Characterization of A-935142, a hERG enhancer, in the presence and absence of standard hERG blockers.

Xiaoqin Liu, James T Limberis, Zhi Su, Kathryn Houseman, Gilbert J Diaz, Gary A Gintant, Bryan F Cox, Ruth L Martin

Index: Life Sci. 90(15-16) , 607-11, (2012)

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Abstract

In a previous study we found that A-935142 enhanced hERG current in a concentration-dependent manner by facilitating activation, reducing inactivation, and slowing deactivation (Su et al., 2009). A-935142 also shortened action potential duration (APD90) in canine Purkinje fibers and guinea pig atrial tissue. This study focused on the combined effects of the prototypical hERG enhancer, A-935142 and two hERG current blockers (sotalol and terfenadine).The whole-cell voltage clamp method with HEK 293 cells heterologously expressing the hERG channel (Kv 11.1) was used.A-935142 did not compete with 3H-dofetilide binding, suggesting that A-935142 does not overlap the binding site of typical hERG blockers. In whole-cell voltage clamp studies we found: 1) 60 μM A-935142 enhanced hERG current in the presence of 150 μM sotalol (57.5±5.8%) to a similar extent as seen with A-935142 alone (55.6±5.1%); 2) 150 μM sotalol blocked hERG current in the presence of 60 μM A-935142 (43.5±1.5%) to a similar extent as that seen with sotalol alone (42.0±3.2%) and 3) during co-application, hERG current enhancement was followed by current blockade. Similar results were obtained with 60 nM terfenadine combined with A-935142.These results suggest that the hERG enhancer, A-935142 does not compete with these two known hERG blockers at their binding site within the hERG channel. This selective hERG current enhancement may be useful as a treatment for inherited or acquired LQTS (Casis et al., 2006).Copyright © 2012 Elsevier Inc. All rights reserved.