[Image: see text] The discovery of PIPE-359, a brain-penetrant and selective antagonist of the muscarinic acetylcholine receptor subtype 1 is described. Starting from a literature-reported M(1) antagonist, linker replacement and structure–activity relationship investigations of the eastern 1-(pyridinyl)piperazine led to the identification of a novel, potent, and selective antagonist with good MDCKII-MDR1 permeability. Continued semi-iterative positional scanning facilitated improvements in the metabolic and hERG profiles, which ultimately delivered PIPE-359. This advanced drug candidate exhibited robust efficacy in mouse myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalitis (EAE), a preclinical model for multiple sclerosis.