A camsylate salt 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, pharmaceutical compositions containing the salt and therapeutic uses of the salt for treating Aβ-related pathologies such as Alzheimer's Disease, Down's syndrome, β-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.