USA – Finding a Better Test for Predicting the Risk Drugs Pose to the Heart

FDA research has laid the groundwork for replacing the thorough QT (TQT) study, a costly clinical trial required to determine whether new drugs cause abnormal heart rhythms (arrhythmias), with a more precise, less costly, and faster approach to testing. Drugs with a high risk of causing arrhythmias will continue to be screened out, while potentially safe and effective drugs that might not have passed the TQT study will continue in development.

Several drugs were removed from the market in the 1990s and early 2000s because of un- or under-appreciated risk of a fatal arrhythmia. Beginning in 2005, most new drug compounds delivered through the bloodstream needed to pass a separate clinical trial, in addition to the traditional (Phases I-III) clinical trials that FDA required for drug development. This additional trial, called the TQT study, was added to determine whether the drug could cause a fatal heart arrhythmia.

In a TQT study, healthy study participants are given a high dose of a candidate drug, and their heart activity is recorded on an electrocardiogram (ECG). If the drug prolongs the average time between the Q and T waves on the ECG more than 10 milliseconds, additional patient monitoring is required in clinical studies and development of the drug may stop.

Since 2005, approximately 450 TQT studies have been performed, costing drug developers more than $1 billion. No new drugs have been removed from the market because of arrhythmia risk since the test became mandatory, but it is not clear that the TQT approach identifies only the drugs with true risk…