Novel N-linked aminopiperidine inhibitors of bacterial topoisomerase type II: broad-spectrum antibacterial agents with reduced hERG activity

Novel non-fluoroquinolone inhibitors of bacterial type II topoisomerases (DNA gyrase and topoisomerase IV) are of interest for the development of new antibacterial agents that are not impacted by target-mediated cross-resistance with fluoroquinolones. Aminopiperidines that have a bicyclic aromatic moiety linked through a carbon to an ethyl bridge, such as 1, generally show potent broad-spectrum antibacterial activity, including quinolone-resistant isolates, but suffer from potent hERG inhibition (IC(50)= 3 μM for 1). We now disclose the finding that new analogues of 1 with an N-linked cyclic amide moiety attached to the ethyl bridge, such as 24m, retain the broad-spectrum antibacterial activity of 1 but show significantly less hERG inhibition (IC(50)= 31 μM for 24m) and higher free fraction than 1. One optimized analogue, compound 24l, showed moderate clearance in the dog and promising efficacy against Staphylococcus aureus in a mouse thigh infection model.