Takeda Pharmaceutical Company Limited, 26-1 Muraoka-Higashi, 2-Chome, Fujisawa, Kanagawa, 251-8555, Japan.
Invicro, LLC, New Haven, CT, USA.
Eur J Nucl Med Mol Imaging. 2022 Mar;49(4):1148-1156. doi: 10.1007/s00259-021-05565-z. Epub 2021 Oct 15.
Cholesterol 24-hydroxylase (CH24H) is a brain-specific enzyme that plays a major role in brain cholesterol homeostasis by converting cholesterol into 24S-hydroxycholesterol. The selective CH24H inhibitor soticlestat (TAK-935) is being pursued as a drug for treatment of seizures in developmental and epileptic encephalopathies. Herein, we describe the successful discovery and the preclinical validation of the novel radiolabeled CH24H ligand (3-[F]fluoroazetidin-1-yl){1-[4-(4-fluorophenyl)pyrimidin-5-yl]piperidin-4-yl}methanone ([F]T-008) and its tritiated analog, [H]T-008.
In vitro autoradiography (ARG) studies in the CH24H wild-type (WT) and knockout (KO) mouse brain sections were conducted using [H]T-008. PET imaging was conducted in two adult rhesus macaques using [F]T-008. Each macaque received two test-retest baseline scans and a series of two blocking doses of soticlestat administered prior to [F]T-008 to determine the CH24H enzyme occupancy. PET data were analyzed with Logan graphical analysis using plasma input. A Lassen plot was applied to estimate CH24H enzyme occupancy by soticlestat.
In ARG studies, binding of [H]T-008 was specific to CH24H in the mouse brain sections, which was not observed in CH24H KO or in wild-type mice after pretreatment with soticlestat. In rhesus PET studies, the rank order of [F]T-008 uptake was striatum > cortical regions > cerebellum, which was consistent with CH24H distribution in the brain. Pre-blocking with soticlestat reduced the maximum uptake and increased the washout in all brain regions in a dose-dependent manner. Calculated global occupancy values for soticlestat at a dose of 0.89 mg/kg were 97-98%, indicating maximum occupancy.
The preclinical in vitro and in vivo evaluation of labeled T-008 demonstrates that [F]T-008 is suitable for imaging CH24H in the brain and warrants further studies in humans.
胆固醇 24-羟化酶（CH24H）是一种脑特异性酶，通过将胆固醇转化为 24S-羟胆固醇，在脑胆固醇稳态中发挥重要作用。选择性 CH24H 抑制剂索替司他（TAK-935）被作为治疗发育性和癫痫性脑病发作的药物进行研究。本文描述了新型放射性标记 CH24H 配体（3-[F]氟氮杂环丁烷-1-基）{1-[4-（4-氟苯基）嘧啶-5-基]哌啶-4-基}甲酮（[F]T-008）及其氚代类似物[H]T-008 的成功发现和临床前验证。
使用[H]T-008 在 CH24H 野生型（WT）和敲除（KO）小鼠脑切片中进行体外放射性自显影（ARG）研究。使用[F]T-008 在两只成年恒河猴中进行 PET 成像。每只猴子接受两次测试-复测基线扫描和一系列两次索替司他阻断剂量，以确定 CH24H 酶占有率。使用 Logan 图形分析方法和血浆输入对 PET 数据进行分析。应用 Lassen 图估计索替司他对 CH24H 酶占有率。
在 ARG 研究中，[H]T-008 与小鼠脑切片中的 CH24H 特异性结合，而在 CH24H KO 或用索替司他预处理后的野生型小鼠中未观察到这种结合。在恒河猴 PET 研究中，[F]T-008 的摄取量顺序为纹状体 > 皮质区 > 小脑，与脑内 CH24H 分布一致。用索替司他预先阻断以剂量依赖性方式降低了所有脑区的最大摄取量和增加了洗脱量。在 0.89 mg/kg 剂量下，索替司他的全球占有率值计算为 97-98%，表明达到最大占有率。
标记 T-008 的临床前体内外评价表明，[F]T-008 适合于脑内 CH24H 成像，值得在人类中进一步研究。
