MK-6884, a positive allosteric modulator (PAM) of M4 muscarinic receptors, exhibits a high affinity (Ki = 0.19 nM). It is a valuable compound for the investigation of neurodegenerative diseases. Additionally, MK-6884 can be efficiently radiolabeled with carbon-11, enabling its use as a PET imaging agent.

MK-6884 (compound 13; 0-22 μM) is a PAM of ACh function in a cell-based Ca 2+ mobilization assay, with an EC 50 of 27 nM[1].

[ 11 C]MK-6884 (compound 13) shows non-displaceable binding potential (BP ND ) of 0.83 in rhesus monkeys[1]. [ 11 C]MK-6884 (approximately 185 MBq, <2 μg; single intravenous) distributes on the known presence of M4 receptors in the rhesus monkeys brain[1]. [ 11 C]MK-688 can penetrate the blood-brain barrier in monkeys[1].