Optimization of Cardiac CiPA Targets (hCav1.2 and hKCNQ1/hminK) on the QPatch HT Automated System

Drug-induced QT interval prolongation, ventricular arrhythmia and sudden death are one of the leading causes for drug withdrawal from the market or denied regulatory approval. Preclinical profiling for off-target cardiac ion channel interactions using The Comprehensive in vitro Proarrhythmia
Assay (CiPA) paradigm has been initiated to overcome drug attrition due to hERG inhibition only. The aim is to improve the prediction of a drug’s proarrhythmic liability for the pharmaceutical industry. This new paradigm includes a panel of in vitro assays that integrates effects of the test compounds on several cardiac ion channels. Voltage-gated ion channels in this panel, particularly hCa_V1.2 and hKCNQ1/hminK, exhibit rapid
activities decrease when contact between membrane and cytosol is disrupted upon patch excision (run-down). The loss of channel activity without pharmacological interaction poses a challenge for developing accurate, precise and robust assay yielding high success rate, minimal current run-down and reliable pharmacological results. In the present study, hCa_V1.2 and hKCNQ1/hminK cardiac ionic currents were validated on QPatch HT patch clamp system with the specific focus on preventing current run-down. The results demonstrate suitability of these assays for screening and profiling of drug effects by significantly reducing run-down (<20%) by optimizing protocol parameters. Reference pharmacology was
assessed for Ca_V1.2 (Nifedipine IC₅₀ =144nM) and  hKCNQ1/hminK (Chromanol 293B IC₅₀ =12.3μM). The optimized assays for hCa_V1.2 and hKCNQ1/hminK on the QPatch are able to provide data that is comparable to manual patch clamp, which allows the assessment of a novel compounds proarrhythmic risk.