Disclosed herein is a pharmaceutical composition comprising a compound of formula (Ia) or a pharmaceutically acceptable salt thereof, wherein the substituents are as defined with in the specification and wherein at least two of the five substituents are always hydrogen, at least one of the five is always nitro and at least one substituent positioned adjacent to a nitro is always iodo； a buffer； and a beta-cyclodextrin. Also disclosed is the used of said composition in the treatment of cancer.
