Structure-Affinity Relationships (SARs) and Structure-Kinetics Relationships (SKRs) of Kv11.1 Blockers.

Kv11.1 (hERG) blockers with comparable potencies but different binding kinetics might display divergent pro-arrhythmic risks. In the present study, we explored structure-kinetics relationships in four series of Kv11.1 blockers next to their structure-affinity relationships. We learned that despite dramatic differences in affinities and association rates, there were hardly any variations in the dissociation rate constants of these molecules with residence times (RTs) of a few minutes only. Hence, we synthesized 16 novel molecules, in particular in the pyridinium class of compounds, to further address this peculiar phenomenon. We found molecules with very short RTs (e.g., 0.34 min for 37) and much longer RTs (e.g., 105 min for 38). This enabled us to construct a k on-k off-KD kinetic map for all compounds and subsequently divide the map into four provisional quadrants, providing a possible framework for a further and more precise categorization of Kv11.1 blockers. Additionally, two representative compounds (21 and 38) were tested in patch clamp assays, and their RTs were linked to their functional IC50 values. Our findings strongly suggest the importance of the simultaneous study of ligand affinities and kinetic parameters, which may help to explain and predict Kv11.1-mediated cardiotoxicity.