A series of organometallic compounds of general formula [(arene)M(PTA)_nX_m]Y (arene = η⁶-C₁₀H₁₄, η-C₅Me₅); M = Ru(II), Os(II), Rh(III) and Ir(III); X = Cl, mPTA; Y = OTf, PF₆) have been screened for their cytotoxicity and ability to inhibit cathepsin B in vitro, in comparison to the antimetastatic compound NAMI-A. The Ru and Os analogues and NAMI-A showed similar enzyme inhibition properties (with IC₅₀ values in the low μM range), whereas the Rh(III) and Ir(III) compounds were inactive. In order to build up a rational for the observed differences, DFT calculations of the metal complexes adducts with N-acetyl-L-cysteine-N′-methylamide, a mimic for the Cys residue in the cathepsin B active site, were performed to provide insights into binding thermodynamics in solution. Initial structure–activity relationships have been defined with the calculated binding energies of the M–S bonds correlating well with the observed inhibition properties of the compounds.

Singly aquated and diaquated species are key intermediates in the mechanism responsible for the antitumor activity of cisplatin. Aqua complexes [PtX(NH₃)₂(H₂O)]⁺ (X = Cl, OH), obtained in water by hydrolysis of cisplatin and of the inactive isomer transplatin, are transferred into the gas-phase by electrospray ionization. The so-formed ions, cis- and trans-[PtX(NH₃)₂(H₂O)]⁺, have been allowed to react with selected ligands, representing platination targets in the biological environment. The reaction kinetics monitored in the gas-phase show consistently higher reactivity for the chloro complexes, [PtCl(NH₃)₂(H₂O)]⁺, with respect to the hydroxo counterparts, [Pt(OH)(NH₃)₂(H₂O)]⁺. The latter species, both cis- and trans-isomers, have been assayed by IRMPD spectroscopy in the NH/OH stretching region and their vibrational and geometric features are compared with the ones pertaining to the already described chloro complexes, cis- and trans-[PtCl(NH₃)₂(H₂O)]⁺.

Owing to the growing hardware capabilities and the enhancing efficacy of computational methodologies, computational chemistry approaches have constantly become more important in the development of novel anticancer metallodrugs. Besides traditional Pt-based drugs, inorganic and organometallic complexes of other transition metals are showing increasing potential in the treatment of cancer. Among them, Au(I)- and Au(III)-based compounds are promising candidates due to the strong affinity of Au(I) cations to cysteine and selenocysteine side chains of the protein residues and to Au(III) complexes being more labile and prone to the reduction to either Au(I) or Au(0) in the physiological milieu. A correct prediction of metal complexes’ properties and of their bonding interactions with potential ligands requires QM computations, usually at the ab initio or DFT level. However, MM, MD, and docking approaches can also give useful information on their binding site on large biomolecular targets, such as proteins or DNA, provided a careful parametrization of the metal force field is employed. In this review, we provide an overview of the recent computational studies of Au(I) and Au(III) antitumor compounds and of their interactions with biomolecular targets, such as sulfur- and selenium-containing enzymes, like glutathione reductases, glutathione peroxidase, glutathione-S-transferase, cysteine protease, thioredoxin reductase and poly (ADP-ribose) polymerase 1.