Stabilization of chimeric BR96-doxorubicin immunoconjugate

Chimeric BR96-doxorubicin conjugate (BR96-DOX) is an immunoconjugate designed to specifically target and kill certain tumor cells. The linker between the chimeric BR96 antibody and DOX is an acid-labile hydrazone group which was designed to undergo lysosomal hydrolysis to release DOX in vivo. Stability studies indicated that acid-catalyzed hydrazone hydrolysis was the major degradation route in vitro. Even under optimal conditions of pH and temperature, the stability of BR96-DOX in solution was not acceptable for long-term storage. Lyophilization of BR96-DOX in the presence of added sugars, such as lactose or sucrose, and subsequent storage of the lyophile under refrigeration significantly improved the stability. Therefore lyophilization appears to be a viable approach for achieving long-term stabilization of BR96-DOX.