PET). Promising preclinical results obtained by neuroimaging of mice and piglets suggest the translation of [18F]FLUDA to human PET studies. Thus, we report herein a remotely controlled automated radiosynthesis of [18F]FLUDA using a GE TRACERlab FX2 N radiosynthesizer. The radiotracer was obtained by a one-pot two-step radiofluorination procedure with a radiochemical yield of 9 ± 1%, a radiochemical purity of ≥ 99% and molar activities in the range of 69 333 GBq/µmol at the end of synthesis within a total synthesis time of approx. 95 min (n = 16). Altogether, we successfully established a reliable and reproducible procedure for the automated production of [18F]FLUDA.

A2A adenosine receptors (A2A-AR) have a cardio-protective function upon ischemia and reperfusion, but on the other hand, their stimulation could lead to arrhythmias. Our aim was to investigate the potential use of the PET radiotracer [18F]FLUDA to determine the A2A-AR availability non-invasively for diagnosis of the A2AR status. Therefore, we compared mice with a cardiomyocyte-specific overexpressing of the human A2A-AR (A2A-AR TG) with the respective wild type (WT). We determined: (1) the functional impact of FLUDA on the contractile function of atrial mouse samples, (2) the binding parameters (Bmax and KD) of [18F]FLUDA on mouse and additionally on human atrial tissue samples by autoradiographic studies, and investigated (3) the in vivo uptake of the radiotracer by dynamic PET imaging in the two A2A-AR TG and WT. After A2A-AR stimulation by CGS 21680 in isolated atrial preparations antagonistic effects of FLUDA were found in A2A-AR-TG animals but not in WT mice. Radiolabeled [18F]FLUDA exhibited a KD of 5.9 ± 1.6 nM and a Bmax of 455 ± 78 fmol/mg protein in cardiac samples of A2A-AR TG, whereas in WT, as well as in human atrial preparations only low specific binding could was found. Dynamic PET studies revealed a significantly higher initial uptake of [18F]FLUDA into the myocardium of A2A-AR TG compared to WT. The hA2A-AR-specific binding of [18F]FLUDA in vivo was verified by pre-administration of the highly affine A2AAR-specific antagonist istradefylline. Conclusion: [18F]FLUDA is a promising PET probe for the non-invasive assessment of the A2A-AR as a marker for pathologies linked to an increased A2A-AR density in the heart, as shown in patients with heart failure.

The cerebral expression of the A2A adenosine receptor (A2AAR) is altered in neurodegenerative disorders diseases such as Parkinson's (PD) or Huntington’s (HD) diseases, making these recep-tors an attractive diagnostic and therapeutic target. We aimed to further investigate the pharma-cokinetic properties in the brain of our recently developed A2AAR specific antagonist radioligand [18F]FLUDA. For this purpose, we retrospectively analysed dynamic PET studies of healthy mice and rotenone-treated mice, and undertook dynamic PET studies with healthy pigs. We performed analysis of mouse brain time-activity curves to calculate the mean residence time (MRT) by non-compartmental analysis and the binding potential (BPND) of [18F]FLUDA using the simplified reference tissue model (SRTM). For the pig studies, we performed a Logan graphical analysis to calculate the radiotracer distribution volume (VT) at baseline and under blocking conditions with tozadenant. The MRT of [18F]FLUDA in the striatum of mice was decreased by 30 % after treatment with the A2AAR antagonist, istradefylline. Mouse results showed the highest BPND (3.9 to 5.9) in the striatum. SRTM analysis showed a 20% lower A2AAR availability in the rotenone-treated mice compared to the control-aged group. Tozadenant treatment significantly decreased the VT (14.6 vs. 8.5 mL · g-1) and BPND values (1.3 vs. 0.3) in pig striatum. This study confirms the target specificity and a high BPND of [18F]FLUDA in the striatum. We conclude that [18F]FLUDA is a suitable tool for the non-invasive quantitation by PET of altered A2AAR expression in neurodegenerative diseases such as PD and HD.

The cannabinoid receptor type 2 (CB2R) is an attractive target for diagnosis and therapy of neurodegenerative diseases and cancer. Recently, we reported a novel naphthyrid-2-one based positron-emission tomography (PET) radioligand for imaging of the CB2R in the brain ([18F]5). In this study we aimed at the development of a novel 18F-labeled CB2R radioligand with improved binding properties and metabolic stability. Starting from the structure of 5, we developed a novel series of fluorinated derivatives by modifying the substituents at the naphthyrid-2-one subunit. Compound 28 (LU13) was identified with the highest binding affinity and selectivity versus CB1R (CB2RKi = 0.6 nM; CB1RKi/CB2RKi > 1000) and was selected for radiolabeling with 18F and biological characterization. The radiofluorination was performed starting from the corresponding bromo-precursor (31) bearing a fully deuterated N-alkyl chain to protect against defluorination. The in vitro evaluation of [18F]LU13 proved the high binding affinity of the radioligand towards rat (rCB2RKD = 0.2 nM) and human (hCB2RKD = 1.1 nM) CB2R. Metabolism studies in mice revealed a metabolic stability at 30 min p.i. with fractions of parent compound of >80% in the brain and 90% in the spleen with only trace of defluorination products detected in plasma. PET imaging in a rat model of vector-based/related overexpression in the striatum revealed a high signal to background ratio, demonstrating the ability of [18F]LU13 to reach and selectively label the hCB2R in the brain. Thus, [18F]LU13 is a novel and highly promising PET radioligand for the imaging of up regulated CB2R expression under pathological conditions in the brain.

