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August 12, 2026The Journal of General Physiology

A hERG blocker facilitates K+ channel current by promoting pore opening while blocking

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Why the study?

Many hERG-blocking drugs can cause long QT syndrome and life-threatening arrhythmias, but the molecular mechanisms determining this risk remain unclear.

Population

hERG voltage-gated K+ channels

Comparison

Nifekalant block and facilitation effects

Design

Kinetic and atomistic modeling with voltage-clamp measurements

Key result

Nifekalant facilitates hERG K+ channel current through an agonism-while-blocking mechanism, which may contribute to the relative safety of certain hERG blockers.

Authors

SDSteffen S. DockenMMMatthew James MarquisKNKhoa Ngo

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Overview

May refine arrhythmia risk models for hERG blockers; leaves open clinical relevance of facilitation.

Key Points

  • To determine whether an agonism-while-blocking mechanism explains how the antiarrhythmic drug nifekalant facilitates hERG channel current to counteract arrhythmogenic channel blockade.
  • Developed rate-theory kinetic models to define the theoretical properties required for an agonism-while-blocking mechanism to generate current facilitation.
  • Constructed atomistic structural models to predict the binding interactions of nifekalant with the hERG conduction pore and intracellular gate.
  • Conducted voltage-clamp electrophysiology recordings to quantify nifekalant-mediated block and facilitation in hERG channels.
  • Atomistic modeling predicted that nifekalant occupies the hERG conduction path while directly modulating and opening the intracellular conduction gate.
  • Voltage-clamp measurements confirmed that open-yet-blocked channels rapidly unblock under permissive conditions to generate supranormal hERG potassium current facilitation.

Structured PICO

P
Population
hERG channels (computational models and voltage-clamp measurements)
I
Intervention
Nifekalant (and other hERG blockers)
O
Outcome
hERG current facilitation and channel gating mechanismssurrogate

An agonism-while-blocking mechanism explains how certain hERG blockers like nifekalant induce current facilitation, which may counteract their arrhythmogenic potential.

Cite This Study

Docken et al. (2026) studied Long QT syndrome and cardiac arrhythmias. Nifekalant (hERG blockers) was evaluated on hERG current facilitation and channel gating mechanisms. Nifekalant facilitates hERG K+ channel current through an agonism-while-blocking mechanism, which may contribute to the relative safety of certain hERG blockers.

synapsesocial.com/papers/6a971c0ca8463d90298998f4https://doi.org/10.1085/jgp.202614015
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