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Substitution of a labile Cl− for an NHC ligand in DNA-intercalating [Pt(terpyridine)]+ complexes improved the cytotoxicity and cellular accumulation, while in vivo studies indicated good tolerability in zebrafish.

The substitution of phenyl rings in established drugs with ferrocenyl moieties has been reported to yield compounds with improved biological activity and alternative modes of action, often involving the formation of reactive oxygen species (ROS). Translating this concept to N-heterocyclic carbene (NHC) complexes, we report here organometallics with a piano-stool structure that feature di- or tridentate ligand systems. The ligands impacted the cytotoxic activity of the NHC complexes, but the coordination modes seemed to have a limited influence, which may be related to the propensity of forming the same species in solution. In general, the stability of the complexes in an aqueous environment and their reactivity to selected biomolecules were largely dominated by the nature of the metal center. While the complexes promoted the formation of ROS, the levels did not correlate with their cytotoxic activity. However, the introduction of ferrocenyl moieties had a significant impact on the antiproliferative potency of the complexes and, in particular, some of the ferrocenyl-functionalized compounds yielded IC

A new [PdPtL4]4+ heterobimetallic cage containing hydrazone linkages has been synthesised using the sub-component self-assembly approach.

The incorporation of the ferrocenyl moiety into a bioactive molecule may significantly alter the activity of the resulting conjugate. By applying this strategy, we designed ferrocenyl analogs of monastrol - the first low molecular weight kinesin spindle protein (KSP) inhibitor. The obtained compounds showed low micromolar antiproliferative activity towards a panel of sensitive and ABC-overexpressing cancer cells. Most cytotoxic compounds exhibited also higher KSP modulatory activity and ability for ROS generation compared to monastrol. The increased bioactivity of the studied compounds can be attributed to the presence of the ferrocenyl group.

Understanding binding site preferences in biological systems as well as affinities to binding partners is a crucial aspect in metallodrug development. We here present a mass spectrometry-based method to compare relative stabilities of metal-peptide adducts in the gas phase. Angiotensin 1 and substance P were used as model peptides. Incubation with isostructural N-heterocyclic carbene (NHC) complexes of RuII , OsII , RhIII , and IrIII led to the formation of various adducts, which were subsequently studied by energy-resolved fragmentation experiments. The gas-phase stability of the metal-peptide bonds depended on the metal and the binding partner. Of the four complexes used, the OsII derivative bound strongest to Met, while RuII formed the most stable coordination bond with His. RhIII was identified as the weakest peptide binder and IrIII formed peptide adducts with intermediate stability. Probing these intrinsic gas-phase properties can help in the interpretation of biological activities and the design of site-specific protein binding metal complexes.

N-Heterocyclic carbene (NHC) ligands are widely investigated in medicinal inorganic chemistry. Here, we report the preparation and characterization of a series of half-sandwich [M(L)(NHC)Cl2] (M = Ru, Os, Rh, Ir; L = cym/Cp*) complexes with a N-flanking anthracenyl moiety attached to imidazole- and benzimidazole-derived NHC ligands. The anticancer activity of the complexes was investigated in cell culture studies where, in comparison to a Rh derivative with an all-carbon-donor-atom-based ligand (5a), they were found to be cytotoxic with IC50 values in the low micromolar range. The Ru derivative 1a was chosen as a representative for stability studies as well as for biomolecule interaction experiments. It underwent partial chlorido/aqua ligand exchange in DMSO-d6/D2O to rapidly form an equilibrium in aqueous media. The reactions of 1a with biomolecules proceeded quickly and resulted in the formation of adducts with amino acids, DNA, and protein. Hen egg white lysozyme crystals were soaked with 1a, and the crystallographic analysis revealed an interaction with an l-aspartic acid residue (Asp119), resulting in the cleavage of the p-cymene ligand but the retention of the NHC moiety. Cell morphology studies for the Rh analog 3a suggested that the cytotoxicity is exerted via mechanisms different from that of cisplatin.

