Assessment of temperature‐induced hERG channel blockade variation by drugs

Abstract

Drug-induced QT prolongation has been reported in humans and animals. This potentially lethal effect can be induced by drugs interacting with a cardiac potassium channel, namely hERG (human ether-a go-go-related gene) leading to arrhythmia or torsade de pointes (TdP). Hence, in vitro evaluation of therapeutics for their effects on the rapid delayed rectifier current (IKr) mediated by the K(+) ion channel encoded by hERG is a valuable tool for identifying potential arrhythmic side effects during drug safety testing. Our objective was to evaluate the temperature-induced hERG channel blockade variation by human and veterinary drugs using the IonFlux 16 system. A panel of eight drugs was tested for IKr inhibition at both ambient (23 °C) and physiological (37 °C) temperatures at various concentrations using IonFlux 16, an automated patch clamp system. Our results established that both amiodarone (IC(50) = 0.56 μM at 23 °C and 0.30 μM at 37 °C) and β-estradiol (IC(50) = 24.72 μM at 23 °C and 8.17 μM at 37 °C) showed a dose-dependent IKr blockade with a higher blockade at 37 °C. Whereas, blockade of IKr by both ivermectin (IC(50) = 12.52 μM at 23 °C and 24.41 μM at 37 °C) and frusemide (IC(50) = 12.58 μM at 23 °C and 25.55 μM at 37 °C) showed a dose-dependent IKr blockade with a lower blockade at 37 °C. Gentamicin, enrofloxacin, xylazine and albendazole did not block IKr at both the assessed temperatures. Collectively, these results demonstrate that the effect of temperature variation should be taken into consideration during the evaluation of test drugs for their hERG channel blockade potential.

Interactions between amiodarone and the hERG potassium channel pore determined with mutagenesis and in silico docking

“…Previous experiments using Xenopus oocytes yielded an amiodarone IC 50 value for I hERG of 9.8 μM [10] whilst in mammalian expression systems I hERG IC 50 values between ∼26 and 300 nM were reported [12] , [13] , [14] , [16] , [17] . Amiodarone is highly lipophilic and for such agents the use of Xenopus oocytes can markedly underestimate blocking potency due to drug accumulation in the yolk sac [39] , [40] .…”

“…Similar to other drugs, amiodarone’s I hERG blocking potency is greater when the drug is tested on mammalian cell lines expressing hERG [11] , [12] , [13] , [14] , [15] . With mammalian expression systems, I hERG IC 50 values for amiodarone of between ∼26 and 300 nM were reported [12] , [13] , [14] , [16] , [17] and its metabolite desethyl-amiodarone (DEA) has been shown also to inhibit I hERG , with an IC 50 of ∼160 nM [14] . It is likely, therefore, that I hERG / I Kr blockade contributes to the acute clinical effects of amiodarone administration and that an inhibitory action of DEA additionally contributes to the chronic actions of the drug [14] .…”

Considerations for Drug Interactions on QTc Interval in Exploratory COVID-19 Treatment

“…Seriously ill patients often have comorbidities that can increase risk of serious arrhythmias. These include hypokalemia, hypomagnesemia, fever, 16 and an inflammatory state. 17 Mechanisms to minimize arrhythmia risk include: o In patients critically ill with COVID-19 infection, frequent caregiver contact may need to be minimized, so optimal electrocardiographic interval and rhythm monitoring may not be possible.…”

Novel screening techniques for ion channel targeting drugs

“…1E), and on the QPatch. [15][16][17] The temperature control feature on instruments such as Patchliner and Ionflux 18 can be used to record ion channel activity at physiological temperature, and on the Patchliner, fast changes in temperature can be used to activate temperature regulated ion channels such as TRPV1 19 and TRPV3…”