Comparisons of hERG data for 30 drugs generated by automated and manual patch clamp systems by the same laboratory

Abstract

hERG block is the most common mechanism of drug-induced QT_C prolongation and the rare but potentially fatal arrhythmia Torsade de Pointes. Accordingly, hERG results are used to support first-in-human studies (ICH S7B), and new pathways have been developed to use hERG data generated following best practices (ICH S7B Q&A 2.1) to complement clinical QT_C studies and to inform labeling (ICH E14 Q&As 5.1 and 6.1). High-throughput, automated patch clamp systems (APC) can efficiently evaluate hERG block for new drug candidates. However, elements in APC experimental design and conduct, such as the use of non-physiological fluoride and recording temperature, have raised concerns regarding their impact on hERG pharmacology. This study compared hERG block potencies for 30 drugs collected using an APC to the same laboratory's manual patch clamp (MPC) data generated following best practices. MPC data are presented in a companion abstract by Alvarez-Baron et al. Recordings were conducted using SyncroPatch384 at 36 °C and 21 °C using fluoride-based internal solution and the same voltage protocol as the MPC. There was no systematic difference in IC₅₀s between the 36 °C APC and 37 ± 2 °C MPC data. Twenty-seven drugs (90 %) had APC IC₅₀ values within a range closely matching the MPC data. Reducing nonspecific binding by adding BSA or saturating binding sites with repeated drug applications lowered these drugs' IC₅₀s, suggesting that the largest differences are attributed to more drug loss in the APC experiments. Comparisons of the 36 °C and 21 °C APC data showed no systematic effect of temperature. Data from APC and MPC at near physiological temperature align well. Ongoing experiments are testing whether hERG data variability, determined by repeatedly obtaining IC₅₀ for the same drug, is drug-specific. The IC₅₀s variability needs to be accounted for when using the hERG safety margin to identify the likelihood of clinical QT_C prolongation. Empirically determining this using MPC is not practical. The ability to determine hERG data variability for different drugs rapidly is an advantage of APC that could lead to clearer comparisons of hERG safety margins of the investigational product and reference products.