We report investigations on the anticancer activity of organometallic [MII/III (η6 -p-cymene/η5 -pentamethylcyclopentadienyl)] (M=Ru, Os, Rh, and Ir) complexes of N-heterocyclic carbenes (NHCs) substituted with a triazolyl moiety. Depending on the precursors, the NHC ligands displayed either mono- or bidentate coordination via the NHC carbon atom or as N,C-donors. The metal complexes were investigated for their stability in aqueous solution, with the interpretation supported by density functional theory calculations, and reactivity to biomolecules. In vitro cytotoxicity studies suggested that the nature of both the metal center and the lipophilicity of the ligand determine the biological properties of this class of compounds. The IrIII complex 5 d bearing a benzimidazole-derived ligand was the most cytotoxic with an IC50 value of 10 μM against NCI-H460 non-small cell lung carcinoma cells. Cell uptake and distribution studies using X-ray fluorescence microscopy revealed localization of 5 d in the cytoplasm of cancer cells.

Metal complexes can be considered a "paradigm of promiscuity" when it comes to their interactions with proteins. They often form adducts with a variety of donor atoms in an unselective manner. We have characterized the adducts formed between a series of isostructural N-heterocyclic carbene (NHC) complexes with Ru, Os, Rh, and Ir centers and the model protein hen egg white lysozyme by X-ray crystallography and mass spectrometry. Distinctive behavior for the metal compounds was observed with the more labile Ru and Rh complexes targeting mainly a surface l-histidine moiety through cleavage of p-cymene or NHC co-ligands, respectively. In contrast, the more inert Os and Ir derivatives were detected abundantly in an electronegative binding pocket after undergoing ligand exchange of a chlorido ligand for an amino acid side chain. Computational studies supported the binding profiles and hinted at the role of the protein microenvironment for metal complexes eliciting selectivity for specific binding sites on the protein.

A strategy is presented that enables the quantitative assembly of a heterobimetallic [PdPtL4 ]4+ cage. The presence of two different metal ions (PdII and PtII ) with differing labilities enables the cage to be opened and closed selectively at one end upon treatment with suitable stimuli. Combining an inert PtII tetrapyridylaldehyde complex with a suitably substituted pyridylamine and PdII ions led to the assembly of the cage. 1 H and DOSY NMR spectroscopy and ESI mass spectrometry data were consistent with the quantitative formation of the cage, and the heterobimetallic structure was confirmed using single-crystal X-ray crystallography. The structure of the host-guest adduct with a 2,6-diaminoanthraquinone guest molecule was determined. Addition of N,N'-dimethylaminopyridine (DMAP) resulted in the formation of the open-cage [PtL4 ]2+ compound and [Pd(DMAP)4 ]2+ complex. This process could then be reversed, with the reformation of the cage, upon addition of p-toluenesulfonic acid (TsOH).

N-Heterocyclic carbene (NHC) ligands are widely investigated in medicinal inorganic chemistry. Here, we report the preparation and characterization of a series of half-sandwich [M(L)(NHC)Cl

The stoichiometry and stability constants of the gallium(III) and iron(III) complexes of two alkoxycarbonylmethyl-3-hydroxy-2(1H)-pyridinone ligands were determined by means of pH-potentiometry, UV–Vis spectrophotometry and 1H and 71Ga NMR spectroscopy in aqueous solution. The cytotoxicity of one of the gallium(III) complexes was also measured in multidrug resistant/non-resistant human colon adenocarcinoma cell lines. Iron(III) forms complexes with the studied 3-hydroxy-2-pyridinones of higher stability than gallium(III), while the obtained pFe values are significantly lower (pFe: 14.95, 15.06; pH 7.4, cM = 1 µM, cL = 10 µM) compared to those of typical iron binders such as deferiprone or transferrin. The moderate gallium(III) and iron(III) binding ability of the compounds stands for lower solution complex stability compared to that of analogous bidentate non-substituted 3-hydroxy-2-pyridinone or 3-hydroxy-4-pyridinone (O,O) donor ligands. Tris-ligand complexes of the general formula [ML3] (M = Ga, Fe) predominate at physiological pH for both ligands. No interaction with cell culture medium components was observed in the millimolar concentration range of gallium(III) complexes, however they can suffer significant decomposition at biologically relevant low concentrations leading to negligible cytotoxic activity. The redox potential of the studied iron–3-hydroxy-2-pyridinone complex (E1/2 = −597 mV at pH 7.4) falls into the range that is typical of iron(III) complexes with conventional bidentate (O,O) donor-containing chelators.

