GAP-134 (also known as Danegaptide) is a dipeptide mimetic compound with the chemical name Z-D-Ala-L-Pro-D-Arg-H. It functions as a highly selective and potent gap junction modifier. Its primary mechanism of action involves enhancing gap junction communication between cardiomyocytes, which is believed to stabilize the electrical conduction in the heart. This compound was developed as a potential therapeutic agent for the prevention of cardiac arrhythmias, specifically atrial fibrillation, following cardiac surgery or myocardial infarction. By improving intercellular coupling, it aims to reduce the dispersion of action potential duration and suppress the initiation and maintenance of re-entrant arrhythmias. It has progressed through preclinical studies and Phase II clinical trials for these indications. As a synthetic dipeptide derivative, GAP-134 represents a class of biologically active peptide mimetics designed for targeted cardiovascular therapy. Its development highlights the application of peptide chemistry in creating novel pharmacological agents for unmet medical needs in cardiology.