Bayer has initiated a global Phase 2 clinical trial evaluating BAY 3670549, an investigational highly selective G-protein-coupled inwardly rectifying potassium channel 4 (GIRK4) inhibitor, as a potential treatment for Atrial Fibrillation (AFib).

The randomised, double-blind, placebo-controlled, parallel-group, multi-cohort Phase 2 study will assess the efficacy, safety and tolerability of BAY 3670549, along with its pharmacodynamic and pharmacokinetic properties, in adults with AFib who require electrical cardioversion.

BAY 3670549 is being investigated as a potential approach for rapidly restoring normal sinus rhythm by targeting GIRK4 channels, which play a role in regulating the electrical activity of heart cells. Bayer said the candidate could potentially offer an alternative to electrical cardioversion, which generally requires sedation or anaesthesia and hospital-based care.

The programme follows a completed first-in-human Phase I single-ascending-dose study, in which BAY 3670549 demonstrated a favourable safety and tolerability profile in healthy male and female participants. The candidate emerged from Bayer's strategic research collaboration with the Broad Institute.

“The start of the Phase 2 marks an important step in our commitment to redefining what may be possible in cardiovascular care, with GIRK4 inhibition carrying the potential to meaningfully advance the treatment of atrial fibrillation,” said Dominik Ruettinger, M.D., Ph.D., Head of Research and Early Development, Bayer Pharmaceuticals Division.

AFib is the most common sustained cardiac arrhythmia and is associated with an increased risk of stroke and heart failure. Electrical cardioversion remains an established treatment for restoring normal heart rhythm during acute AFib episodes, while currently available anti-arrhythmic drugs have limitations related to patient eligibility, efficacy and safety.

Bayer said the Phase 2 trial will provide further clinical data on BAY 3670549 and help determine its potential as a fast-acting treatment option for patients with AFib.