Effects of water content on physical and chemical stability of tablets containing an anticancer drug TAT-59.

(E)-4-[1-[4-[2-(Dimethylamino)ethoxy]phenyl]-2-(4-isopropyl) phenyl]-1-butenyl]phenyl monophosphate (TAT-59) is a new drug for the treatment of breast cancer. Physical and chemical stability of a tablet consisting of TAT-59 powder and a few excipients (Formulated tablet), a tablet consisting of only TAT-59 powder (TAT-59 tablet) and TAT-59 powder itself was evaluated based on water content, tensile strength, porosity, the amount of TAT-59 and its hydrolysis product, DP-TAT-59. The water content of Formulated tablet increased with relative humidity (RH), whereas that of TAT-59 tablet and TAT-59 powder scarcely changed. The equilibrium water content of Formulated tablet was much greater than that of the TAT-59 tablet or TAT-59 powder due to adsorbed moisture by the excipients. The tensile strength and porosity of Formulated tablet decreased and increased linearly, respectively, with increasing water content. The degradation rate of TAT-59 decreased in the following order: Formulated tablet > TAT-59 tablet > TAT-59 powder. The relationship between equilibrium water content and degradation rate of the Formulated tablet was determined by the Carstensen equation, in which the interaction order between the drug and water content was 1.9, and the degradation of TAT-59 in Formulated tablet was related to water content. Thus, it was found that the degradation of TAT-59 was accelerated by compression and addition of excipients.