The cannabinoid receptor type 2 (CB2R) is an attractive target for diagnosis and therapy of neurodegenerative diseases and cancer. Recently, we reported a novel naphthyrid-2-one based positron-emission tomography (PET) radioligand for imaging of the CB2R in the brain ([18F]5). In this study we aimed at the development of a novel 18F-labeled CB2R radioligand with improved binding properties and metabolic stability. Starting from the structure of 5, we developed a novel series of fluorinated derivatives by modifying the substituents at the naphthyrid-2-one subunit. Compound 28 (LU13) was identified with the highest binding affinity and selectivity versus CB1R (CB2RKi = 0.6 nM; CB1RKi/CB2RKi > 1000) and was selected for radiolabeling with 18F and biological characterization. The radiofluorination was performed starting from the corresponding bromo-precursor (31) bearing a fully deuterated N-alkyl chain to protect against defluorination. The in vitro evaluation of [18F]LU13 proved the high binding affinity of the radioligand towards rat (rCB2RKD = 0.2 nM) and human (hCB2RKD = 1.1 nM) CB2R. Metabolism studies in mice revealed a metabolic stability at 30 min p.i. with fractions of parent compound of >80% in the brain and 90% in the spleen with only trace of defluorination products detected in plasma. PET imaging in a rat model of vector-based/related overexpression in the striatum revealed a high signal to background ratio, demonstrating the ability of [18F]LU13 to reach and selectively label the hCB2R in the brain. Thus, [18F]LU13 is a novel and highly promising PET radioligand for the imaging of up regulated CB2R expression under pathological conditions in the brain.

PET data, mice; i.v. administration of [18F]FLUDA with and without pre-administration of istradefylline

The cannabinoid receptor type 2 (CB2R) is an attractive target for diagnosis and therapy of neurodegenerative diseases and cancer. Recently, we reported a novel naphthyrid-2-one based positron-emission tomography (PET) radioligand for imaging of the CB2R in the brain ([18F]5). In this study we aimed at the development of a novel 18F-labeled CB2R radioligand with improved binding properties and metabolic stability. Starting from the structure of 5, we developed a novel series of fluorinated derivatives by modifying the substituents at the naphthyrid-2-one subunit. Compound 28 (LU13) was identified with the highest binding affinity and selectivity versus CB1R (CB2RKi = 0.6 nM; CB1RKi/CB2RKi > 1000) and was selected for radiolabeling with 18F and biological characterization. The radiofluorination was performed starting from the corresponding bromo-precursor (31) bearing a fully deuterated N-alkyl chain to protect against defluorination. The in vitro evaluation of [18F]LU13 proved the high binding affinity of the radioligand towards rat (rCB2RKD = 0.2 nM) and human (hCB2RKD = 1.1 nM) CB2R. Metabolism studies in mice revealed a metabolic stability at 30 min p.i. with fractions of parent compound of >80% in the brain and 90% in the spleen with only trace of defluorination products detected in plasma. PET imaging in a rat model of vector-based/related overexpression in the striatum revealed a high signal to background ratio, demonstrating the ability of [18F]LU13 to reach and selectively label the hCB2R in the brain. Thus, [18F]LU13 is a novel and highly promising PET radioligand for the imaging of up regulated CB2R expression under pathological conditions in

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 mouse and pig brain. In vivo evaluation in mice revealed improved stability of [18F]FLUDA compared to [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.

Monoamine oxidases (MAOs) play a key role in the metabolism of major monoamine neurotransmitters. In particular, the upregulation of MAO-B in Parkinson’s disease, Alzheimer’s disease and cancer augmented the development of selective MAO-B inhibitors for diagnostic and therapeutic purposes, such as the anti-parkinsonian MAO-B irreversible binder L-deprenyl (Selegiline®). Herein we report on the synthesis of novel fluorinated indanone derivatives for PET imaging of MAO-B in the brain. Out of our series, the derivatives 6, 8, 9 and 13 are amongst the most affine and selective ligands for MAO-B reported so far. For the derivative 6-((3-fluorobenzyl)oxy)-2,3-dihydro-1H-inden-1-one (6) exhibiting an outstanding affinity (Ki MAO-B = 6 nM), an automated copper-mediated radiofluorination starting from the pinacol boronic ester 17 is described. An in vitro screening in different species revealed a MAO-B region-specific accumulation of [18F]6 in rats and piglets in comparison to L-[3H]deprenyl. The pre-clinical in vivo assessment of [18F]6 in mice demonstrated the potential of indanones to readily cross the blood-brain barrier. Nonetheless, parallel in vivo metabolism studies indicated the presence of blood-brain barrier metabolites, thus arguing for further structural modifications. With the matching analytical profiles of the radiometabolite analysis from the in vitro liver microsome studies and the in vivo evaluation, the structure’s elucidation of the blood-brain barrier penetrant radiometabolites is possible and will serve as basis for the development of new indanone derivatives suitable for the PET imaging of MAO-B.

The adenosine A2A receptor (A2AR) has emerged as a potential non-dopaminergic target for the treatment of Parkinson’s disease and thus, the non-invasive imaging with positron emission tomography (PET) is of utmost importance to monitor the receptor expression and occupancy during an A2AR-tailored therapy. Aiming at the development of a PET radiotracer, we herein report the design of a series of novel fluorinated analogs based on the structure of the A2AR antagonist tozadenant, and the preclinical evaluation of [18F]TOZ1. Autoradiography proved A2AR-specific in vitro binding of [18F]TOZ1 to striatum of mouse and pig brain. Investigations of the metabolic stability in mice revealed parent fractions of more than 76% and 92% of total activity in plasma and brain samples, respectively. Dynamic PET/magnetic resonance imaging (MRI) studies in mice revealed a brain uptake but no A2AR-specific in vivo binding.

