This invention relates to an oral formulation containing an effective amount of the compound of the following formula I:d-alpha-tocopheryl polyethylene glycol 1000 succinate (“TPGS”); and 2-(2-ethoxyethoxy)ethanol (“Transcutol”). R1 through R4 and n are defined herein. Also disclosed is a method of treating cancer by administering this formula to a subject orally.
