This disclosure provides mixtures of beta-cyclodextrin molecules substituted at one or more hydroxyl positions by hydroxypropyl groups, the mixture optionally including unsubstituted beta-cyclodextrin molecules, for use as a pharmaceutically active ingredient; methods of making such mixtures; methods of qualifying such mixtures for use in a pharmaceutical composition suitable for intrathecal or intracerebroventricular administration; pharmaceutical compositions suitable for intrathecal or intracerebroventricular administration comprising such mixtures; and methods of using the pharmaceutical compositions for treatment of Niemann-Pick disease Type C.