Design and Synthesis of Clinical Candidate PF-06852231 (CVL-231): A Brain Penetrant, Selective, Positive Allosteric Modulator of the M 4 Muscarinic Acetylcholine Receptor.

Selective activation of the M 4 muscarinic acetylcholine receptor subtype offers a novel strategy for the treatment of psychosis in multiple neurological disorders. Although the development of traditional muscarinic activators has been stymied due to pan-receptor activation, muscarinic receptor subtype selectivity can be achieved through the utilization of a subtype of a unique allosteric site. A major challenge in capitalizing on this allosteric site to date has been achieving a balance of suitable potency and brain penetration. Herein, we describe the design of a brain penetrant series of M 4 selective positive allosteric modulators (PAMs), ultimately culminating in the identification of 21 ( PF-06852231, now CVL-231/emraclidine), which is under active clinical development as a novel mechanism and approach for the treatment of schizophrenia.