Pharmacological and electrophysiological characterization of nine, single nucleotide polymorphisms of the hERG-encoded potassium channel.

BACKGROUND AND
PURPOSE: Potencies of compounds blocking K(V)11.1 [human ether-ago-go-related gene (hERG)] are commonly assessed using cell lines expressing the Caucasian wild-type (WT) variant. Here we tested whether such potencies would be different for hERG single nucleotide polymorphisms (SNPs). EXPERIMENTAL APPROACH: SNPs (R176W, R181Q, Del187-189, P347S, K897T, A915V, P917L, R1047L, A1116V) and a binding-site mutant (Y652A) were expressed in Tet-On CHO-K1 cells. Potencies [mean IC(50); lower/upper 95% confidence limit (CL)] of 48 hERG blockers was estimated by automated electrophysiology [IonWorks HT (IW)]. In phase one, rapid potency comparison of each WT-SNP combination was made for each compound. In phase two, any compound-SNP combinations from phase one where the WT upper/lower CL did not overlap with those of the SNPs were re-examined. Electrophysiological WT and SNP parameters were determined using conventional electrophysiology. KEY
RESULTS: IW detected the expected sixfold potency decrease for propafenone in Y652A. In phase one, the WT lower/upper CL did not overlap with those of the SNPs for 77 compound-SNP combinations. In phase two, 62/77 cases no longer yielded IC(50) values with non-overlapping CLs. For seven of the remaining 15 cases, there were non-overlapping CLs but in the opposite direction. For the eight compound-SNP combinations with non-overlapping CLs in the same direction as for phase 1, potencies were never more than twofold apart. The only statistically significant electrophysiological difference was the voltage dependence of activation of R1047L. CONCLUSION AND IMPLICATIONS: Potencies of hERG channel blockers defined using the Caucasian WT sequence, in this in vitro assay, were representative of potencies for common SNPs.