Background: Voltage-gated potassium channel KV4.2 (encoded by KCND2 gene) contributes to the cardiac transient outward potassium current (Ito1). This current is the main contributor to the repolarisation phase 1 of the cardiac action potential. The toxin AmmTx3, identified from the venom of the scorpion Androctonus mauretanicus, is a blocker of KV4.x channels, and have interesting therapeutic potential for neurological disorders due to its effect in cerebellar granule neurons. Its effects on cardiac KV4.2 channels remains unclear. Conclusion :AmmTx3 toxin can be chemically synthesized and used as a KV4.2 channel inhibitor to contributed to the better understanding of the exact role of Ito1 in cardiac electrophysiology. Those first results seem to be a promising evidence that AmmTx3 could a potential inhibitor of Ito current in early repolarisation syndrome.