Disclosed is the compound 1-{ 5-Phenyl-4-[(pyridin-2-ylmethyl)-amino]-thieno[2,3-d]pyrimidin-2-yl} -piperidine-3-carboxylic acid (2-hydroxy-ethyl)-amide and enantiomers thereof. Also disclosed are pharmaceutical compositions comprising the compounds and their use as potassium channel inhibitors in the treatment of arrhythmia.