PCS1055 dihydrochloride is a potent, selective and competitive muscarinic M4 receptor antagonist with an IC 50 of 18.1 nM and a K d of 5.72 nM. PCS1055 dihydrochloride inhibits radioligand [ 3 H]-NMS binding to the M4 receptor with a K i of 6.5 nM. PCS1055 dihydrochloride exhibits >100-fold selectivity over M1-, M3-, and M5-receptors and 30-fold selectivity at the M2 receptor. PCS1055 dihydrochloride is also a potent AChE inhibitor with IC 50 s of 22 nM and 120 nM for electric eel and human AChE , respectively.