The present invention relates to a composition comprising a tricyclic indole compound. The composition has a higher purity and better impurity profile than known compositions comprising said tricyclic indole compound and as a consequence has superior properties, particularly when said compound is destined for use in vivo as a therapeutic or diagnostic agent. Also provided by the present invention is a method to make the composition of the invention, a pharmaceutical composition comprising the composition of the invention, and use of the composition of the invention in a medical method.
