BOS-475

BOS-475 (also referred to by the code BOS1728515 in some contexts) is a small molecule inhibitor of the G protein-activated inward rectifier potassium channel (GIRK1/4), which conducts the acetylcholine-activated inward rectifier potassium current (I(KACh)). Developed by Boston Pharmaceuticals in partnership with CVasThera, the drug is designed as an atria-selective treatment for atrial fibrillation (AF). By specifically targeting GIRK channels, which are predominantly expressed in the atria and activated during AF, BOS-475 aims to prolong the atrial refractory period and terminate arrhythmias without affecting ventricular repolarization. This mechanism offers a potential safety advantage over traditional class III antiarrhythmics by reducing the risk of ventricular proarrhythmia. The program was originally licensed from Sanofi.