In Vivo Quantification of Calcitonin Gene-Related Peptide Receptor Occupancy by Telcagepant in Rhesus Monkey and Human Brain Using the Positron Emission Tomography Tracer [<sup>11</sup>C]MK-4232
作者:Eric D. Hostetler、Aniket D. Joshi、Sandra Sanabria-Bohórquez、Hong Fan、Zhizhen Zeng、Mona Purcell、Liza Gantert、Kerry Riffel、Mangay Williams、Stacey O’Malley、Patricia Miller、Harold G. Selnick、Steven N. Gallicchio、Ian M. Bell、Christopher A. Salvatore、Stefanie A. Kane、Chi-Chung Li、Richard J. Hargreaves、Tjibbe de Groot、Guy Bormans、Anne Van Hecken、Inge Derdelinckx、Jan de Hoon、Tom Reynders、Ruben Declercq、Inge De Lepeleire、W. P. Kennedy、Rebecca Blanchard、Eugene E. Marcantonio、Cyrille Sur、Jacquelynn J. Cook、Koen Van Laere、Jeffrey L. Evelhoch
DOI:10.1124/jpet.113.206458
日期:2013.11
Calcitonin gene-related peptide (CGRP) is a potent neuropeptide whose agonist interaction with the CGRP receptor (CGRP-R) in the periphery promotes vasodilation, neurogenic inflammation and trigeminovascular sensory activation. This process is implicated in the cause of migraine headaches, and CGRP-R antagonists in clinical development have proven effective in treating migraine-related pain in humans. CGRP-R is expressed on blood vessel smooth muscle and sensory trigeminal neurons and fibers in the periphery as well as in the central nervous system. However, it is not clear what role the inhibition of central CGRP-R plays in migraine pain relief. To this end, the CGRP-R positron emission tomography (PET) tracer [11C]MK-4232 (2-[(8 R )-8-(3,5-difluorophenyl)-6,8-[6-11C]dimethyl-10-oxo-6,9-diazaspiro[4.5]decan-9-yl]- N -[(2 R )-2′-oxospiro[1,3-dihydroindene-2,3′-1 H -pyrrolo[2,3- b ]pyridine]-5-yl]acetamide) was discovered and developed for use in clinical PET studies. In rhesus monkeys and humans, [11C]MK-4232 displayed rapid brain uptake and a regional brain distribution consistent with the known distribution of CGRP-R. Monkey PET studies with [11C]MK-4232 after intravenous dosing with CGRP-R antagonists validated the ability of [11C]MK-4232 to detect changes in CGRP-R occupancy in proportion to drug plasma concentration. Application of [11C]MK-4232 in human PET studies revealed that telcagepant achieved only low receptor occupancy at an efficacious dose (140 mg PO). Therefore, it is unlikely that antagonism of central CGRP-R is required for migraine efficacy. However, it is not known whether high central CGRP-R antagonism may provide additional therapeutic benefit.
降钙素基因相关肽(CGRP)是一种强效神经肽,其激动剂与外周的 CGRP 受体(CGRP-R)相互作用,可促进血管扩张、神经源性炎症和三叉神经血管感觉激活。这一过程与偏头痛的病因有关,临床开发中的 CGRP-R 拮抗剂已被证明能有效治疗人类偏头痛相关的疼痛。CGRP-R 在血管平滑肌、三叉神经感觉神经元和纤维的外周以及中枢神经系统中均有表达。然而,目前尚不清楚抑制中枢 CGRP-R 在缓解偏头痛疼痛方面发挥了什么作用。为此,CGRP-R 正电子发射断层扫描(PET)示踪剂 [11C]MK-4232 (2-[(8 R )-8-(3,5-difluorophenyl)-6,8-[6-11C]dimethyl-10-oxo-6,9-diazaspiro[4.5]癸烷-9-基]-N-[(2 R )-2′-氧代螺[1,3-二氢茚-2,3′-1 H -吡咯并[2,3- b ]吡啶]-5-基]乙酰胺)被发现并开发用于临床 PET 研究。在恒河猴和人体内,[11C]MK-4232 显示出快速的脑摄取,其脑区域分布与已知的 CGRP-R 分布一致。在静脉注射 CGRP-R 拮抗剂后,用 [11C]MK-4232 对猴子进行 PET 研究,验证了 [11C]MK-4232 检测 CGRP-R 占有率与药物血浆浓度成比例变化的能力。在人体 PET 研究中应用[11C]MK-4232 发现,在有效剂量(140 毫克 PO)下,telcagepant 只能达到较低的受体占用率。因此,偏头痛的疗效不太可能需要拮抗中枢 CGRP-R。不过,中枢 CGRP-R 的高度拮抗作用是否会带来额外的治疗效果,目前还不得而知。