INNO-206 (DOXO-EMCH), an Albumin-Binding Prodrug of Doxorubicin Under Development for Phase II Studies

The (6-maleimidocaproyl)hydrazone derivative of doxorubicin (INNO-206, formerly DOXO-EMCH) is a prodrug of the anticancer agent doxorubicin which is selectively bound to the cysteine-34 position of endogenous albumin within a few minutes after intravenous administration planned for 2011. Preclinically as well as clinically, the albuminbound form of INNO-206 has a large AUC, a small volume of distribution and low clearance compared to doxorubicin, uptake in solid tumors being mediated by the pathophysiology of tumor tissue, characterized by angiogenesis, hypervasculature, a defective vascular architecture, and an impaired lymphatic drainage. The prodrug contains an acid-sensitive hydrazone linker allowing doxorubicin to be released either extracellularly in the slightly acidic environment often present in tumor tissue or intracellularly in acidic endosomal or lysosomal compartments after cellular uptake of the albumin conjugate by the tumor cell. INNO-206 shows significantly superior antitumor efficacy over free doxorubicin in a spectrum of preclinical tumor models. In a phase I study, INNO-206 showed a good safety profile at doses up to 260 mg/m2 doxorubicin equivalents. Although not the primary end point of the phase I study, INNO-206 was able to induce tumor regressions in breast cancer, small cell lung cancer and sarcoma. Phase II studies against gastric cancer, pancreatic cancer and sarcoma are planned for the end of 2010.