15.10.2020 | Webinar: Evaluation of possible proarrhythmic potency: variability of IC50 values of drugs under different conditions and in different platforms
Date: October 15. 2020
Dr. Péter Orvos (University of Szeged)
This is an on-demand webinar from Nan]i[on and Friends 2020.
The conventional microelectrode technique and the manual patch clamp method offer direct, information-rich, and real-time in vitro technologies to study proarrhythmic effect of drugs and drug candidate compounds. Although providing excellent data quality, these tests are complicated, time consuming and expensive for the large numbers of compounds. Automated patch-clamp platforms are mainly used with stably expressing cell lines and suitable for rapid and high-quality pharmacological investigation of drug candidates. The Comprehensive in Vitro Proarrhythmia Assay (CiPA) was initiated to further improve these preclinical drug safety paradigms. However, some evidence indicates that the different proarrhythmic pharmacological assays result in contradictory outcomes raising serious questions regarding their predictability for in vivo situations including clinical settings. IC50 values may varied between platforms, therefore, aim of our study was to compare the effect of proarrhythmic compounds on hERG and IKr currents and on cardiac action potential. The hERG current was measured by using both automated and manual patch clamp methods on HEK293 cells. The native ion current (IKr) were recorded from rabbit ventricular myocytes by manual patch clamp technique.
Dofetilide, cisapride, sotalol, terfenadine and verapamil were tested in hERG assay at both room temperature and 37°C with Patchliner. All these compounds were more potent at physiological temperature and therefore, it is a desirable option to study hERG currents at physiological temperature. To evaluate the prognostic value of hERG assay these agents were subjected for further investigations. The IKr current blocking capability of the compounds was tested on rabbit ventricular myocytes with manual patch clamp method at 37°C. The corresponding IC50 values of dofetilide, cisapride and verapamil were in good agreement with IC50 values obtained with Patchliner in hERG assays. As sotalol and terfenadine have stronger effect on IKr measured by manual patch clamp method compared with hERG automated patch clamp experiments, the effects of these drugs on hERG current using manual patch clamp technique were also investigated to study how the potency of these drugs are influenced by the experimental techniques themselves. In contrast with the hERG automated patch clamp assays, the effects of sotalol and terfenadine on hERG current were stronger measured by the manual patch-clamp technique.
In conclusion, results obtained with automated patch-clamp equipment in HEK-hERG cells usually show a reasonable conformity with outcomes of IKr current experiments. The Patchliner system used in our study is well suited to perform safety pharmacological studies. Variability of IC50 values of drugs in different platforms observed in certain cases, which could have been caused by the lack of continuous flow of compound-containing solutions.