Sapropterin dihydrochloride (subsequently referred to as sapropterin) (Kuvan®) was approved by the FDA for the treatment of hyperphenylalaninemia in 2007. Preclinical and clinical studies and post-marketing surveillance have not demonstrated any specific cardiovascular concerns with sapropterin (Kuvan®). Nonetheless, nonantiarrhythmic drugs may have the potential to prolong QT interval, leading to potentially fatal ventricular tachycardias, including torsades de pointes. As part of the post-marketing commitment, a thorough QT/QTc study will be conducted according to ICH guidelines.