In recent years, extensive research efforts have been focused on loading metal complexes onto macromolecular systems such as nanoparticles. We report a ligand with a catechol group based on a picolinamide which allows for coordination to organoruthenium moieties while the catechol group remains available for loading on nanoparticles as delivery vehicles towards tumors. All the compounds were characterized with standard analytical methods and the molecular structure of the ligand 1, and its Ru complexes 1a and 1b were determined by X-ray diffraction analysis. The crystal structure of 1a and 1b showed pseudo-tetrahedral geometry of the Ru center with “piano-stool” conformation and 1 coordinated as an N,O-bidentate ligand, however, the latter depending on the reaction conditions employed. The Ru complexes 1a–1c were effectively loaded on magnetite nanoparticles as characterized by inductively-coupled plasma mass spectrometry (ICP-MS), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR).

Ruthenium-based complexes have attracted attention as promising anticancer candidates due to their lower general toxicity than the widely used platinum drugs. The complex [Ru

Redox-active Cu(II) complexes are able to form reactive oxygen species (ROS) in the presence of oxygen and reducing agents. Recently, Faller et al. reported that ROS generation by Cu(II) ATCUN complexes is not as high as assumed for decades. High complex stability results in silencing of the Cu(II)/Cu(I) redox cycle and therefore leads to low ROS generation. In this work, we demonstrate that an exchange of the ��-amino acid Gly with the ��-amino acid ��-Ala at position 2 (Gly2�����-Ala2) of the ATCUN motif reinstates ROS production (���OH and H2O2). Potentiometry, cyclic voltammetry, EPR spectroscopy and DFT simulations were utilized to explain the increased ROS generation of these ��-Ala2-containing ATCUN complexes. We also observed enhanced oxidative cleavage activity towards plasmid DNA for ��-Ala2 compared to the Gly2 complexes. Modifications with positively charged Lys residues increased the DNA affinity through electrostatic interactions as determined by UV/VIS, fluorescence, and CD spectroscopy, and consequently led to a further increase in nuclease activity. A similar trend was observed regarding the cytotoxic activity of the complexes against several human cancer cell lines where ��-Ala2 peptide complexes had lower IC50 values compared to Gly2. The higher cytotoxicity could be attributed to an increased cellular uptake as determined by ICP-MS measurements.

While most Rh-N-heterocyclic carbene (NHC) complexes currently investigated in anticancer research contain a Rh(III) metal center, an increasing amount of research is focusing on the cytotoxic activity and mode of action of square-planar [RhCl(COD)(NHC)] (where COD = 1,5-cyclooctadiene) which contains a Rh(I) center. The enzyme thioredoxin reductase (TrxR) and the protein albumin have been proposed as potential targets, but the molecular processes taking place upon protein interaction remain elusive. Herein, we report the preparation of peptide-conjugated and its nonconjugated parent [RhCl(COD)(NHC)] complexes, an in-depth investigation of both their stability in solution, and a crystallographic study of protein interaction. The organorhodium compounds showed a rapid loss of the COD ligand and slow loss of the NHC ligand in aqueous solution. These ligand exchange reactions were reflected in studies on the interaction with hen egg white lysozyme (HEWL) as a model protein in single-crystal X-ray crystallographic investigations. Upon treatment of HEWL with an amino acid functionalized [RhCl(COD)(NHC)] complex, two distinct rhodium adducts were found initially after 7 d of incubation at His15 and after 4 weeks also at Lys33. In both cases, the COD and chlorido ligands had been substituted with aqua and/or hydroxido ligands. While the histidine (His) adduct also indicated a loss of the NHC ligand, the lysine (Lys) adduct retained the NHC core derived from the amino acid l-histidine. In either case, an octahedral coordination environment of the metal center indicates oxidation to Rh(III). This investigation gives the first insight on the interaction of Rh(I)(NHC) complexes and proteins at the molecular level.

