Moving beyond surrogate endpoints in cell therapy trials for heart disease.

Cell therapy for heart disease began clinically more than a decade ago. Since then, numerous trials have been performed, but the studies have been underpowered, focusing primarily on low-risk patients with a recent myocardial infarction. Many data have accumulated on surrogate endpoints such as ejection fraction, but few clinical conclusions can be drawn from such studies. We argue here that the time is right for targeting larger and/or higher-risk populations for whom there is some expectation of being able to influence mortality or rehospitalization.