The adenosine A2A receptor (A2AR) represents a potential therapeutic target for neurodegenerative diseases. Aiming at the development of a positron emission tomography (PET) radiotracer to monitor changes of receptor density and/or occupancy during the A2AR-tailored therapy, we designed a library of fluorinated analogs based on a recently published lead compound. Among those, the highly affine 4-fluorobenzyl derivate (PPY1; Ki(hA2AR) = 5.3 nM) and the 2-fluorobenzyl derivate (PPY2; Ki(hA2AR) = 2.1 nM) were chosen for 18F-labeling via an alcohol-enhanced copper-mediated procedure starting from the corresponding boronic acid pinacol ester precursors. Investigations of the metabolic stability of [18F]PPY1 and [18F]PPY2 in CD-1 mice by radio-HPLC analysis revealed parent fractions of more than 76% of total activity in the brain. Specific binding of [18F]PPY2 on mice brain slices was demonstrated by in vitro autoradiography. In vivo PET/magnetic resonance imaging (MRI) studies in CD-1 mice revealed a reasonable high initial brain uptake for both radiotracers, followed by a fast clearance.

Bei diesem Datensatz handelt es sich um HPLC-Daten von den Radiosynthesen von [18F]FLUDA.

Introduction The A2AR has emerged as a potential therapeutic target due to its involvement in basic functions of the neuronal, cardiovascular and immune systems. Blockade of A2AR is regarded as potential tool related to CAR T-cell immunotherapy of cancer. Furthermore, A2AR are believed to regulate myocardial oxygen demand and to increase coronary circulation by vasodilation. With regard to Parkinson’s disease A2AR antagonists, such as the FDA approved Nourianz®, are used as an adjunctive treatment to levopoda®. Therefore noninvasive imaging to monitor changes of receptor density and/or occupancy during the A2aR-tailored therapy is of utmost importance. We recently developed the A2AR PET radiotracer [18F]FLUDA which demonstrated superior pharmacokinetic properties among the radiotracers available. Towards its clinical translation, an automated radiosynthesis was developed and the radiotracer was fully characterized in vitro and in vivo including toxicity and dosimetry1 studies. Methods The binding affinity (Ki) of FLUDA towards the human A2AR and A1R subtypes was estimated in vitro by competitive radioligand binding assays. In addition, selectivity studies were performed. An automated two-step one-pot radiosynthesis of [18F]FLUDA was developed. In vitro autoradiography was performed on cryosections of mice brain. Dynamic PET/MR studies under baseline and blocking conditions were assessed. The time-activity curves of the SUV ratio (SUVR) of striatum over cerebellum were used as measure for specific uptake. Metabolism was investigated in CD-1 mice via radio-HPLC analysis of extracted plasma and brain samples. Single-dose acute toxicity of FLUDA was assessed in male and female Wistar rats. Results A high A2aR binding affinity and high A1R selectivity were recorded for FLUDA (KiA2aR= 0.60 nM and KiA1R= XX nM). The two-step one-pot automated radiosynthesis of [18F]FLUDA was successfully established (radiochemical yield: 9±1%; radiochemical purity: ≥98%; molar activity= 69

Introduction The A2AR has emerged as a potential therapeutic target due to its involvement in basic functions of the neuronal, cardiovascular and immune systems. Blockade of A2AR is regarded as potential tool related to CAR T-cell immunotherapy of cancer. Furthermore, A2AR are believed to regulate myocardial oxygen demand and to increase coronary circulation by vasodilation. With regard to Parkinson’s disease A2AR antagonists, such as the FDA approved Nourianz®, are used as an adjunctive treatment to levopoda®. Therefore noninvasive imaging to monitor changes of receptor density and/or occupancy during the A2aR-tailored therapy is of utmost importance. We recently developed the A2AR PET radiotracer [18F]FLUDA which demonstrated superior pharmacokinetic properties among the radiotracers available. Towards its clinical translation, an automated radiosynthesis was developed and the radiotracer was fully characterized in vitro and in vivo including toxicity and dosimetry1 studies. Methods The binding affinity (Ki) of FLUDA towards the human A2AR and A1R subtypes was estimated in vitro by competitive radioligand binding assays. In addition, selectivity studies were performed. An automated two-step one-pot radiosynthesis of [18F]FLUDA was developed. In vitro autoradiography was performed on cryosections of mice brain. Dynamic PET/MR studies under baseline and blocking conditions were assessed. The time-activity curves of the SUV ratio (SUVR) of striatum over cerebellum were used as measure for specific uptake. Metabolism was investigated in CD-1 mice via radio-HPLC analysis of extracted plasma and brain samples. Single-dose acute toxicity of FLUDA was assessed in male and female Wistar rats. Results A high A2aR binding affinity and high A1R selectivity were recorded for FLUDA (KiA2aR= 0.60 nM and KiA1R= XX nM). The two-step one-pot automated radiosynthesis of [18F]FLUDA was successfully established (radiochemical yield: 9±1%; radiochemical purity: ≥98%; molar activity= 69

