1. Academic Validation
  2. Radiosynthesis and Preclinical Evaluation of a Carbon-11 Labeled Phosphodiesterase 7 Inhibitor for PET Neuroimaging

Radiosynthesis and Preclinical Evaluation of a Carbon-11 Labeled Phosphodiesterase 7 Inhibitor for PET Neuroimaging

  • ACS Med Chem Lett. 2025 Aug 18;16(9):1835-1843. doi: 10.1021/acsmedchemlett.5c00385.
Zhiwei Xiao 1 Jiyun Sun 1 Masayuki Fujinaga 2 Huiyi Wei 3 Chunyu Zhao 1 Achi Haider 1 Richard Van 4 Shi Kuang 5 Tomoteru Yamasaki 2 Yiding Zhang 2 Jian Rong 1 Kuan Hu 2 Jiahui Chen 1 Erick Calderon Leon 4 Wakana Mori 2 Lin Xie 2 Junjie Wei 3 Yi Xu 6 Yihan Shao 4 Han-Ting Zhang 7 Ying Xu 8 Chongzhao Ran 5 Kc Kent Lloyd 9 Lu Wang 3 Ming-Rong Zhang 2 Steven H Liang 1
Affiliations

Affiliations

  • 1 Department of Radiology, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital and Harvard Medical School, 55 Fruit Street, Boston, Massachusetts 02114, United States.
  • 2 Department of Advanced Nuclear Medicine Sciences, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba 263-8555, Japan.
  • 3 Center of Cyclotron and PET Radiopharmaceuticals, Department of Nuclear Medicine, and PET/CT-MRI Center, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China.
  • 4 Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, United States.
  • 5 Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, United States.
  • 6 Department of Cardiology, The First Affiliated Hospital of Jinan University, Guangzhou 510630, China.
  • 7 Departments of Neuroscience, Behavioral Medicine & Psychiatry, Physiology, and Pharmacology, the Rockefeller Neuroscience Institute, West Virginia University Health Sciences Center, Morgantown, West Virginia 26506, United States.
  • 8 Department of Anesthesiology, Rutgers, The State University of New Jersey, Newark, New Jersey 07103, United States.
  • 9 Department of Surgery, School of Medicine, and Mouse Biology Program, University of California, Davis, 2795 Second Street, Suite 400, Davis, California 95618, United States.
Abstract

Dysfunction of cyclic nucleotide phosphodiesterase 7 (PDE7) has been associated with excess intracellular cAMP concentrations, fueling pathogenic processes that are implicated in neurodegenerative disorders. This study aimed to develop a suitable positron emission tomography (PET) probe that allows noninvasive mapping of PDE7 in the mammalian brain. Based on a spiro cyclohexane-1,4'-quinazolinone scaffold with known inhibitory properties toward PDE7, we designed and synthesized a carbon-11 labeling tolerant methoxy analog. The resulting PET probe, code named [11C]-P7-2104 (27), was synthesized in high molar activities (170-220 GBq/μmol) with decay-corrected radiochemical yields of 34 ± 7%. In vitro cell uptake of [11C]27 was 6-7-fold higher in PDE7 overexpressing cells compared to the controls, whereas an in vitro specificity of up to 90% was measured. Ex vivo metabolite studies revealed a high fraction of intact parent in the rat brain (98% at 5 min and 75% at 30 min postinjection). Considerable brain penetration was further corroborated by ex vivo biodistribution and PET imaging studies, the latter showing heterogenic brain uptake. While marginal blockade was observed by PET studies in rodents, a moderate, but dose-dependent, blockade was observed in the non-human primate brain following pretreatment with nonradioactive 27. Accordingly, [11C]27 will serve as a valuable lead compound for the development of a new arsenal of PDE7-targeted probes.

Keywords

Inhibitor; Phosphodiesterase 7; Positron emission tomography; Quinazolinone scaffold; Radioligand.

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