Semi-automated synthesis, validation and microPET imaging of 18F-FP-DTBZ as a vesicular monoamine transporter ligand

This work was to develop a semi-automated synthesis of 18F-9-fluoropropyl-9-desmethyl-DTBZ (18F-FP-DTBZ) and validate its potential as a vesicular monoamine transporter 2 (VMAT2) ligand.18F-FP-DTBZ was synthesized by a semi-automated procedure in a 21-35% yield without decay correction and with a radiochemical purity of >98%.Bioistribution in rats exhibited a favorable brain uptakes of the ligand (0.31±0.04 ID% at 60min post injection,n=8).The highest radioactivity located in VMAT2 enriched striatal tissue.The target-to-nontarget ratio (striatum/cerebellum,ST/CB) was 4.81±0.84.Blocking studies implied that striatum uptake could be blocked by DTBZ (a VMAT2 inhibitor) but could not by CFT (a dopamine transporter inhibitor).MicroPET imaging with 18F-FP-DTBZ in normal rats gave high quality images in which high radioactivity were observed in the striatal tissue.Time-and-activity curves revealed good retention in the target (striatum) and rapid clearance in the background (cerebellum),which resulted in a maximum ST/CB ratio of 5.08±0.81 (n=3) in 80-120min.By contrast,the 6-hydroxydopamine unilateral lesioned rats gave asymmetrical striata images with higher 18F-FP-DTBZ concentration on the unlesioned side (unlesioned-ST/CB=5.21±0.38,n=3) than the lesioned (lesioned-ST/CB=2.34±0.51).The results validated that 18F-FP-DTBZ is a favorable PET ligand binding to VMAT2.     

Pharmacological studies of dopamine transporter imaging agent 125／131I－β－CIT

To prepare ^125/131I-β-CIT(2β-carbomethoxy-3β-(4-iodophenyl)tropane) as an imaging agent for dopamine transporter (DAT),the labeling method from tributylstannyl precursor with peracetic acid has been reported in this article.The radiochemical purity(RCP) of the labeled compound was over 95% determined by HPLC and TLC.The stability,partition coefficients were also determined.The pharmacological studies of the imaging agent were performed in rats,mice,rabbits and normal monkey.The ligand showed preferable uptake in rats,mice,rabbits and normal monkey.The ligand showed preferable uptake in brain (1.9%ID/organ in rats and 4.5%ID/organ in mice at 5min).The ratios of striatum/cerebellum,hippocampus/cerebellum and cortex/cerebellum were 29.8,3.97and 4.75 at 6h in rats,and 8.52,2.99 and 3.06 at 6h in mice,respectively.In monkey brain imaging the ratios of striatum/frontal cortex(ST/FC)and striatum/occipital cortex(ST/OC) were 5.14 and 5.97 at 4h.respectively,All of above showed the high affinity of the ligand to DAT,The compound was primarily metabolized in liver because the hepatic uptake was much higher than other organs(75.4%ID/organ at 18h).The half-life of blood elimination was 5min.The dose received by mice was 2500 times as high as that received by human in the test of undue toxicity,which evaluated the safety of the agent.All the results suggest that β-CIT can be used as a potential DAT imaging agent.     

The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

The preclinical pharmacological study of dopamine transporter imaging agent ^18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β-carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444, 0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum, striatum /frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

Synthesis and labelling of epidepride

S-(-)-N-[(1-ethyl-2-pyrrolidinyl)methyl]-5-iodo-2,3-dimethoxybenzamide(Proposed generic name,epidepride)is a very potent dopamine D2 antagonist.It was synthesized by five steps from 3-methoxysalicylic acid.[^131I]epidepride was obtained in 97.3% radiochemical yields from the corresponding 5-(tributylitin)derivative using hydrogen peroxide as the oxidant.The aryltin precursor was prepared from non-labelled epidepride by palladium-catalyzed stannylation using bis(tri-n-butyltin)in triethylamine.[^131I] epidepride was stable under 4℃,and partition coefficient was 72.3 at pH 7.40.The biodistribution study in rats exihibited high localization in the striatum of the rain with the striatum/cerebellum ratio reaching 237/1 at 320min postinjection.All these results suggest that[131I] epidepride may be used widely as a useful dopamine D2 receptor imaging agent for SPECT.     