Adenosine is an essential neuromodulatory molecule that acts via four G-protein coupled receptors (A1R, A2AR, A2BR, A3R). In the central nervous system (CNS), the A2AR is highly concentrated in the striatum. The A2AR is a promising target for positron emission tomography (PET) imaging of neurodegenerative diseases, such as Huntington’s disease (HD), Alzheimer’s disease (AD) and Parkinson’s disease (PD). Istradefylline is the first A2AR antagonist that is approved by the U.S. Food and Drug Administration (FDA) for adjunctive treatment in patients with PD. So far, [18F]MNI-444 [Ki (hA2AR) = 2.8 nM] is the only 18F-labelled A2AR radiotracer evaluated in healthy subjects. Aiming at the development of A2AR radiotracers with improved molecular imaging properties, this study is based on three recently published lead compounds with a pyrazolo[3,4-d]pyridine, a morpholinobenzo[d]thiazol-2-amine and a pyrazolo[4,3‑e]‑1,2,4-triazolo[1,5‑ c]-pyrimidine scaffold. Herein, a series of 30 fluorinated derivatives was developed by systematic modification of selected lead compounds. The binding affinities torwards the A2AR and the adenosine A1 receptor (A1R) subtypes were determined by in vitro radioligand binding assays. Regarding the binding affinity and selectivity, PYP1 [Ki (hA2AR) = 5.29 nM, Ki (hA1R) = 220 nM)], PYP2 [Ki (hA2AR) = 2.13 nM, Ki (hA1R) = 147 nM)] und TOZ1 [Ki (hA2AR) = 1.00 nM, Ki (hA1R) = 618 nM)] were radiolabelled as the most suitable A2AR ligands in order to perform first preclinical studies in mice. Additionally, FLUDA [Ki (hA2AR) = 0.61 nM, Ki (hA1R) = 767 nM] was developed and radiolabelled based on the known PET radiotracer [18F]FESCH. [18F]FESCH was selected as reference compound and thus, its radio-synthesis was established as well as optimised in our laboratories. Three different labelling strategies have been investigated in the frame of this work: (i) two-step one-pot radiolabelling procedures using 18F-labelled prosthetic groups, (ii) alcohol-enhanced

Introduction: The monoamine oxidase B (MAO B) isoenzyme is known to be involved in the oxidative deamination of biogenic amines. While the use of MAO B inhibitors is already well-established for the treatment of Parkinson’s disease, recent reports suggest its involvement in certain types of brain tumors.1 We herein aim at the synthesis and preclinical evaluation of fluorinated indanone-based derivatives targeting MAO B in the brain via positron emission tomography (PET). Methods: A small series of fluorinated indanone derivatives was obtained via the O-alkylation or esterification starting with the commercially available 6-hydroxy-2,3-dihydro-1H-inden-1-one in two steps. Binding affinities towards the human MAO isoenzymes were estimated in vitro by radioligand displacement. HL126 was selected for radiofluorination via its corresponding boronic acid pinacol ester. In vitro autoradiography of [18F]HL126 was performed in mice brain slices. In vivo evaluation of [18F]HL126 in CD-1 mice was carried out and metabolism studies were performed in plasma and brain samples via radio-HPLC. Results: The fluorinated indanone derivatives were synthesized in yields ranging from 65-89%. The fluorophenyl ether derivative, HL126, was further selected for radiofluorination based on its high binding affinity towards MAO B (Ki = 6.9 ± 5.33 nM). [18F]HL126 was obtained by an alcohol-enhanced copper-mediated approach via the corresponding boronic acid pinacol ester precursor with radiochemical yields of about 11 ± 3%, high radiochemical purities (≥99%) and molar activities in the range of 20 GBq/mol. In vitro autoradiography showed a specific blockade with selective MAO-A/B inhibitors. PET/MRI analyses revealed that [18F]HL126 readily enters the brain. Some radiometabolites do cross the blood-brain barrier. Conclusion: Although metabolism studies with [18F]HL126 revealed the presence of radiometabolites in the brain, the high binding affinity towards MAO B and the pronounced selectivity i

A2AR-Liganden sind bei ischämischen Reperfusionsschäden kardioprotektiv wirksam (1). Somit ist eine Diagnose der kardialen A2AR-Verfügbarkeit für die Behandlung von Patienten mit koronaren Erkrankungen bedeutsam. Unser Ziel war es, anhand eines transgenen Mausmodells mit einer kardialen Überexpression des humanen A2AR das Potential von [18F]FLUDA als potentielles Radiopharmakon für die Darstellung des A2AR zu evaluieren. Es wurden 4-6 Monate alte FVB/N Mäuse mit einer Kardiomyozyten-spezifischen Überexpression des humanen A2AR (A2AR TG) bzw. Kontrolltiere untersucht. Die Bestimmung der KD- und Bmax-Werte von [18F]FLUDA erfolgte autoradiographisch an Kryoschnitten von Herzexplantaten. Die In-vivo-Untersuchungen fanden unter Isoflurannarkose in einem Kleintier-PET/MRT-Scanner (nanoscan, Mediso) statt. [18F]FLUDA (7,4±3,4 MBq) wurde i.v. über die Schwanzvene 20 s nach Start der 90-minütigen PET-Messung appliziert. Die A2AR-Spezifität von [18F]FLUDA wurde durch Applikation von 2,5 mg/kg Tozadenant 10 min vor der Tracer Gabe bestimmt. Für die anatomische Korrelation und Schwächungskorrektur der PET-Aufnahmen erfolgte eine T1-gewichtete MRT. Die dynamische Rekonstruktion der Listenmodus-Daten erfolgte durch einen 3D-OSEM-Algorithmus. Die Quantifizierung der aufgenommenen Aktivität erfolgte mit PMOD. Mittels In-vitro-Autoradiografie von [18F]FLUDA konnten in den A2AR-TG Herzen die Rezeptorparameter KD (5,9 ± 1,6 nM) und Bmax (455 ± 78 fmol/mg Protein) bestimmt werden, während in den Herzen der Kontroll-Tiere die Rezeptordichte unter der Nachweisgrenze lag. Mittels PET/MR wurde 15–30 min p.i. für die A2A-R TG Tiere ein SUV-Verhältnis (SUVR) Myokard/Herzventrikel von ≥1,0 bestimmt. Tozadenant verminderte das SUVR um 6 % (p < 0.05). [18F]FLUDA ist ein vielversprechender Radiotracer zur Untersuchung der A2AR Verfügbarkeit im Herzen. (1) Boknik P, et al., Front Pharmacol. 2018; 9:1–12.

