QT interval prolongation: preclinical and clinical testing arrhythmogenesis in drugs and regulatory implications.

The assessment about the proarrhythmic risk associated with a particular drug is a major requirement for drugs under development, since many drugs have been withdrawn from market or got under strict pharmacological vigilance because of such a risk. Predicting the development of a life-threatening arrhythmia is a hard task but, in the case of TdP ("Torsades de Pointes"), there are some useful markers. Among them, the prolongation of the QT interval and its heart rate correction (QTc) are the most remarkable. Actually, QT prolongation is considered the surrogate marker of TdP from the clinical and regulatory standpoint. ICH E14 provides recommendations to sponsors concerning the design, conduct, analysis, and interpretation of clinical studies to assess the potential of a drug to delay cardiac repolarization. The regulatory information about preclinical safety evaluation is contained in ICH S7B. Both guidelines have been a matter of intense debate. False negative and false positive results have been found within the preclinical and clinical field. There still are grey areas in which further research would be necessary. Improvement of tools that may contribute to complement the data from the human ether-a-go-go-related gene HERG channel and QT/QTc studies, such as concentration-QT relationship (CQT) studies and other innovative techniques, will be more than welcome.