Abstract：
BACKGROUND: In vivo positron emission tomography (PET) imaging of the serotonin transporter (SERT) is a valuable tool in drug development and in monitoring brain diseases with altered serotonergic function. We have developed a two-step labeling reaction for the preparation of the high serotonin affinity ligand [(18)F]FPBM ([(18)F]2-(2\'-((dimethylamino)methyl)-4\'-(3-fluoropropoxy)phenylthio)benzenamine, 1).
METHODS: To improve and automate the radiolabeling of [(18)F]FPBM, 1, an intermediate, [(18)F]3-fluoropropyltosylate, [(18)F]4, was prepared first, and then it was reacted with the phenol precursor (4-(2-aminophenylthio)-3-((dimethylamino)methyl)phenol, 3) to afford [(18)F]FPBM, 1. To optimize the labeling, this O-alkylation reaction was evaluated under different temperatures, using different bases and varying amounts of precursor 3. The desired product was obtained after a solid phase extraction (SPE) purification.
RESULTS: This two-step radiolabeling reaction successfully produced the desired [(18)F]FPBM, 1, with an excellent radiochemical purity (>95%, n = 8). Radiochemical yields were between 31% and 39% (decay corrected, total time of labeling: 70 min, n = 8). The SPE purification cannot completely remove pseudo-carriers in the final dose of [(18)F]FPBM, 1. The concentrations of major pseudo-carriers were measured by UV-HPLC (476-676, 68-95 and 50-71 μg for precursor 3, O-hydroxypropyl and O-allyloxy derivatives, 5 and 6, respectively). To investigate the potential inhibition of SERT binding of these pseudo-carriers, we performed in vitro competition experiments evaluated by autoradiography. Known amounts of \'standard\' FPBM, 1, of the pseudo-carriers, 5 and 6, were added to the HPLC-purified [(18)F]1 dose. The inhibition of \'standard\' FPBM, 1, binding to the SERT binding sites, using monkey brain sections, were measured (EC50=13, 46, 7.1 and 8.3 nM, respectively for 1, precursor 3, O-hydroxypropyl and O-allyloxy derivative of 3).
CONCLUSIONS: An improved radiolabeling method by a SPE purification for preparation of [(18)F]FPBM, 1, was developed. The results suggest that it is feasible to use this labeling method to prepare [(18)F]FPBM, 1, without affecting in vivo SERT binding.
METHODS: To improve and automate the radiolabeling of [(18)F]FPBM, 1, an intermediate, [(18)F]3-fluoropropyltosylate, [(18)F]4, was prepared first, and then it was reacted with the phenol precursor (4-(2-aminophenylthio)-3-((dimethylamino)methyl)phenol, 3) to afford [(18)F]FPBM, 1. To optimize the labeling, this O-alkylation reaction was evaluated under different temperatures, using different bases and varying amounts of precursor 3. The desired product was obtained after a solid phase extraction (SPE) purification.
RESULTS: This two-step radiolabeling reaction successfully produced the desired [(18)F]FPBM, 1, with an excellent radiochemical purity (>95%, n = 8). Radiochemical yields were between 31% and 39% (decay corrected, total time of labeling: 70 min, n = 8). The SPE purification cannot completely remove pseudo-carriers in the final dose of [(18)F]FPBM, 1. The concentrations of major pseudo-carriers were measured by UV-HPLC (476-676, 68-95 and 50-71 μg for precursor 3, O-hydroxypropyl and O-allyloxy derivatives, 5 and 6, respectively). To investigate the potential inhibition of SERT binding of these pseudo-carriers, we performed in vitro competition experiments evaluated by autoradiography. Known amounts of \'standard\' FPBM, 1, of the pseudo-carriers, 5 and 6, were added to the HPLC-purified [(18)F]1 dose. The inhibition of \'standard\' FPBM, 1, binding to the SERT binding sites, using monkey brain sections, were measured (EC50=13, 46, 7.1 and 8.3 nM, respectively for 1, precursor 3, O-hydroxypropyl and O-allyloxy derivative of 3).
