PET ligand discovery for arginine vasopressin

项目摘要。V1a特异性的精氨酸加压素受体最近成为中枢神经系统研究的焦点 当受体基因与自闭症谱系障碍(ASD)之间的关联被确认时。失调症 V1a活性被认为是ASD病理生理学的基本机制。最新研究 揭示V1a拮抗剂可以调节AVP激素的作用，从而解决潜在的根本原因 ASD的发展。PET能够量化体内的生化过程，而合适的V1APET配体将 大大提高了我们对不同病理生理条件下V1a介导的AVP信号的理解， 否则无法通过体外(破坏性)分析，特别是在高等物种中。V1a在生活中的量化 脑部正电子发射计算机断层扫描将提供新的V1a分布、表达和靶向参与的评估。 靶向神经疗法。到目前为止，还没有成功的例子来显示V1a特定的AVP 供人类使用，代表着我们在体内研究V1a靶点的能力的一个重大缺陷。因此，我们 建议开发一种新型的PET配体来填补这一空白，作为第一个翻译成像工具。 PI最近在2021年的MGH上开发了一种新的V1a特异的AVP配体[11C]PF-184563。虽然这件事 化合物显示出高效力和良好的选择性，但由于脑渗透率较低，因此不太可能被追捧。在我们的 第二代，我们鉴定了一种铅分子，V1a-214，它显示出显著改善的结合亲和力和 在所有其他主要CNS目标中，具有极好的目标选择性。合成了V1a-214的~(11)C同位素体， 初步的PET成像研究证实，我们已经克服了V1a特异性PET配体的两个主要障碍 通过实现：1)高脑摄取(&gt；1 SUV)和2)高靶点特异性被人类V1a细胞证实的发育 体内的线条和阻断研究，异源摄取与中枢神经系统中的V1a区域一致。尽管V1a- 由于物种差异，214是一种很有前途的前导分子，可用于开发V1a靶向的新的PET配体。 进一步优化翻译跨物种(幼稚/人源化的V1a小鼠和非人灵长类)成像 为了药物发现和临床，人们试图在活脑中实现最佳的AVP(V1a亚单位)的量化 ASD患者的生物标记物。 在V1A-214作为药物化学优化的有效引线的基础上，作为具体目标，我们 将设计和准备一个V1a特异性拮抗剂的重点文库，可以用11C或18F标记，以及 评估他们在幼稚和人源化的细胞实验中量化V1a特异性AVP活性和变化的能力 V1a小鼠和非人灵长类动物，以及死后NHP/人类的放射自显影和生物学验证 脑组织。这项工作的影响不仅是成功地开发出第一个高亲和力和选择性的V1a特异性 PET配体用于ASD相关生物学过程的研究，也最终通过PET成像验证在高等 将该配体作为潜在的临床生物标志物并用于监测新的靶向反应 治疗神经发育疾病和神经精神障碍，包括自闭症。

Project Summary. The V1A-specific arginine vasopressin receptor has recently become the focus of CNS research when an association between the receptor gene and autism spectrum disorder (ASD) is identified. Dysregulation of V1A activity has been suggested as a fundamental mechanism underlying ASD pathophysiology. Recent studies revealed that V1A antagonists can regulate the effect of the AVP hormone, thereby tackling a potential root cause of ASD development. PET is capable of quantifying biochemical processes in vivo, and a suitable V1A PET ligand would substantially improve our understanding of V1A-mediated AVP signaling under different pathophysiological conditions, otherwise inaccessible by ex vivo (destructive) analysis, particularly in higher species. Quantification of V1A in living brain by PET would provide the assessment of distribution and expression and target engagement of new V1A- targeted neurotherapeutics. To date, no successful examples have been demonstrated to image V1A-specific AVP for human use, representing a significant deficiency of our ability to study this target in vivo for V1A. Therefore, we propose to develop a novel PET ligand that can fill this void, as the first translational imaging tool. The PI has recently developed a novel V1A-specific AVP ligand [11C]PF-184563 at MGH in 2021. While this compound showed high potency and excellent selectivity, it is not likely pursued due to low brain penetration. In our 2nd generation, we identified a lead molecule, V1A-214, which showed substantially-improved binding affinity and excellent target selectivity among all other major CNS targets. An 11C-isotopologue of V1A-214 was synthesized and preliminary PET imaging studies confirmed that we have overcome two major obstacles for V1A-specific PET ligand development by achieving: 1) high brain uptake (>1 SUV) and 2) high target specificity validated by human V1A cell lines and blocking studies in vivo, and heterogenous uptake consistent with V1A regions in the CNS. Though V1A- 214 is a promising lead molecule for the development of new V1A-targeted PET ligands, due to species difference, further optimization for translational cross-species (naïve/humanized V1A mice and nonhuman primates) imaging studies are sought to achieve optimal AVP (V1A subunit) quantification in the living brain for drug discovery and clinical biomarker for ASD patients. On the basis that V1A-214 serves a validated lead for medicinal chemistry optimization, as specific objectives, we will design and prepare a focused library of V1A-specific antagonists amenable for labeling with 11C or 18F, and evaluate their ability to quantify V1A-specific AVP activity and changes in cellular experiments, naïve and humanized V1A mice and nonhuman primates, as well as autoradiography and biological validation in postmortem NHP/human brain tissues. The impact of this work is not only to develop the first successful high-affinity and selective V1A-specific PET ligand for the study of ASD-related biological processes, but also ultimately, via PET imaging validation in higher species, to advance this ligand as a potential clinical biomarker and for monitoring target response of novel therapeutics for neurodevelopmental diseases and neuropsychiatric disorders, including ASD.