Proteomics has played an important role in elucidating the fundamental processes occuring in living cells. Translating these methods to metallodrug research (‘metalloproteomics’) has provided a means for molecular target identification of metal-based anticancer agents which should signifcantly advance the research field. In combination with biological assays, these techniques have enabled the mechanisms of action of metallodrugs to be linked to their interactions with molecular targets and aid understanding of their biological properties. Such investigations have profoundly increased our knowledge of the complex and dynamic nature of metallodrug–biomolecule interactions and have provided, at least for some compound types, a more detailed picture on their specific protein-binding patterns. This perspective highlights the progression of metallodrug proteomics research for the identification of non-DNA targets from standard analytical techniques to powerful metallodrug pull-down methods.

Benzoylthiourea derivatives feature several donor atoms capable of coordinating to metal centers. We report here a series of Ru(η6 -p-cymene) complexes employing benzoylthiourea derivatives as ligands. Such ligands often coordinate to metal centers through their S and O donor atoms. We isolated complexes where the ligands were mono- or bidentately coordinated to Ru involving the S donor atom and surprisingly in bidentate coordination mode a deprotonated thiourea nitrogen resulting in a 4-membered ring structure around the metal center. DFT calculations were used to explain the differences in coordination behavior. These were complemented by stability studies and biological investigations of the compounds as anticancer agents. Several of the synthesized derivatives exhibited significant cell growth inhibitory activity, with the complexes featuring bidentate ligands being more potent than their monodentate counterparts. This can be explained by the higher stability of the former under the conditions employed in cell culture assays.

Nonsteroidal antiinflammatory drugs (NSAIDs) have chemopreventive effects in several cancer types, and the oxicam-based NSAIDs meloxicam and piroxicam exhibit potential to treat cancer. We prepared a series of novel oxicams and coordinated them to RuII(cym)Cl and OsII(cym)Cl moieties (η6-p-cymene = cym). The oxicam ligands acted either as monodentate N-donors or bidentate N,O-chelators, depending upon the ligand structure as well as reaction conditions such as the pH value and solvent used in the reaction. The cytotoxic activity of the complexes toward carcinoma cells was investigated. The isoxazolyl motif-containing ligand 1 and its complexes with RuII(cym)Cl 1a and the Os analogue 1b proved to have anticancer activity with IC50 values in a range similar to that observed for the RuIII investigational drug IT-139, and in general the Os compounds were equally or even slightly more potent than the Ru derivatives. Since meloxicam is known as a selective inhibitor of COX-2, molecular docking studies were carr...

The scientific interest in cadmium (Cd) as a human health damaging agent has significantly increased over the past decades. However, particularly the histological distribution of Cd in human tissues is still scarcely defined. Using inductively coupled plasma-mass spectrometry (ICP-MS), we determined the concentration of Cd in 40 different human tissues of four body donors and provided spatial information by elemental imaging on the microscopic distribution of Cd in 8 selected tissues by laser ablation (LA)-ICP-MS. ICP-MS results show that Cd concentrations differ by a factor of 20 000 between different tissues. Apart from the well know deposits in kidney, bone, and liver, our study provides evidence that muscle and adipose tissue are underestimated Cd pools. For the first time, we present spatially resolved Cd distributions in a broad panel of human soft tissues. The defined histological structures are mirrored by sharp cut differences in Cd concentrations between neighboring tissue types, particularly in the rectum, testis, and kidneys. The spatial resolution of the Cd distribution at microscopic level visualized intratissue hot spots of Cd accumulation and is suggested as a powerful tool to elucidate metal based toxicity at histological level.

Redox-modulating anticancer drugs allow the exploitation of altered redox biology observed in many cancer cells. We discovered dinuclear RhIII(Cp*) and IrIII(Cp*) complexes that have in vitro anticancer activity superior to cisplatin and the investigational drug IT-139, while being less toxic in haemolysis and in vivo zebrafish models. The mode of action appears to be related to DNA damage and ROS-mediated stress pathways.

