The present invention provides a method for producing a cyclodextrin-panobinostat adduct, comprising : a) providing a first aqueous solution comprising a buffering agent, the solution having a pH in the range 2.0 to 4.0; b) dissolving panobinostat in said first aqueous solution to provide a second aqueous solution; and c) mixing said second aqueous solution comprising panobinostat with a third aqueous solution comprising a cyclodextrin to form a fourth aqueous solution comprising a cyclodextrin-panobinostat adduct. Also provided is an artificial cerebrospinal fluid (CSF) solution comprising the cyclodextrin-panobinostat adduct and medical uses of the cyclodextrin-panobinostat adduct, including in the treatment of brain tumours.