Synthesis and biological assessment of a Ruthenium(II) cyclopentadienyl complex in breast cancer cells and on the development of zebrafish embryos

Abstract Ruthenium-based complexes currently attract great attention as they hold promise to replace platinum-based drugs as a first line cancer treatment. Whereas ruthenium arene complexes are some of the most studied species for their potential anticancer properties, other types of ruthenium complexes have been overlooked for this purpose. Here, we report the synthesis and characterization of Ru(II) cyclopentadienyl (Cp), Ru(II) cyclooctadienyl (COD) and Ru(III) complexes bearing anastrozole or letrozole ligands, third-generation aromatase inhibitors currently used to treat estrogen receptor-positive (ER+) breast cancer. Among these complexes, Ru(II)Cp 2 was the only species found to be stable in DMSO and in cell culture media and as a result, the only complex for which the in vitro and in vivo biological activities were investigated. Unlike anastrozole alone, complex 2 was considerably cytotoxic in vitro (IC50 values