Question We have shown that A2A adenosine receptors (A2A-AR) are functionally active in human hearts. Moreover, we generated a transgenic mouse model with heart specific overexpression of the human A2A-AR (TG), which responded to agonists with a positive inotropic effect in vitro. Overexpressed A2A-AR were cardioprotective but also proarrhythmic in TG (Boknik et al. Front Pharmacol 2018, 2019). Here, we focused on the question if a cardiac A2A-AR expression could be assessed in vivo utilizing PET imaging in this model. Methods The impact of FLUDA (7-(3-(4-(2-(fluoro)ethoxy-1,1,2,2-d4)phenyl)propyl)-2-(furan-2-yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine; patent: DE 10 2019 116 986.0) on the force of contraction (FOC) in isolated electrically driven (1 Hz) atrial preparation after stimulation with the A2A–AR-agonist CGS 2180 (10 µM, in the presence of the A1A-AR antagonist DPCPX 1 µM) was measured. On cryosections of mouse hearts the KD and Bmax values of [18F]FLUDA were determined by autoradiography. A small animal PET/MRI scanner (nanoscan, Mediso) was used for in vivo imaging of mice under isoflurane anaesthesia. [18F]FLUDA (7.4±3.4 MBq) was applied via the tail vein 20 s after starting the 90-minute PET measurement. A2A-AR specificity of [18F]FLUDA was determined by application of 2.5 mg/kg body weight Tozadenant 10 minutes prior to tracer administration. Results FLUDA was able to reduce (p<0.05) the increase of FOC after CGS 2180 stimulation by about 20 % (p<0.05) in isolated electrically driven atrial preparation in TG (but not WT), indicating a functional antagonism of FLUDA at the human cardiac A2A-AR. By in vitro autoradiography of [18F]FLUDA a KD (5.9±1.6 nM) and Bmax (455±78 fmol/mg protein) could be determined in the A2A-AR-TG hearts, whereas in the control hearts the receptor density was below the detection limit. Using PET/MR, an SUV ratio (SUVR) myocardial/cardiac ventricle of ≥1,0 was determined for the A2A-AR-TG animals at 15-30 min

Der Adenosin-A2A-Rezeptor (A2AR) ist ein vielversprechendes Target für die molekulare Bildgebung sowohl von neurodegenerativen Erkrankungen als auch von Tumoren mittels PET. Bis zum jetzigen Zeitpunkt ist [18F]MNI 444 [Ki(hA2AR) = 2,8 nM] der einzige 18F-markierte Radiotracer, welcher in einer klinischen Studie an gesunden Probanden untersucht wurde (1). Ausgehend von dem literaturbekannten [18F]FESCH [Ki(hA2AR) = 0,6 nM] sollte durch chemische Modifikation ein deuteriertes Analogon mit einer erhöhter metabolischer Stabilität entwickelt werden (2,3). Die Synthese von FLUDA basiert auf der Einführung einer deuterierten Fluoroethoxy-Gruppe. Für die Radiosynthese von [18F]FLUDA wurde eine zweistufige Eintopfmethode ausgehend von einem Phenol- und [2H4]Ethylenditosylat-Präkursor entwickelt. Die In vitro- und In-vivo-Evaluierung erfolgte mittels Autoradiographie-, Metaboliten- und PET-Studien in CD-1 Mäusen. Es wurde eine Radiosynthese von [18F]FLUDA [Ki(hA2AR) = 0,6 nM] mit einer radiochemischen Ausbeute von 19±3% (n = 9) etabliert. Im Vergleich zu [18F]FESCH zeigt das deuterierte [18F]FLUDA eine deutlich gesteigerte In-vivo-Stabilität (15 min p.i., Gehirn: 91% intaktes [18F]FLUDA). Die In-vitro-Autoradiographie von [18F]FLUDA weist eine spezifische Aktivitätsanreicherung im Striatum nach, die durch die Rezeptorparameter KD = 4,3±0,7 nM und Bmax = 556±143 fmol/mg charakterisiert ist. In den PET-Studien wurde ein SUV-Verhältnis (SUVR) Striatum/Cerebellum von >8 (15-30 min) nachgewiesen. Selektive A2AR-Blockadestudien mit 2,5 mg/kg Tozadenant führten zu einem signifikanten Rückgang dieses SUVR um 35%. Die Radiosynthese des neuen Radiotracers [18F]FLUDA wurde erfolgreich etabliert. Aufgrund der vielversprechenden präklinischen Ergebnisse wird derzeit die Translation von [18F]FLUDA in die Klinik vorbereitet. (1) Barret et al., J Nucl Med 2015, 56, 586-91 (2) Bhattacharjee et al., Nucl Med Biol 2011, 38, 897-906 (3) Khanapur et al., J Med Chem 2014, 57, 6765-80

Herein, we report on the synthesis and pharmacological evaluation of ten novel fluorinated cinnamylpiperazines as potential monoamine oxidase B (MAO-B) ligands. The designed derivatives consist of either cinnamyl or 2-fluorocinnamyl moieties connected to 2-fluoropyridylpiperazines. The three-step synthesis starting from commercially available piperazine afforded the final products in overall yields between 9 and 29%. An in vitro competitive binding assay using L-[3H]Deprenyl as radioligand was developed and the MAO-B binding affinities of the synthesized derivatives were assessed. Docking studies revealed that the compounds 8–17 were stabilized in both MAO-B entrance and substrate cavities, thus resembling the binding pose of L-Deprenyl. Although our results revealed that the novel fluorinated cinnamylpiperazines 8–17 do not possess sufficient MAO-B binding affinity to be eligible as positron emission tomography (PET) agents, the herein developed binding assay and the insights gained within our docking studies will certainly pave the way for further development of MAO-B ligands.