Preparation and preliminary evaluation of [^55Co]（II）vancomycin

Co-55 （t1/2=17.53 h） was produced by 150 uA irradiation of a natural nickel target using 15 MeV protons. It was separated from the irradiated target material by two ion exchange chromatography steps with a radiochemical yield of 〉95% and was used for the preparation of [^55Co]vancomycin （[^55Co]VAN）. Optimization studies were performed using Co-57 due to its longer half-life. Cobalt-57 （t1/2=271.79 d） was produced by irradiation of a natural nickel target with 150 pA current of 22 MeV protons. The 57Co was separated from the irradiated target material using a no-carrier-added method with a radiochemical yield of 〉97%. Both products were controlled for radionuclide and chemical purity. The solutions of [^55Co]VAN were prepared （radiochemical yield〉80%） starting with 55Co acetate and vancomycin at room temperature after 30 min. A precise solid phrase extraction （SPE） method was developed using Si Sep-Pak in order to purify/reconstitute the final formulation for animal studies. [^55Co]VAN showed a radiochemical purity of more than 99%. The resultant specific activity was about 1.15 TBq/mmol. It is proved that the tracer is stable in the final product and in presence of human serum at 37℃ up to 24 h. Biodistribution study of [55Co]VAN in normal rats was undertaken for up to 72 h.     

RADIOBROMINE LABELLING OF 3,4-DIHYDROXY-PHENYL-L-ALANINE AND DISTRIBUTION STUDY IN MOUSE BRAIN

The synthesis of 3, 4-dihydroxy- 6- bromo- phenyl- L- alanine (6- Br- L- dopa ), preparation of 3,4-dihydroxy-6-[ Br] bromo-phenyl-L-alanine(6-77 Br-bromo-L-dopa) and its distribution study in mouse brain are described. The radiochemical yield and radiochemical purity of 6- Br-bromo-L-dopa were 8.5 % and 93 %, respectively. Its distribution in mouse brain after one hour injection indicates that it does pass blood brain barrier. The ratio of uptake in striatum to that in cerebellum was 2.45±0.12. The results appeared that 6- Br-bromo-L-dopa could be used as brain tracer for visualizing dopamine-containing brain structures by using single photon tomography.     

Synthesis, radiolabeling and animal studies of [^131I]MPPI： A 5-HT1A imaging agent

The synthesis and biological evaluation of serotonin （5-HT1A） imaging agent [^131I]- 4-iodo-N-{2-[4-（2-methoxyphenyl）-piperazin-l-yl]-ethyl}-N-pridin-2-yl-benzamide （[^131I]MPPI） are reported. The chemical structure of aimed compound and intermediates were confirmed by IR, ^1HNMR, and MS. Radiochemical purity was above 99% determined by TLC. Biodistribution of [^131I]MPPI in rats displayed high uptake in hippocampus and low uptake in cerebellum. The ratio of the uptake of [^131I]MPPI in hippocampus to that in cerebellum was 2.90 at 30 rain post injection. The radioactivity in thyroid was 0.069 and 0.128% ID/g organ at 5 min and 120 rain, respectively, and it was increased with time, which suggests that in vivo deiodination may be the major route of metabolism. Ex vivo autoradiography of brain section displayed significant decrease of radioactivity in hippocampus when pretreated with 8-OH-DPAT, a selective 5HT1A agonist, compared with control. These findings strongly suggested that ^131I-MPPI could be used as an in vivo marker for studies of pharmacology of the 5-HT1A receptor system in animals.     

Preliminary clinical application of dopamine transporter imaging with technetium—99m TRODAT—1 and SPECT on the early and differential diagnosis of Parkinson‘s Disease

The aim of the study was to demonstrate the degeneration of the dopaminergic nigrostriatal pathway in Parkinson‘s disease(PD)and Essential Tremor(ET) by using the cocaine derivative ^99m Tc-TRODAT-1 SPECT and correlate the findings to the clinical severities(Hoehn and Yahr scale,H/Y).28 patients with idiopathic Parkinson‘s disease,10 patients with Essential Tremor and 19 healthy volunteers were investigated.The acquisition were performed 3h postinjection of ^99mTc-TRODAT-1,ROIs were drawn over the images of striatum and cerebellum,and ratios of striatum to cerebellar(ST/CB) were calculated.Ratios differed significantly between PD and controls,but ratios didn‘t show significant difference between ET patients and controls.A significant correlation didn‘t exist between ratios and clincal severities.Hemiparkinson‘s patients revealed significantly diminished ^99mTc-TRODAT-1 binding not only clinically affected but unaffected side.Our findings indicated that ^99mTc-TRODAT-1 SPECT is not only a reliable method to discriminate between PD and controls but also a useful tool for differential diagnosis in clinically unclear cases such as ET resembling PD.     

