Hit-to-lead investigation of a series of novel combined dopamine D2 and muscarinic M1 receptor ligands with putative antipsychotic and pro-cognitive potential.

We describe the discovery of a series of compounds based on 1-{3-[4-(2-oxo-2,3-dihydro-benzoimidazol-1-yl)-piperidin-1-yl]-propyl}-3,4-dihydro-1H-quinolin-2-one (3), showing combined D2 receptor affinity and M1 receptor agonism. Based on a strategy of controlling logP, we herein describe a hit-to-lead investigation with the aim of retaining the combined D2/M1 profile, while removing the propensity of the compounds to inhibit the hERG channel, as well as at obtaining acceptable pharmacokinetic properties. Although a SAR was evident for all four parameters in question, it was not possible to separate hERG channel inhibition and D2 receptor affinity by this effort; whilst it was feasible to obtain compounds with M1 receptor agonism, acceptable clearance, and weak hERG inhibition.