The adenosine A2A receptor (A2AR) is regarded as a particularly appropriate target for non-dopaminergic treatment of Parkinson’s disease (PD). An increased A2AR availability has been found in the human striatum at early stages of PD and in patients with PD and dyskinesias. The aim of this small animal positron emission tomography/magnetic resonance (PET/MR) imaging study was to investigate whether rotenone-treated mice reflect the aspect of striatal A2AR upregulation in PD. For that purpose, we selected the known A2AR-specific radiotracer [18F]FESCH and developed a simplified two-step one-pot radiosynthesis. PET images showed a high uptake of [18F]FESCH in the mouse striatum. Concomitantly, metabolism studies with [18F]FESCH revealed the presence of a brain-penetrant radiometabolite. In rotenone-treated mice, a slightly higher striatal A2AR binding of [18F]FESCH was found. Nonetheless, the correlation between the increased A2AR levels within the proposed PD animal model remains to be further investigated.

Introduction: The monoamine oxidase B (MAO B) isoenzyme is known to be involved in the oxidative deamination of biogenic amines. While the use of MAO B inhibitors is already well-established for the treatment of Parkinson’s disease, recent reports suggest its involvement in certain types of brain tumors.1 We herein aim at the synthesis and preclinical evaluation of fluorinated indanone-based derivatives targeting MAO B in the brain via positron emission tomography (PET). Methods: A small series of fluorinated indanone derivatives was obtained via the O-alkylation or esterification starting with the commercially available 6-hydroxy-2,3-dihydro-1H-inden-1-one in two steps. Binding affinities towards the human MAO isoenzymes were estimated in vitro by radioligand displacement. HL126 was selected for radiofluorination via its corresponding boronic acid pinacol ester. In vitro autoradiography of [18F]HL126 was performed in mice brain slices. In vivo evaluation of [18F]HL126 in CD-1 mice was carried out and metabolism studies were performed in plasma and brain samples via radio-HPLC. Results: The fluorinated indanone derivatives were synthesized in yields ranging from 65-89%. The fluorophenyl ether derivative, HL126, was further selected for radiofluorination based on its high binding affinity towards MAO B (Ki = 6.9 ± 5.33 nM). [18F]HL126 was obtained by an alcohol-enhanced copper-mediated approach via the corresponding boronic acid pinacol ester precursor with radiochemical yields of about 11 ± 3%, high radiochemical purities (≥99%) and molar activities in the range of 20 GBq/mol. In vitro autoradiography showed a specific blockade with selective MAO-A/B inhibitors. PET/MRI analyses revealed that [18F]HL126 readily enters the brain. Some radiometabolites do cross the blood-brain barrier. Conclusion: Although metabolism studies with [18F]HL126 revealed the presence of radiometabolites in the brain, the high binding affinity towards MAO B and the pronounced selectivity i

Question We have shown that A2A adenosine receptors (A2A-AR) are functionally active in human hearts. Moreover, we generated a transgenic mouse model with heart specific overexpression of the human A2A-AR (TG), which responded to agonists with a positive inotropic effect in vitro. Overexpressed A2A-AR were cardioprotective but also proarrhythmic in TG (Boknik et al. Front Pharmacol 2018, 2019). Here, we focused on the question if a cardiac A2A-AR expression could be assessed in vivo utilizing PET imaging in this model. Methods The impact of FLUDA (7-(3-(4-(2-(fluoro)ethoxy-1,1,2,2-d4)phenyl)propyl)-2-(furan-2-yl)-7H-pyrazolo[4,3-e][1,2,4]triazolo[1,5-c]pyrimidin-5-amine; patent: DE 10 2019 116 986.0) on the force of contraction (FOC) in isolated electrically driven (1 Hz) atrial preparation after stimulation with the A2A–AR-agonist CGS 2180 (10 µM, in the presence of the A1A-AR antagonist DPCPX 1 µM) was measured. On cryosections of mouse hearts the KD and Bmax values of [18F]FLUDA were determined by autoradiography. A small animal PET/MRI scanner (nanoscan, Mediso) was used for in vivo imaging of mice under isoflurane anaesthesia. [18F]FLUDA (7.4±3.4 MBq) was applied via the tail vein 20 s after starting the 90-minute PET measurement. A2A-AR specificity of [18F]FLUDA was determined by application of 2.5 mg/kg body weight Tozadenant 10 minutes prior to tracer administration. Results FLUDA was able to reduce (p<0.05) the increase of FOC after CGS 2180 stimulation by about 20 % (p<0.05) in isolated electrically driven atrial preparation in TG (but not WT), indicating a functional antagonism of FLUDA at the human cardiac A2A-AR. By in vitro autoradiography of [18F]FLUDA a KD (5.9±1.6 nM) and Bmax (455±78 fmol/mg protein) could be determined in the A2A-AR-TG hearts, whereas in the control hearts the receptor density was below the detection limit. Using PET/MR, an SUV ratio (SUVR) myocardial/cardiac ventricle of ≥1,0 was determined for the A2A-AR-TG animals at 15-30 min

Die Erfindung betrifft eine Verbindung der allgemeinen Formel I (Formel I) worin Ar eine Phenylgruppe oder eine Pyridylgruppe ist; R1 Wasserstoff oder eine Nitrogruppe ist; und R2 Fluor oder eine Abgangsgruppe ist, wobei die Abgangsgruppe aus der Gruppe ausgewählt ist, die aus einer Nitrogruppe, einem Halogen, einem Diazoniumion oder -salz, einem Trialkylammoniumion oder -salz, einem Dialkoxyaren, einem Sulfoxid, einer Boronsäure, einem Boronsäureester, Alkylzinn, Arylzinn, einem Iodoniumion oder -salz, einem Iodonium-Ylid und einem Sulfonsäureester besteht.