International audience; The promise of the metal(arene) structure as an anticancer pharmacophore has prompted intensive exploration of this chemical space. While N-heterocyclic carbene (NHC) ligands are widely used in catalysis, they have only recently been considered in metal complexes for medicinal applications. Surprisingly, a comparatively small number of studies have been reported in which the NHC ligand was coordinated to the RuII(arene) pharmacophore and even less with an OsII(arene) pharmacophore. Here, we present a systematic study in which we compared symmetrically substituted methyl and benzyl derivatives with the nonsymmetric methyl/benzyl analogues. Through variation of the metal center and the halido ligands, an in-depth study was conducted on ligand exchange properties of these complexes and their biomolecule binding, noting in particular the stability of the M-CNHC bond. In addition, we demonstrated the ability of the complexes to inhibit the selenoenzyme thioredoxin reductase (TrxR), suggested as an important target for anticancer metal-NHC complexes, and their cytotoxicity in human tumor cells. It was found that the most potent TrxR inhibitor diiodido(1,3-dibenzylbenzimidazol-2-ylidene)(η6-p-cymene)ruthenium(II) 1bI was also the most cytotoxic compound of the series, with the antiproliferative effects in general in the low to middle micromolar range. However, since there was no clear correlation between TrxR inhibition and antiproliferative potency across the compounds, TrxR inhibition is unlikely to be the main mode of action for the compound type and other target interactions must be considered in future.

Chalcones and 1,2-benzothiazines are two important classes of bioactive compounds, each scaffold endowed with diverse pharmacological activities. Combining both of these pharmacophores in a single molecule was aimed to yield multi-modal agents. Herein, we report a series of hybrid compounds 3a–3o derived from chalcones and 1,2-benzothiazine cores. They were synthesized from commercially available sodium saccharin, and the resulting 1,2-benzothiazine-derived ketone was then condensed with aromatic aldehydes in an aldol condensation to obtain the respective chalcones. The compounds were characterized using different analytical techniques including FT-IR, NMR spectroscopy, mass spectrometry and X-ray crystallography. Some synthesized chalcones revealed potent and/or selective inhibitory properties towards alkaline phosphatase isozymes transiently expressed in COS-7 cells. A detailed structure-activity and selectivity study was carried out with regard to the effect of different substituents at ortho-, meta- and para-positions of the phenyl residue. Compound 3c was the most effective human intestinal alkaline phosphatase (h-IAP) inhibitor (IC50 value of 1.04 μM), while it was not active against human tissue non-specific alkaline phosphatase (h-TNAP) isozyme. In contrast, 3i was a selective inhibitor of h-TNAP with IC50 values of 0.25 ± 0.01 μM. The possible binding interactions of the most effective inhibitors of h-TNAP and h-IAP were obtained from molecular docking studies.

The development of more potent metal-based drugs relies heavily on the understanding of their behavior in biological environments. Although the specific physicochemical properties of metal ions and their coordination compounds allow the application of element-specific techniques to track their fate after administration to a living organism, the ease of ligand exchanges makes speciation and target identification a challenge. In this review, we discuss selected examples of novel analytical metallomics methods utilizing mass spectrometric detectors often hyphenated with separation systems, and their application to anticancer metallodrug research. An emphasis is put on how these techniques help research to advance in this important scientific area with the ultimate ambition of introducing new anticancer agents into clinical development and use.

RuII(η6-arene) compounds carrying bioactive flavonol ligands have shown promising anticancer activity against tumor cells via a multitargeting mode of action, i.e., through interaction with DNA and inhibition of topoisomerase IIα. By introducing a novel arene ligand based on the amino acid l-phenylalanine (Phe), we aimed to alter the pharmacological properties of the complexes. We report here a series of novel RuII(η6-arene)Cl complexes with different substituents on the phenyl ring of the flavonol which should maintain the multitargeting capability of the parent η6-p-cymene (cym) complexes. Studies with selected examples revealed stability in aqueous solution after quickly forming aqua complexes but rapid decomposition in pure DMSO. The reactions with protein and DNA models proceeded quickly and resulted in cleavage of the flavonol or adduct formation, respectively. The compounds were found to be cytotoxic with significant antiproliferative activity in cancer cells with IC50 values in the low μM range, w...

