Abstract
We have developed procedures that consistently allow the procurement and experimental interrogation of human heart tissue preparations to reliably assess the toxicity risks of novel drugs. To further increase the throughput/scalability, we have now established novel protocols for the isolation of adult human primary cardiomyocytes (hCMs). To begin addressing the clinical relevance of the hCM preparation, we generated validation data with clinically well characterized positive and negative controls, including 6 torsadogenic (cisapride, clarithromycin, d,l-sotalol, dofetilide, domperidone, quinidine) and 3 non-torsadogenic drugs (mexiletine, ranolazine, verapamil) on contractility parameters using a digital, cell geometry measurement system (IonOptix™). All torsadogenic drugs, mexiletine and ranolazine, but not verapamil, increased time to 90% relaxation and therefore their QT-prolonging effect could be predicted in our hCM-based model. We also found that hCM-based model predicted the pro-arrhythmic potential of the 6 torsadogenic drugs. After-contraction (AC) incidence with cisapride, domperidone and quinidine was seen starting at the fETPC (free Effective Therapeutic Plasma Concentration), while sotalol, dofetilide and clarithromycin-induced ACs starting at 10-fold the fETPC. In contrast, mexiletine, ranolazine and verapamil induced no ACs up to the highest multiple of fETPCs tested in our study (53X, 100X and 222X, respectively). Dofetilide and sotalol, hERG channel blockers, have no effects on sarcomere shortening (SS), while multi-channel blockers, like cisapride, clarithromycin, domperidone, mexiletine, quinidine, ranolazine and verapamil, inhibited SS. Thus, our hCM-based model has the potential to simultaneously predict risk associated with inotropic activity and QT/pro-arrhythmia, and enables the generation of reliable and predictive human cardiotoxicity data at the preclinical stage.
