Rapid identification of a novel phosphodiesterase 7B tracer for receptor occupancy studies using LC-MS/MS
Rapid identification of a novel phosphodiesterase 7B tracer for receptor occupancy studies using LC-MS/MS
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DOI：
10.1016/j.neuint.2020.104735
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发表时间：
2020-07-01
影响因子：
4.2
通讯作者：
Tabatabaei, Ali
中科院分区：
文献类型：
--
作者：
Chen, Jie;Gu, Guibao;Tabatabaei, Ali
磷酸二酯酶7B （PDE7B）抑制已被认为是治疗几种神经系统疾病的治疗靶点。目前，没有放射性标记示踪剂可用于确定该靶标的受体占用（RO）。开发这样的示踪剂可以极大地促进鉴定可行的PDE7B抑制剂。在本研究中，采用液相色谱串联质谱（LC-MS/MS）方法评估静脉微量给药后未标记示踪剂候选物的脑分布。这种新方法加速了对PDE7B潜在的新型RO示踪剂的鉴定。所鉴定的化合物30在未标记化合物的大鼠中表现出合理的靶组织特异性（纹状体/小脑比值为2.2）和适当的摄取（注射剂量/g脑组织的0.25%）。化合物30随后用氚（H-3）标记。对H-3-Compound 30的体外表征表明，该化合物具有亚纳摩尔K-d （0.8 nM）和58 fmol/mg的B-ma(x)的高靶亲和力。静脉微给药H-3-Compound 30在大鼠纹状体中表现出优先结合，与PDE7B mRNA的分布一致。利用大鼠脑匀浆与其他结构不同的PDE7B靶标特异性抑制剂进行的体外置换研究表明，h -3-化合物30是一种理想的K-i分析示踪剂。这是关于PDE7B临床前示踪剂的第一篇报道。随着进一步的表征，化合物30可能最终显示出作为PDE7B PET配体进一步开发用于临床研究所需的适当性质。
Phosphodiesterase 7B (PDE7B) inhibition has been considered as a therapeutic target for the treatment of several neurological disorders. Currently, there are no radio-labeled tracers available to determine receptor occupancy (RO) of this target. Developing such a tracer could greatly facilitate the identification of viable PDE7B inhibitors. In the current study, a liquid chromatography tandem mass spectrometry (LC-MS/MS) method was utilized to evaluate the brain distribution of unlabeled tracer candidates following intravenous micro-dosing. This novel approach resulted in an accelerated identification of a potential novel RO tracer for PDE7B. The identified molecule, Compound 30, showed reasonable target-tissue specificity (striatum/cerebellum ratio of 2.2) and suitable uptake (0.25% of the injected dose/g brain tissue) as demonstrated in rats dosed with the unlabeled compound. Compound 30 was subsequently labeled with tritium (H-3). In vitro characterization of H-3-Compound 30 demonstrated that this compound possessed a high target affinity with a subnanomolar K-d (0.8 nM) and a B-ma(x) of 58 fmol/mg of protein using rat brain homogenate. Intravenous microdosing of H-3-Compound 30 showed preferential binding in the rat striatum, consistent with the mRNA distribution of PDE7B. In vitro displacement study with other structurally distinct PDE7B target-specific inhibitors using rat brain homogenate indicated that H-3-Compound 30 is an ideal tracer for K-i analysis. This is the first report of a preclinical tracer for PDE7B. With further characterization, Compound 30 may ultimately show the appropriate properties required to be further developed as a PDE7B PET ligand for clinical studies.