hERG Inhibition Assay

The hERG Inhibition Assay: predictive, sensitive & rapid

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Whole-cell current amplitude and kinetics measurements verify the result of potential interactions of a test article with the product of the hERG gene, a human ion channel responsible for the IKr repolarizing current. IKr current inhibition has been shown to prolong the cardiac action potential, a phenomenon associated with increased risk of arrhythmia. IKr inhibition accounts for the vast majority of known cases of drug-induced QT-prolongation.

hERG1

Highlights:

•GLP-compliant manual patch-clamp
•Conducted at physiological temperature
•Part of the core battery of Safety Pharmacology tests required for IND submission
•Screens (non-GLP, faster study design) also available

 

Assay description:

Rapid delayed rectifying potassium (IKr) current inhibition assay

Cell line type:

HEK293 or CHO cells stably transfected with the human ERG (hERG) gene

Technique:

Manual patch-clamp, whole-cell configuration

GLP compliance:

Pre-IND (GLP-compliant) or exploratory designs (screen = non-GLP compliant)

Rationale:  

Part of the core battery of Safety Pharmacology tests required for IND submission Whole-cell current amplitude and kinetics measurements verify the results of the interactions of a test article with the product of the hERG gene, a K+-selective ion channel responsible for the IKr repolarizing current. IKr current inhibition has been shown to prolong the cardiac action potential, a phenomenon associated with increased risk of arrhythmia. IKr current inhibition accounts for the vast majority of known cases of drug-induced QT- prolongation.

Study Outline:

  • Number of cells exposed to the test article: 7 (screens: 3)
  • Number of concentrations of test article: 4 (screens: 3)
  • Method of test article exposure: cumulative concentrations in closed-circuit perfusion, or constant perfusion of individual concentrations
  • Voltage pulse: partial current-voltage relationship
  • A study includes positive and vehicle controls as well as a reference article

Study Outcome:

  • A quantitative assessment of IKr current inhibition
  • Determination of the IC50 value (if applicable)
  • Analysis of both amplitude and current kinetics as indicators of inhibition
  • FDA-ready hard copy  and e-report for electronic IND submission
  • Holistic interpretation of a positive signal, considering all other data generated

Recommended reading:

  1. Shah RR., Drug-induced QT interval prolongation-regulatory guidance and perspectives on hERG channels studies., Novartis Foundation Symp., 2005; 266:251-80.
  2. Sanguinetti MC. Mitcheson JS., Predicting drug-hERG channel interactions that cause acquired long QT syndrome., Trends in Pharmacological Sciences., 2005; 26(3): 119-24.