QTc shortening with a new investigational cancer drug: A brief case study

IntroductionBAY-79 is an inhibitor of receptor tyrosine kinases with high selectivity versus other kinases. Species scaling, complicated by nonlinear pharmacokinetics, predicted a Cmax.u of 36–178 nmol/L at the human efficacious exposure.MethodsPreclinical cardiovascular safety pharmacology studies assessed currents (hERG, INa), action potential (AP, rabbit Purkinje fiber), hemodynamic/ECG parameters (anesthetized Beagle dogs, intravenous infusion), and proarrhythmic potential (rabbit Langendorff heart Screenit™ model).ResultsBoth hERG K+ current and hNav1.5 Na+ current were inhibited with low potency (IC20 > 10 μmol/L). Purkinje fiber APs remained unaffected at 10 μmol/L, but at 100 μmol/L displayed reverse use-dependent AP duration shortening (APD90–33% at 1 Hz) and triangulation. Infusion of BAY-79 into anesthetized dogs was associated with moderate hemodynamic effects (increased heart rate and diastolic blood pressure, reduced stroke volume) and marked QTcV shortening (− 25 ms) starting at ∼ 0.65 μmol/L (unbound); QRS was not changed. Assessment of the proarrhythmic potential in the Screenit™ model showed effects (AP duration shortening, triangulation, instability, reduced coronary flow, slowed conduction) at ≥ 30 μmol/L (0.5 h/concentration) and at 3 μmol/L with longer exposure (2.5 h/concentration).DiscussionBAY-79 at plasma concentrations slightly higher than those predicted to be therapeutically efficacious in humans is associated with QTc shortening in dogs but of unclear mechanistic basis. The QTc shortening associated proarrhythmic potential of BAY-79 together with other considerations finally resulted in an unfavorable risk–benefit assessment.