The PET tracer [11C]MK-6884 quantifies M4 muscarinic receptor in rhesus monkeys and patients with Alzheimer's disease

Wenping Li, Yuchuan Wang, Talakad G. Lohith, Zhizhen Zeng, Ling Tong, Robert Mazzola, Kerry Riffel, Patricia Miller, Mona Purcell, Marie Holahan, Hyking Haley, Liza Gantert, David Hesk, Sumei Ren, John Morrow, Jason Uslaner, Arie Struyk, Jenny Miu Chun Wai, Michael T. Rudd, David M. TellersThomas McAvoy, Guy Bormans, Michel Koole, Koen Van Laere, Kim Serdons, Jan De Hoon, Ruben Declercq, Inge De Lepeleire, Maria B. Pascual, Paolo Zanotti-Fregonara, Meixiang Yu, Victoria Arbones, Joseph C. Masdeu, Amy Cheng, Azher Hussain, Tjerk Bueters, Matt S. Anderson, Eric D. Hostetler, Anthony S. Basile

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Positron emission tomography (PET) ligands play an important role in the development of therapeutics by serving as target engagement or pharmacodynamic biomarkers. Here, we describe the discovery and translation of the PET tracer [11C]MK-6884 from rhesus monkeys to patients with Alzheimer's disease (AD). [3H]MK-6884/[11C]MK-6884 binds with high binding affinity and good selectivity to an allosteric site on M4 muscarinic cholinergic receptors (M4Rs) in vitro and shows a regional distribution in the brain consistent with M4R localization in vivo. The tracer demonstrates target engagement of positive allosteric modulators of the M4R (M4 PAMs) through competitive binding interactions. [11C]MK-6884 binding is enhanced in vitro by the orthosteric M4R agonist carbachol and indirectly in vivo by the acetylcholinesterase inhibitor donepezil in rhesus monkeys and healthy volunteers, consistent with its pharmacology as a highly cooperative M4 PAM. PET imaging of [11C]MK-6884 in patients with AD identified substantial regional differences quantified as nondisplaceable binding potential (BPND) of [11C]MK-6884. These results suggest that [11C]MK-6884 is a useful target engagement biomarker for M4 PAMs but may also act as a sensitive probe of neuropathological changes in the brains of patients with AD.

Original languageEnglish (US)
Article numbereabg3684
Pages (from-to)eabg3684
JournalScience translational medicine
Issue number627
StatePublished - Jan 12 2022


  • Acetylcholinesterase
  • Alzheimer Disease/diagnostic imaging
  • Animals
  • Humans
  • Macaca mulatta
  • Positron-Emission Tomography/methods
  • Receptors, Muscarinic

ASJC Scopus subject areas

  • Medicine(all)


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