Biological Applications of Ti(IV) Complexes

Cisplatin is a widely used platinum-based metallo-chemotherapeutic drug that is considered an efficient treatment mainly for testicular and ovarian cancers. However, its narrow activity range and severe side effects trigger studies of other potent transition metal complexes. Two titanium (IV) anti-cancer agents that have been previously studied extensively as cisplatin alternatives are titanocene dichloride and budotitane. Despite their high activity, these complexes failed clinical trials mainly due to their poor water stability and formation of unidentified aggregates in water solutions. Our research group focuses on development of new better-suited families of anti-tumor Ti(IV) complexes lacking Cp or diketonato ligands, and their investigation as anti-tumor agents. We recently reported the synthesis, characterization, and cytotoxicity of “salan” type Ti(IV) complexes. The well-defined hydrolytic behaviour, high stability, and high cytotoxicity of these compounds are strongly correlated to their structure. This enables fine tuning of complex properties by structural modifications.

Herein we elaborate on the investigation of these salan titanium(IV) compounds. The correlation between the complex properties: structure, hydrolytic stability and cytotoxicity will be discussed, revealing insights on the biological mechanism of their cytotoxicity, suggesting an apoptotic cell death pathway.

Additionally, further biological evaluation is presented, evincing that these compounds are markedly more active than cisplatin towards human and murine cancer-derived cell lines, including colon, ovarian, lung, cervix, pancreas, leukemia, skin and breast, with activity also against cisplatin-resistant and multi-drug-resistant cells, and with minor effect on primary murine cells. In vivo experiments are now under way to determine both safety, as well as the anti-cancer activity of these complexes.