A process for the preparation of a camsylate salt ((1S)-(+)-10 camphorsulfonic acid) of (1r, 1' R, 4R)- 4-methoxy-5"-methyl-6' -[5-(prop-1-yn-1-yl)pyridin- 3-yl]-3' H-dispiro[cyclohexane-1, 2' -inden-1' 2' -imidazole]-4"-amine is disclosed as well as pharmaceutical compositions containing the salt and therapeutic uses of the salt for treating A?related pathologies such as Alzheimer' s Disease, Down' s Syndrome, ?amyloid angiopathy and conditions such as dementia including dementia of mixed vascular and degenerative origin, pre-senile dementia, senile dementia and dementia associated with Parkinson' s Disease, progressive supranuclear palsy or cortical basal degeneration.