An ester of ArOH according to the formula R—X—CO—OAr, wherein ArOH is a pharmaceutically
active compound selected from the group consisting of SN-38, PI-103,
etoposide and fenretinide, wherein a) R is a residue of
cholesterol, sitosterol, SN-38, PI-103,
etoposide or fenretinide and X is O—CO-L, wherein L is either a direct bond or a linking group including a branched or unbranched hydrocarbyl
moiety that may optionally include in-chain or pendant
heteroatom substituents and / or cyclic moieties; b) R—X—CO-0 is an all-trans retinoate radical or the 9-cis or 13-cis isomer thereof; or c) R—X— is a branched or unbranched, saturated or unsaturated hydrocarbyl
moiety comprising at least 5 carbon atoms and optionally including at least one in-chain or pendant
heteroatom substituent and / or cyclic
moiety. A dispersion of nanoparticles in an
aqueous medium includes nanoparticles including an ester of ArOH according to the formula R—X—CO—OAr wherein ArOH is a pharmaceutically
active compound in which Ar is a substituted or unsubstituted
aryl or heteroaryl radical, and wherein R is as defined above or R—X—CO-0 is as defined above. The ester or dispersion may be used to treat a diagnosed medical condition in a patient.