Die Erfindung betrifft eine Verbindung der allgemeinen Formel I worin die Reste X1a, X1b, X2a, X2b, X3a, X3b, X4a, X4b, X5a und X5b unabhängig voneinander jeweils Wasserstoff oder Deuterium sind, mit der Maßgabe, dass zumindest einer der Reste X1a, X1b, X2a, X2b, X3a, X3b, X4a, X4b, X5a und X5b Deuterium ist.

A2AR-Liganden sind bei ischämischen Reperfusionsschäden kardioprotektiv wirksam (1). Somit ist eine Diagnose der kardialen A2AR-Verfügbarkeit für die Behandlung von Patienten mit koronaren Erkrankungen bedeutsam. Unser Ziel war es, anhand eines transgenen Mausmodells mit einer kardialen Überexpression des humanen A2AR das Potential von [18F]FLUDA als potentielles Radiopharmakon für die Darstellung des A2AR zu evaluieren. Es wurden 4-6 Monate alte FVB/N Mäuse mit einer Kardiomyozyten-spezifischen Überexpression des humanen A2AR (A2AR TG) bzw. Kontrolltiere untersucht. Die Bestimmung der KD- und Bmax-Werte von [18F]FLUDA erfolgte autoradiographisch an Kryoschnitten von Herzexplantaten. Die In-vivo-Untersuchungen fanden unter Isoflurannarkose in einem Kleintier-PET/MRT-Scanner (nanoscan, Mediso) statt. [18F]FLUDA (7,4±3,4 MBq) wurde i.v. über die Schwanzvene 20 s nach Start der 90-minütigen PET-Messung appliziert. Die A2AR-Spezifität von [18F]FLUDA wurde durch Applikation von 2,5 mg/kg Tozadenant 10 min vor der Tracer Gabe bestimmt. Für die anatomische Korrelation und Schwächungskorrektur der PET-Aufnahmen erfolgte eine T1-gewichtete MRT. Die dynamische Rekonstruktion der Listenmodus-Daten erfolgte durch einen 3D-OSEM-Algorithmus. Die Quantifizierung der aufgenommenen Aktivität erfolgte mit PMOD. Mittels In-vitro-Autoradiografie von [18F]FLUDA konnten in den A2AR-TG Herzen die Rezeptorparameter KD (5,9 ± 1,6 nM) und Bmax (455 ± 78 fmol/mg Protein) bestimmt werden, während in den Herzen der Kontroll-Tiere die Rezeptordichte unter der Nachweisgrenze lag. Mittels PET/MR wurde 15–30 min p.i. für die A2A-R TG Tiere ein SUV-Verhältnis (SUVR) Myokard/Herzventrikel von ≥1,0 bestimmt. Tozadenant verminderte das SUVR um 6 % (p < 0.05). [18F]FLUDA ist ein vielversprechender Radiotracer zur Untersuchung der A2AR Verfügbarkeit im Herzen. (1) Boknik P, et al., Front Pharmacol. 2018; 9:1–12.

Introduction The adenosine A2A receptor (A2AR) is related to the pathogenesis of several brain diseases and is assumed to mediate immunsuppressive processes related to cancer pathology. Thus, A2AR radiotracers for PET imaging are promising candidates for the differential diagnosis of neurodegenerative diseases, in particular Parkinson’s disease, and to study the A2AR within the tumor environment. We developed [18F]FLUDA based on the deuteration of the [18F]fluoroethoxy chain of [18F]FESCH [1,2] to improve imaging properties in mice. [18F]FLUDA was evaluated pre-clinically prior to a first-in-human trial. Methods Binding affinities of FLUDA towards the human A2AR and A1R subtypes were estimated in vitro by competitive radioligand binding assays. [18F]FLUDA was synthesized by a two-step one-pot approach. In vitro autoradiography of [18F]FLUDA was performed on mice brain cryosections. In vivo evaluation of [18F]FLUDA was carried out in a CD-1 mouse by radio-HPLC analysis of plasma and brain samples (15 min p.i.) and dynamic PET/MR studies under baseline (n = 4) and blocking conditions (2.5 mg tozadenant per kg, 15 min before tracer, n = 4). The cerebellum was used as a reference tissue. The time-activity curves were obtained and the SUV ratio (SUVR) of striatum over cerebellum were used as measure for specific uptake. Results/discussion In vitro binding studies revealed no influence of deuteration on the estimated binding affinities with Ki values of FLUDA and FESCH towards human A2AR of 0.60 nM and 0.61 nM, respectively. The radiosynthesis of [18F]FLUDA was successfully established (Fig.1). A single experiment indicates that [18F]FLUDA is metabolically more stable in mouse than [18F]FESCH. While no radiometabolites were found for [18F]FLUDA in plasma and brain samples at 15 min p.i., for [18F]FESCH the percentages of intact radiotracer were 71% and 41% in brain and plasma samples, respectively. By in vitro autoradiography [18F]FLUDA demonstrated a specific accumulatio

