By Fineline Cube 
German pharmaceutical giant Bayer (ETR: BAYN) this week initiated a Phase I clinical study for its BAY 3670549, a G-protein-coupled inwardly rectifying potassium channel 4 (GIRK4) inhibitor. The drug is designed to help control the electrical activity of heart cells in patients with atrial fibrillation (AFib). This investigative approach aims to enable rapid cardioversion to normal sinus rhythm, allowing immediate treatment without the need for anesthesia/sedation and electrical shock, and significantly reducing patients’ time spent in hospital.
Mechanism of Action
GIRK4 channels are specialized proteins that regulate the electrical activity of heart cells by facilitating the flow of potassium ions (K+) in response to the neurotransmitter acetylcholine (ACh). This mechanism is particularly crucial during the later phases of the heart’s electrical signaling, specifically during the atrial effective refractory period (AERP). Increased activity of these channels shortens the AERP in the atria (the upper chambers of the heart), thereby reducing the recovery time after each heartbeat. This alteration in recovery time can contribute to the onset and persistence of AFib.
Clinical Trial Objectives
The Phase I study of BAY 3670549 will assess the safety, tolerability, and pharmacokinetics of the drug in healthy volunteers. The ultimate goal is to develop a treatment that can rapidly restore normal heart rhythm in patients with AFib, improving clinical outcomes and patient quality of life.-Fineline Info & Tech