Experimental study of triplex-forming oligonucleotide targeted to the initiator of S gene of HBV labeled with 125Ⅰ

This study is used to investigate the feasibility of employing the Iodogen method to label triplex-forming oligonucleotide (TFO) targeted to the initiator of the S gene of HBV with 125Ⅰ. A 17-mer oligonucleotides sequence was synthesized and grafted at the 5' terminal with a tyramine group. Radioiodination of the tyramine-TFO with 125Ⅰwas then performed using the Iodogen method. After TFO was labeled with 125Ⅰ using the Iodogen method, the labeling rate, the radiochemical purity, stability and bioactivity were determined, respectively. The results show that the radiolabeling rate and the radiochemical purity were 93% and 99%, respectively; and the radiochemical purity is more than 90% in vitro at -20℃ on the 5th day after labeling; and the rate of 125Ⅰ-tyramine-TFO binding to HepG2.2.15cells was (37.2±1.4) % and statistically different from the rate of HepG2 (p＜0.5). Hence, it is concluded that the labeling of oligonucleotides conjugated with tyramine using the Iodogen method is successful and is characterized with a high labeling rate, high stability, and a low loss of bioactivity of the labeled agent.     

腺苷A_(2A)受体显像剂~(11)C-KW6002的合成与初步生物学评价

腺苷A_(2A)受体与中枢神经退行性疾病密切相关,正电子核素标记的腺苷A_(2A)受体显像剂可用于帕金森病(PD)的诊断与疗效评价。本研究采用碳-11标记[(E)-1,3-二乙基-8-(3,4-二甲氧基苯乙烯)-7-甲基-3,7-双氢-1H-嘌呤-2,6-二酮](KW6002)制备~(11)C-KW6002,并进行正常鼠与PD模型鼠microPET显像。结果显示,以去甲基KW6002为标记前体,在NaOH条件下与三氟甲基磺酰基碳-11甲烷(~(11)CH_3-Trifcate)反应,标记率达56%(衰变校正,n=3)。经制备HPLC分离和固相萃取,产品放化纯度99.5%,比活度为1.5×10~(14)Bq/g。~(11)C-KW6002的microPET显像结果显示,正常大鼠双侧纹状体呈对称显像,PD模型鼠中毁损侧纹状体放射性较对侧明显增加,而同一模型的~(11)C-CFT显像为毁损侧纹状体放射性缺失。表明~(11)C-KW6002为具有临床应用的潜在腺苷A_(2A)受体显像剂。     

131I-epidepride的制备与SD大鼠体内分布特性研究

采用双氧水标记法和氯胺 -T法进行13 1I -epidepride标记 ,考察标记物的纯度及稳定性 ,并进行SD大鼠体内分布特性研究。实验结果表明 ,双氧水法和氯胺 -T法标记率分别为 97.4 %和 5 2 .9%。标记物的生理盐水溶液室温放置 4h ,放化纯大于 90 %。大鼠静脉注射13 1I -epide pride的生理盐水溶液后 ,纹状体与小脑比值在注射后 32 0min时高达 2 37:1。13 1I -epidepride进入血液后很快被组织摄取 ,其中以肺的早期摄取最高 (2 .11± 1.0 5 ) %ID·g- 1,各脏器的清除均较快 (T1/2 <4h) ,甲状腺的摄取率随时间的延长而增加。     

Comparative studies of D2 receptors and brain perfusion in hemi-parkinsonism rats

1 INTRODUCTIONParkinson's disease(PD) is characterized by selective loss of doptalnergic cellsin substantia nigra(SN) which project to striatum(ST), 14%~80% patients would accomphaed with dementia dUling their later stage of PD according to various statistic data, studies revealed deficit of regional cerebral blood flow (rCBF) and glucosemetabolism in frontal cortex etc. area in these patients[1]. The relationship betweencelltral dopalnine(DA) transactter system and brain perfusion i…     

多巴胺D2受体显像剂Epidepride的合成及其^131I标记

以3－甲氧基水杨酸为原料合成了Epidepride[S-(-)-N-[1-乙基－2－吡咯烷基]-5－碘－2,3－二甲氧基基甲酰胺]及其标记前体（S－（－）－5－（三正丁基锡）－N（1－乙基－2－吡咯烷基）甲基]2,3-二甲氧基苯甲酸酰胺）,并采用双氧水法对标记前体进行^131I标记,获得了^131I-epidepride,标记率和放化纯度均大于95％。132I-epidepride溶液体外稳定性好,4℃放置15d放化纯度仍大于90％。^131I-epidepride与D2受体亲和力高,大鼠脑内纹状体与小脑的摄取比在320min时高达237;在脑内纹状体的吸收可被Spiperone安全阻断。因此,^131I－epideride有望成为多巴胺D2受体SPECT显像剂。     

Synthesis, radiolabeling and animal studies of [~(131)I]MPPI: A 5-HTB_(1A) imaging agent

1 Introduction In the last two decades, considerable progress has been made in the understanding of the central nervous system (CNS) serotonin system. It is an important neurotransmission network that regulates various physiological functions and behavior, including anxi-ety and affective states.P[1-3]P The family of receptors activated by the neurotransmitter serotonin has been divided into at least seven classes (5-HTB1-7B), some of them further subdivided into different subtypesP[4, 5]P…