CONCLUSIONS: An improved radiolabeling method by a SPE purification for preparation of [(18)F]FPBM, 1, was developed. The results suggest that it is feasible to use this labeling method to prepare [(18)F]FPBM, 1, without affecting in vivo SERT binding.
摘要：
背景：血清素转运蛋白（SERT）的体内正电子发射断层扫描（PET）成像是药物开发和监测血清素能功能改变的脑部疾病的有价值的工具。我们已经开发了两步标记反应，用于制备高5-羟色胺亲和配体[（18）F]FPBM（[（18）F]2-（2'-（（二甲基氨基）甲基）-4'-（3-氟丙氧基）苯硫基）苯胺，1).
方法：为了改进和自动化[（18）F]FPBM的放射性标记，1、中间、[(18)F]3-氟丙基甲苯磺酸酯，[(18)F]4，首先准备好了，然后与苯酚前体(4-(2-氨基苯硫基)-3-((二甲基氨基)甲基)苯酚反应，3)提供[(18)F]FPBM，1.要优化标签，该O-烷基化反应在不同温度下进行评价，使用不同的碱和不同量的前体3.在固相萃取(SPE)纯化后获得所需产物。
结果：这种两步放射性标记反应成功地产生了所需的[（18）F]FPBM，1，具有优异的放射化学纯度（>95％，n=8)。放射化学产率在31%和39%之间(衰变校正，标签的总时间：70分钟，n=8)。SPE纯化不能完全去除[(18)F]FPBM最终剂量中的假载体，1.通过UV-HPLC测量主要假载体的浓度（前体3，O-羟丙基和O-烯丙氧基衍生物的476-676、68-95和50-71μg，分别为5和6）。为了研究这些假载体的SERT结合的潜在抑制作用，我们进行了体外竞争实验，通过放射自显影评估。已知数量的\'标准\'FPBM，1，在伪载波中，将5和6加入到HPLC纯化的[(18)F]1剂量中。“标准”FPBM的抑制，1，与SERT结合位点结合，用猴子的大脑切片，测量(EC50=13、46、7.1和8.3nM，分别为1，前体3，O-羟丙基和O-烯丙氧基衍生物3）。
结论：通过SPE纯化制备[（18）F]FPBM的改进的放射性标记方法，1、开发。结果表明，使用该标记方法制备[（18）F]FPBM是可行的，1，不影响体内SERT结合。
方法：为了改进和自动化[（18）F]FPBM的放射性标记，1、中间、[(18)F]3-氟丙基甲苯磺酸酯，[(18)F]4，首先准备好了，然后与苯酚前体(4-(2-氨基苯硫基)-3-((二甲基氨基)甲基)苯酚反应，3)提供[(18)F]FPBM，1.要优化标签，该O-烷基化反应在不同温度下进行评价，使用不同的碱和不同量的前体3.在固相萃取(SPE)纯化后获得所需产物。
结果：这种两步放射性标记反应成功地产生了所需的[（18）F]FPBM，1，具有优异的放射化学纯度（>95％，n=8)。放射化学产率在31%和39%之间(衰变校正，标签的总时间：70分钟，n=8)。SPE纯化不能完全去除[(18)F]FPBM最终剂量中的假载体，1.通过UV-HPLC测量主要假载体的浓度（前体3，O-羟丙基和O-烯丙氧基衍生物的476-676、68-95和50-71μg，分别为5和6）。为了研究这些假载体的SERT结合的潜在抑制作用，我们进行了体外竞争实验，通过放射自显影评估。已知数量的\'标准\'FPBM，1，在伪载波中，将5和6加入到HPLC纯化的[(18)F]1剂量中。“标准”FPBM的抑制，1，与SERT结合位点结合，用猴子的大脑切片，测量(EC50=13、46、7.1和8.3nM，分别为1，前体3，O-羟丙基和O-烯丙氧基衍生物3）。
结论：通过SPE纯化制备[（18）F]FPBM的改进的放射性标记方法，1、开发。结果表明，使用该标记方法制备[（18）F]FPBM是可行的，1，不影响体内SERT结合。
