Light-Activated Metal Complexes that Covalently Modify DNA

Many drugs in current clinical use rely on mechanisms of action that involve damage to nucleic acids. While this has been a successful therapeutic approach for many years, the major limitation of these agents is systemic cytotoxicity, resulting from damage caused to healthy cells. Photoactive metal complexes offer the possibility of combining two successful treatment modalities for cancer and other diseases by providing DNA damage similar to that obtained with cisplatin, but in a spatially and temporally controlled manner, as with phototherapy. Recent progress in the field has provided metal complexes that can be triggered to create covalent adducts with nucleic acids both in vitro and in cells. Furthermore, several of these agents have been shown to induce cytotoxicity in cancer cell lines, in vitro tumor models, and in vivo animal models. In the last year, new compounds have been reported that can be activated with low energy light within the therapeutic window, where light penetration through tissue is sufficient to access larger volume tumors. This review highlights the advances that demonstrate the potential of light-activated metal complexes as therapeutics and research tools for biomedical applications.