Der Adenosin-A2A-Rezeptor (A2AR) ist ein vielversprechendes Target für die molekulare Bildgebung sowohl von neurodegenerativen Erkrankungen als auch von Tumoren mittels PET. Bis zum jetzigen Zeitpunkt ist [18F]MNI 444 [Ki(hA2AR) = 2,8 nM] der einzige 18F-markierte Radiotracer, welcher in einer klinischen Studie an gesunden Probanden untersucht wurde (1). Ausgehend von dem literaturbekannten [18F]FESCH [Ki(hA2AR) = 0,6 nM] sollte durch chemische Modifikation ein deuteriertes Analogon mit einer erhöhter metabolischer Stabilität entwickelt werden (2,3). Die Synthese von FLUDA basiert auf der Einführung einer deuterierten Fluoroethoxy-Gruppe. Für die Radiosynthese von [18F]FLUDA wurde eine zweistufige Eintopfmethode ausgehend von einem Phenol- und [2H4]Ethylenditosylat-Präkursor entwickelt. Die In vitro- und In-vivo-Evaluierung erfolgte mittels Autoradiographie-, Metaboliten- und PET-Studien in CD-1 Mäusen. Es wurde eine Radiosynthese von [18F]FLUDA [Ki(hA2AR) = 0,6 nM] mit einer radiochemischen Ausbeute von 19±3% (n = 9) etabliert. Im Vergleich zu [18F]FESCH zeigt das deuterierte [18F]FLUDA eine deutlich gesteigerte In-vivo-Stabilität (15 min p.i., Gehirn: 91% intaktes [18F]FLUDA). Die In-vitro-Autoradiographie von [18F]FLUDA weist eine spezifische Aktivitätsanreicherung im Striatum nach, die durch die Rezeptorparameter KD = 4,3±0,7 nM und Bmax = 556±143 fmol/mg charakterisiert ist. In den PET-Studien wurde ein SUV-Verhältnis (SUVR) Striatum/Cerebellum von >8 (15-30 min) nachgewiesen. Selektive A2AR-Blockadestudien mit 2,5 mg/kg Tozadenant führten zu einem signifikanten Rückgang dieses SUVR um 35%. Die Radiosynthese des neuen Radiotracers [18F]FLUDA wurde erfolgreich etabliert. Aufgrund der vielversprechenden präklinischen Ergebnisse wird derzeit die Translation von [18F]FLUDA in die Klinik vorbereitet. (1) Barret et al., J Nucl Med 2015, 56, 586-91 (2) Bhattacharjee et al., Nucl Med Biol 2011, 38, 897-906 (3) Khanapur et al., J Med Chem 2014, 57, 6765-80

Adenosine is an essential neuromodulatory molecule that acts via four G-protein coupled receptors (A1R, A2AR, A2BR, A3R). In the central nervous system (CNS), the A2AR is highly concentrated in the striatum. The A2AR is a promising target for positron emission tomography (PET) imaging of neurodegenerative diseases, such as Huntington’s disease (HD), Alzheimer’s disease (AD) and Parkinson’s disease (PD). Istradefylline is the first A2AR antagonist that is approved by the U.S. Food and Drug Administration (FDA) for adjunctive treatment in patients with PD. So far, [18F]MNI-444 [Ki (hA2AR) = 2.8 nM] is the only 18F-labelled A2AR radiotracer evaluated in healthy subjects. Aiming at the development of A2AR radiotracers with improved molecular imaging properties, this study is based on three recently published lead compounds with a pyrazolo[3,4-d]pyridine, a morpholinobenzo[d]thiazol-2-amine and a pyrazolo[4,3‑e]‑1,2,4-triazolo[1,5‑ c]-pyrimidine scaffold. Herein, a series of 30 fluorinated derivatives was developed by systematic modification of selected lead compounds. The binding affinities torwards the A2AR and the adenosine A1 receptor (A1R) subtypes were determined by in vitro radioligand binding assays. Regarding the binding affinity and selectivity, PYP1 [Ki (hA2AR) = 5.29 nM, Ki (hA1R) = 220 nM)], PYP2 [Ki (hA2AR) = 2.13 nM, Ki (hA1R) = 147 nM)] und TOZ1 [Ki (hA2AR) = 1.00 nM, Ki (hA1R) = 618 nM)] were radiolabelled as the most suitable A2AR ligands in order to perform first preclinical studies in mice. Additionally, FLUDA [Ki (hA2AR) = 0.61 nM, Ki (hA1R) = 767 nM] was developed and radiolabelled based on the known PET radiotracer [18F]FESCH. [18F]FESCH was selected as reference compound and thus, its radio-synthesis was established as well as optimised in our laboratories. Three different labelling strategies have been investigated in the frame of this work: (i) two-step one-pot radiolabelling procedures using 18F-labelled prosthetic groups, (ii) alcohol-enhanced

Die Erfindung betrifft eine Verbindung der allgemeinen Formel I worin eine Phenylgruppe oder eine Pyridylgruppe ist, R1 aus der Gruppe ausgewählt ist, die aus Wasserstoff, Halogen und -CN besteht; R2 aus der Gruppe ausgewählt ist, die aus Fluor, einer fluorierten Alkylgruppe mit 1 bis 12 Kohlenstoffatomen, einer fluorierten Alkoxygruppe mit 1 bis 12 Kohlenstoffatomen und einer fluorierten Ethergruppe besteht; Z -(CH2)n- oder -(CH2)m-C(O)-(CH2)p- ist, wobei n eine Ganzzahl von 1 bis 12 ist und wobei m und p gleich oder verschieden sein können und jeweils 0 oder eine Ganzzahl von 1 bis 12 sind.