Anticancer-active RuII -η6 -p-cymene complexes of bioactive 2-pyridinecarbothioamide ligands have been shown to have high selectivity for plectin and can be administered orally. Reported herein is the functionalization of a 2-pyridinecarbothioamide with a sulfonamide group and its conversion into M-η6 -p-cymene complexes (M = Ru, Os). The presence of a sulfonamide moiety in many organic drugs and metal complexes endows these agents with interesting biological properties and can transform the latter into multi-targeted agents. The compounds were characterized with standard methods and the in vitro anticancer activity data was compared with studies on the hydrolytic stability of the complexes and their reactivity to small biomolecules. A molecular modeling study revealed plausible modes of binding of the complexes in the catalytic pocket of carbonic anhydrase II.

Organoruthenium compounds have been widely investigated for their anticancer activity. Here we use one of the classic ligand classes found in organometallics, i.e., N-heterocyclic carbenes (NHC), and coordinate them to the Ru(η6-p-cymene) scaffold as N,C-bidentate ligands substituted with a pyridyl moiety. Introduction of different substituents gave compounds with a wide variety of properties. We investigated their stability in solution and in the presence of biomolecules, in vitro anticancer activity, and cellular uptake to rationalize their biological properties in dependence on the structure. A clear effect of their structure on the stability in water and DMSO was found for some derivatives, which was reflected in the reactivity to biomolecules that was determined with selected representatives of the compound classes. The antiproliferative activity of the compounds was widely dependent on the lipophilicity of the N,C-bidentate ligand, but as cellular accumulation studies revealed, lipophilicity does no...

The reaction of the para-quinone 6,7-dichloroquinoline-5,8-dione with various transition metal dimers led to the unexpected formation of quinoline-ortho-quinone metal complexes. Systematic variation of the reaction conditions helped identify the solvent as the source of the carbonyl oxygen.

Metal-based anticancer agent development can be improved with advanced metallomics methods that allow for quick and efficient screening of metallodrugs for their metabolites in biological media. Cellular accumulation in in vitro settings is not always correlated with cytotoxicity; and protein binding, particularly with albumin and transferrin, can have an important influence on metallodrug transportation, selectivity, and efficacy. We contrast the time-dependent cellular accumulation of both cisplatin and the pre-clinically investigated RAPTA-C in terms of cell uptake and speciation in culture medium via CE-ICP-MS analysis. Despite RAPTA-C being administered at 40-fold higher dose than cisplatin, owing to its much higher IC50 value, the accumulation over time was only 10-fold higher. An optimised CE-ICP-MS method, through the coating of the capillary to prevent protein-capillary surface interactions, resulted in superior resolution and metal-protein adduct identification. It was then used for extracellular speciation in conjunction with [tris(acetylacetonato)cobalt(iii)] as an internal standard. RAPTA-C was found to be more inert to extracellular reactions than cisplatin which could be used to rationalise the observed cellular uptake patterns. While for cisplatin both transferrin and albumin were identified as the main binding partners, RAPTA-C was found to react nearly exclusively with albumin. Moreover, this behaviour was time-dependent and our results also demonstrate that cancer cells have an influence on metal species distribution in the cell culture medium over time.

Ru(II) and Os(II) complexes of 2-pyridinecarbothioamide ligands were introduced as orally administrable anticancer agents (S.M. Meier, M. Hanif, Z. Adhireksan, V. Pichler, M. Novak, E. Jirkovsky, M.A. Jakupec, V.B. Arion, C.A. Davey, B.K. Keppler, C.G. Hartinger, Chem. Sci., 2013, 4, 1837-1846). In order to identify structure-activity relationships, a series of N-phenyl substituted pyridine-2-carbothiamides (PCAs) were obtained by systematically varying the substituents at the phenyl ring. The PCAs were then converted to their corresponding RuII(η6-p-cymene) complexes and characterized spectroscopically and by X-ray diffraction as well as in terms of stability in water and HCl. The cytotoxic activity of the PCA ligands and their respective organoruthenium compounds was evaluated in a panel of cell lines (HCT116, H460, SiHa and SW480). The lipophilic PCAs 1-4 showed cytotoxicity in the low micromolar range and 6 was the most potent compound of the series with an IC50 value of 1.1μM against HCT116 colon cancer cells. These observations were correlated with calculated octanol/water partition coefficient (clogP) data and quantitative estimated druglikeness. A similar trend as for the PCAs was found in their Ru complexes, where the complexes with more lipophilic ligands proved to be more cytotoxic in all tested cell lines. In general, the PCAs and their organoruthenium derivatives demonstrated excellent drug-likeness and cytotoxicity with IC50 values in the low micromolar range, making them interesting candidates for further development as orally active anticancer agents.

