Targets, Mechanisms and Cytotoxicity of Half-Sandwich Ir(III) Complexes Are Modulated by Structural Modifications on the Benzazole Ancillary Ligand

Pd(II)/1,10-phenanthroline complexes bearing arene ligands: On the role of N- vs O-coordination to tune their cellular activity and binding ability towards DNA and RNA

Three Pd(II)-based complexes of 1,10-phenanthroline and N- or O-coordinating ligands have been synthesised and tested with different relevant biosubstrates like double-stranded DNA, double and triple helix of RNA, DNA G-quadruplexes of different conformations and bovine serum albumin. Here a correlation between N- vs O-coordinating elements and binding mechanism emerged, where the N-coordinating ligands proved to be the most promising. These outcomes were confirmed also in the cellular experiments. The Pd(II) complex with naphthalene-1,8-diamine is the one that is able to be carried by BSA, to strongly bind nucleic acids, to produce reactive oxygen species (ROS) and to show the best cellular performances (poorly toxic towards healthy cells and highly toxic against the cisplatin-resistant cancer cell line). On the opposite, the complex with benzene-1,2-diolate may be sequestered by BSA, weakly binds nucleic acids, does not produce ROS and shows poor cellular activity. The complex with benzene-1,2-diamine stays in between. Other mechanistic details are discussed which show that the biophysical behaviour is the sum of the contribution of aromaticity, charge and N- or O-coordination.

Anticancer iridium(iii) cyclopentadienyl complexes

A comprehensive review of anticancer iridium(iii) cyclopentadienyl complexes, including a critical discussion of structure–activity relationships and mechanisms of action, is provided.

Identification of Cellular Protein Targets of a Half-Sandwich Iridium(III) Complex Reveals Its Dual Mechanism of Action via Both Electrophilic and Oxidative Stresses

Identification of intracellular targets of anticancer drug candidates provides key information on their mechanism of action. Exploiting the ability of the anticancer (C∧N)-chelated half-sandwich iridium(III) complexes to covalently bind proteins, click chemistry with a bioorthogonal azido probe was used to localize a phenyloxazoline-chelated iridium complex within cells and profile its interactome at the proteome-wide scale. Proteins involved in protein folding and actin cytoskeleton regulation were identified as high-affinity targets. Upon iridium complex treatment, the folding activity of Heat Shock Protein HSP90 was inhibited in vitro and major cytoskeleton disorganization was observed. A wide array of imaging and biochemical methods validated selected targets and provided a multiscale overview of the effects of this complex on live human cells. We demonstrate that it behaves as a dual agent, inducing both electrophilic and oxidative stresses in cells that account for its cytotoxicity. The proposed methodological workflow can open innovative avenues in metallodrug discovery.

Development of a Highly In Vivo Efficacious Dual Antitumor and Antiangiogenic Organoiridium Complex as a Potential Anti-Lung Cancer Agent

While the phenomenal clinical success of blockbuster platinum (Pt) drugs is highly encouraging, the inherent and acquired resistance and dose-limiting side effects severely limit their clinical application. To find a better alternative with translational potential, we synthesized a library of six organo-IrIII half-sandwich [(η5-CpX)Ir(N∧N)Cl]+-type complexes. In vitro screening identified two lead candidates [(η5-CpXPh)Ir(Ph2Phen)Cl]+ (5, CpXPh = tetramethyl-phenyl-cyclopentadienyl and Ph2Phen = 4,7-diphenyl-1,10-phenanthroline) and [(η5-CpXBiPh)Ir(Ph2Phen)Cl]+ (6, CpXBiPh = tetramethyl-biphenyl-cyclopentadienyl) with nanomolar IC50 values. Both 5 and 6 efficiently overcame Pt resistance and presented excellent cancer cell selectivity in vitro. Potent antiangiogenic properties of 6 were demonstrated in the zebrafish model. Satisfyingly, 6 and its nanoliposome Lipo-6 presented considerably higher in vivo antitumor efficacy as compared to cisplatin, as well as earlier reported IrIII half-sandwich complexes in mice bearing the A549 non-small lung cancer xenograft. In particular, complex 6 is the first example of this class that exerted dual in vivo antiangiogenic and antitumor properties.

Novel valproate half-sandwich rhodium and iridium conjugates to fight against multidrug-resistant Gram-positive bacteria

New valproate Ir(III) and Rh(III) half-sandwich conjugates containing a C,N-phenylbenzimidazole chelated ligand have been synthesized and characterized. The valproic acid conjugation to organometallic fragments seems to switch on the antibacterial activity of the complexes towards Enterococcus faecium and Staphylococcus aureus Gram-positive bacteria.