Abstract: The present invention relates to a particularly advantageous antibody, antibody fragment or derivative thereof, which specifically binds to/interacts with at least one epitope of the extracellular or intracellular domain or the mammalian EAG1 ion channel and to nucleic acid molecules encoding the same and to vectors comprising said nucleic acid molecules. The invention additionally relates to methods for the preparation of said antibody, antibody fragments or derivatives thereof and to pharmaceutical compositions comprising the same. Furthermore, the use of said antibody, antibody fragment or derivative thereof and also diagnostic compositions comprising said components are disclosed in the specification. The invention also relates to a method of assessing for the presence of EAG1 expressing cells and for a method of blocking EAG1 function in said cells. The invention further relates to a method of treating diseases with the help or said antibody or antibody fragment or derivative thereof.