Predictor™ hERG Fluorescence Polarization Assay Kit

  • Non-radioactive - eliminates radioligands by utilizing a fluorescent hERG channel ligand (tracer)
  • Predictive - IC50 values accurately correlate with patch-clamp electrophysiology data
  • Add and read - perform high-throughput screening with a homogeneous assay format

Detect hERG binding without radioactivity

The Predictor™ hERG Fluorescence Polarization Assay Kit provides a set of validated components to perform hERG channel biochemical binding studies in the absence of radioligands. The assay was designed to identify potential hERG channel blockers by producing data that accurately correlates with patch-clamp electrophysiology studies. The assay is based on the principle of fluorescence polarization, where a red-shifted fluorescent tracer displays a high polarization when bound to the hERG channel and a low polarization when displaced by compounds that bind to the channel. Assay performance was validated with a panel of established hERG channel blockers (Figure 1). Results from the Predictor™ assay demonstrate a high correlation with those obtained from patch-clamp techniques (Table 1 and Figure 2).


To read the Frequently Asked Questions document and see the comparative data to patch clamp and radioligand binding using a 41 compound test set, please click here.


Figure 1. Concentration response curves for 10 known hERG channel blockers
generated by the Predictor™ hERG Fluorescence Polarization Assay Kit.
Following incubation of test compounds and Predictor™ kit components, fluorescence polarization is read
and plotted against compound concentration. IC50 values are determined by nonlinear fits of a sigmoidal dose response curve to the data.


Figure 2. Predictor™ assay compared to patch-clamp analysis. Values obtained from the Predictor™ hERG Fluorescence Polarization Assay are compared to those obtained using patch-clamp techniques. Linear regression analysis indicates that the data are highly correlated with the slope near unity. Dotted lines represent the 95% confidence intervals of the fit.
Compound IC50 (nM) Ki (nM)
Predictor™ assay Patch-clamp* [3H] - dofetilide binding*
Astemizole 2.7 1.2 1
Pimozide 7.2 18 6
Dofetilide 11 12 40
E-4031 17 48 20
Terfenadine 33 16 30
Haloperidol 187 174 90
Bepridil 279 550 170
Thioridazine 655 1250 510
Fluoxetine 2880 990 2230
Amitryptiline 8135 10000 *2440
*Patch-clamp values are derived from the following publications: Mol Pharmacol (1998) 54: 695; J Pharmacol Toxicol Methods (2004) 50: 187; Eur J Pharmacol (2002) 450: 37; Mol Pharmacol (1996) 49: 949; Lancet (2000) 355: 1825; Am J Physiol Heart Circ Physiol (2003) 284: H256.
[3H]-dofetilide binding values are derived from J Pharmacol Toxicol Methods (2004) 50: 187 (with 60 mM K+, except amitryptiline with 5 mM K+).

Table 1. Comparison of IC50 data from Figure 1 to established patch-clamp and radioactive binding data for each compound.

Kit Components

The kit contains suitable volumes of reagents to generate 400 data points.  The kit components are as follows:

  • Validated hERG membranes
  • hERG tracer red
  • Known hERG channel blocker
  • Assay buffer

The Predictor™ hERG kit is a homogeneous fluorescence assay that has a simple add-and-read format, supports high-throughput screening, and provides high accuracy, solvent tolerance, and stability over time.