We report here the preparation of 2-hydroxy-4-(picolinamido)benzoic acid and its aspirin analogue 2-acetoxy-4-(picolinamido)benzoic acid. Both ligands were used to synthesize organoruthenium and -osmium complexes. The compounds were characterized by NMR spectroscopy, electrospray ionization mass spectrometry and elemental analysis. The molecular structures of Ru and Os complexes of 2-hydroxy-4-(picolinamido)benzoic acid were determined by single crystal X-ray diffraction analysis. They showed a typical piano-stool configuration and the ligand coordinated as an N,N-bidentate chelator to the metal center. The cytotoxic potential of the selected compounds was evaluated in human colon (HCT116, SW480), non-small cell lung (NCI-H460) and cervical (SiHa) carcinoma cells. Surprisingly none of the compounds exhibited antiproliferative activity given the fact that other metal complexes of aspirin derivatives have shown promising anticancer activity.

Metallorganische Tumortherapeutika werden durch Ligandenaustausch aktiviert, und es wird gemeinhin angenommen, dass die resultierenden aktivierten Spezies geringe Selektivitat fur potenzielle zellulare Ziele zeigen. Durch ein Proteomik-basiertes Ziel-Antwort-Profiling konnte jedoch nachgewiesen werden, dass ein Ruthenium-Aren-Pyridincarbothioamid (Plecstatin) eine unerwartet hohe Selektivitat fur Plectin, ein Strukturprotein und Vernetzer des Zytoskeletts, zeigt, was in einem Plectin-Knock-out-Modell in vitro validiert wurde. In Spharoidkulturen konnte gezeigt werden, dass die gezielten Wechselwirkungen mit Plectin das Potenzial haben, den invasiven Charakter von Tumoren zu inhibieren. Nach oraler Gabe wirkte Plecstatin-1 im invasiven B16-Melanom starker tumorinhibierend als im CT-26-Kolonkarzinom-Tumormodell.

The nitrogen- and sulfur-containing 1,2-benzothiazines meloxicam and piroxicam are widely used as nonsteroidal anti-inflammatory drugs. Intrigued by the presence of multiple donor atoms and therefore potentially rich coordination chemistry, we prepared a series of organometallic Ru and Os compounds with meloxicam and piroxicam featuring either as mono- or bidentate ligand systems. The choice of the solvent and the pH value was identified as the critical parameter to achieve selectively mono- or bidentate coordination. The coordination modes were confirmed experimentally by NMR spectroscopy and single crystal X-ray diffraction analysis. Using DFT calculations, it was established that complexes in which meloxicam acts as a bidentate N,O donor are energetically more favorable than coordination as O,O and S,O donor systems. Since meloxicam and piroxicam derivatives have shown anticancer activity in the past, we aimed to compare the complexes with mono- and bidentate ligands on their in vitro anticancer activity. However, stability studies revealed that only the latter complexes were stable in [D6 ]DMSO/D2 O (5:95) and therefore no direct comparisons could be made. The meloxicam complexes 1 and 2 showed moderate cytotoxicity, whereas the piroxicam derivatives 5 and 6 were hardly active against the utilized cell lines.

Despite the severe side effects and the emergence of drug resistance, the use of DNA-targeting platinum drugs remains strong either alone or in a combination chemotherapy regimen. New strategies and formulations are being explored in the design of anticancer metal complexes that exhibit nonclassical modes of action, selectively hit precise biomolecular targets or are even able to induce immunogenic anticancer activity. These developments will ameliorate the systemic toxicity of metal-based drugs and widen the range of treatable cancers.