The cardiac late Na+ current (late INa) generates persistent inward currents throughout the plateau phase of the ventricular action potential and is an important determinant of repolarisation rate, EADs and arrythmia risk¹. As inhibition of late INa can offset drug effects on hERG and other repolarising K⁺conductances, it is one of the key cardiac channels in the Comprehensive in vitro Pro-arrythmia Assay (CiPA) panel being developed by the FDA to improve human clinical arrythmia risk assessment²̛ ³.

Cardiac toxicity remains the leading cause of new drug safety side-effects. Current preclinical cardiac safety assays rely on in vitro cell-based ion channel assays and ex vivo and in vivo animal models⁽¹⁾. These assays provide an indication of acute risk but they do not always predict the effect of chronic compound exposure, as recently seen with oncology drugs. Therefore, new assays are required to characterise chronic structural and functional effects in human cells earlier in drug discovery. Impedance-based technology can provide more accurate chronic cardiotoxicity measurements in an efficient manner using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs).