Discovery and optimization of a novel series of highly CNS penetrant M4 PAMs based on a 5,6-dimethyl-4-(piperidin-1-yl)thieno[2,3-d]pyrimidine core.

Wood MR, Noetzel MJ, Engers JL, Bollinger KA, Melancon BJ, Tarr JC, Han C, West M, Gregro AR, Lamsal A, Chang S, Ajmera S, Smith E, Chase P, Hodder PS, Bubser M, Jones CK, Hopkins CR, Emmitte KA, Niswender CM, Wood MW, Duggan ME, Conn PJ, Bridges TM, Lindsley CW
Bioorg Med Chem Lett. 2016 26 (13): 3029-3033

PMID: 27185330 · PMCID: PMC4955361 · DOI:10.1016/j.bmcl.2016.05.010

This Letter describes the chemical optimization of a novel series of M4 positive allosteric modulators (PAMs) based on a 5,6-dimethyl-4-(piperidin-1-yl)thieno[2,3-d]pyrimidine core, identified from an MLPCN functional high-throughput screen. The HTS hit was potent and selective, but not CNS penetrant. Potency was maintained, while CNS penetration was improved (rat brain:plasma Kp=0.74), within the original core after several rounds of optimization; however, the thieno[2,3-d]pyrimidine core was subject to extensive oxidative metabolism. Ultimately, we identified a 6-fluoroquinazoline core replacement that afforded good M4 PAM potency, muscarinic receptor subtype selectivity and CNS penetration (rat brain:plasma Kp>10). Moreover, this campaign provided fundamentally distinct M4 PAM chemotypes, greatly expanding the available structural diversity for this exciting CNS target.

Copyright © 2016 Elsevier Ltd. All rights reserved.

MeSH Terms (12)

Allosteric Regulation Animals Brain Humans Microsomes, Liver Piperidines Pyrimidines Quinazolines Rats Receptor, Muscarinic M4 Structure-Activity Relationship Thiophenes

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