hKV4.3 assays
hKV4.3
Since the Kv4.3 channel encoding for Ito current, plays an important role in the early stage of cardiac action potential repolarisation, a pharmacological reduction of the Ito current may delay the repolarisation process and may lead to QT interval prolongation. Thus the Kv4.3 potassium channel represent a specific target for the cardiac safety assessment.
hKV4.3 assays & Preclinical safety studies
At the cellular level, gain of the transient outward depolarizing current (Ito) conducted by the KCND3-encoded Kv4.3 α-subunit is hypothesized to result in an outward shift in current, heterogenous loss of the action potential dome, ST segment elevation on ECG, local re-excitation via phase II reentry, and the initiation of polymorphic ventricular tachycardia or ventricular fibrillation.
hKV4.3 assays & Preclinical safety studies
• Threshold concentration of hKV4.3 blockade or activation
• Leading to the determination of the safety range versus efficacious concentration
• You obtain your safety margin
Automated Patch Clamp
Technique
- Chinese Hamster Ovary CHO cells
- Experiment conducted at room temperature or at physiological temperature (35°C)
- Up to 6 increasing concentrations of test compound or biologic.
Measured parameters
- Amplitude of the peak current upon depolarization to +40mV (pA)
- Amplitude of the base current at –80mV (pA)
- Ion current amplitude measurement
- Inhibition of Kv4.3 peak current amplitude (%)
- IC50 value (at least 4 concentrations required)
Main adventages
- High throughput screening
- Cost effective
- Fast process to delivery results
- Perfect at earliest stages
- Design protocol could be adapted
Manual Patch Clamp
Technique
- Chinese Hamster Ovary CHO cells
- Experiment conducted at room temperature or at physiological temperature (35°C)
- Up to 5 increasing concentrations of test compound tested independently
- At least 3 treated cells are recommended
Measured parameters
- Amplitude of the peak current upon depolarization to +40mV (pA)
- Amplitude of the base current at –80mV (pA)
- Ion current amplitude measurement
- Inhibition of Kv4.3 peak current amplitude (%)
- IC50 value (at least 4 concentrations required)
Main adventages
- Technically robust
- Highly informative (more accurate IC50 value)
- Strongly replicable
- Design protocol could be adapted
Stimulation protocol
Typical effects of flecainide effects on Ito current recorded from CHO cells.
Reference compounds
Reference CompoundsIC₅₀
Flecainide19.6 µM
