Azaindoles: Suitable ligands of cytotoxic transition metal complexes.

This minireview is devoted to the complexes of various transition metals, which contain azaindole ring coordinated to the metal centre, and whose cytotoxicity was studied. We decided to overview this interesting group of coordination compounds with the aim to highlight various structural types of complexes depending on the metal centre (i.e., Pt, Pd, Ru, Ir or Au) and type of the used co-ligand(s). The presented complexes are also reviewed in context of their toxicity, selectivity and processes connected with their mechanism of action. Some of complexes were also studied on in vivo models showing promising results comparable with the commonly used anticancer drug cisplatin. It can be deduced from the herein overviewed literature data regarding transition metal complexes containing azaindoles as ligands, that at least a few of them may represent suitable and promising candidates in the field of anticancer therapy. As one of the examples, the cis-[PtI(2Me4Cl-7aza)] complex (2Me4Cl-7aza = 2-methyl-4-chloro-7-azaindole) should be mentioned, which showed considerably higher in vitro cytotoxicity than cisplatin, the ability to overcome both the acquired and natural resistance of human cancer cells in comparison with the biological action of cisplatin, different mechanism of action than cisplatin and comparable in vivo anticancer activity with cisplatin.