SCN5A and Prolonged QT interval: Some studies showed that ribociclib is capable of down-regulating the expression of KCNH2 (which encodes for the potassium channel Herg) and up-regulating the expression of SCN5A and SNTA1 (which encode for the sodium channels syntrophin-α1 and Nav1.5), which are the genes associated with long QT syndrome.