BAY-3670549

BAY-3670549 is an investigational, highly selective small molecule inhibitor of the G-protein-coupled inwardly rectifying potassium channel 4 (GIRK4, also known as Kir3.4). Developed by Bayer AG through a strategic research alliance with the Broad Institute of MIT and Harvard, the drug is designed for the treatment of atrial fibrillation (AFib). By selectively targeting GIRK4 channels, which are specialized proteins that regulate the electrical activity of heart cells in response to acetylcholine, BAY-3670549 aims to provide rapid pharmacological cardioversion to normal sinus rhythm. This approach potentially offers a fast-acting alternative to electrical cardioversion without the need for anesthesia, sedation, or electrical shock. As of May 2025, the compound is in Phase I clinical development, with studies evaluating its safety, tolerability, and pharmacokinetics in healthy participants.