Tumour-inhibiting platinum complexes--state of the art and future perspectives

RuIII-Morpholine-Derived Thiosemicarbazone-Based Metallodrugs: Lysosome-Targeted Anticancer Agents

The idea of coordinating biologically active ligand systems to metal centers to exploit their synergistic effects has gained momentum. Therefore, in this report, three RuIII complexes 1-3 of morpholine-derived thiosemicarbazone ligands have been prepared and characterized by spectroscopy and HRMS along with the structure of 2 through a single-crystal X-ray diffraction study. The solution stability of 1-3 was tested using conventional techniques such as UV-vis and HRMS. Further, the anticancer activity of 1-3 was tested in HT-29 and HeLa cancer cell lines. To gain insight into their mechanism of action, the cytotoxicity, hydrophobicity, and the interaction of 1-3 with DNA and HSA were evaluated by different conventional methods such as absorption, fluorescence, and circular dichroism studies. Along with favorable biomolecule interaction, 1-3 revealed potent selectivity toward cancer cells, which is a prerequisite for the generation of an anticancer drug. According to cell viability results, 1 has the highest cytotoxicity among all in the group, against both cells, respectively. Additionally, the fluorescence-active ruthenium complexes selectively target lysosomes, which is evaluated by live-cell imaging. 1-3 disrupt the lysosome membrane potential by generating an excessive amount of reactive oxygen species, which results in an apoptotic mode of cell death.

Natural organic matter (NOM) can increase the uptake fluxes of three critical metals (Ga, La, Pt) in a unicellular green alga

Critical metals such as gallium, lanthanum and platinum are considered essential in a modern economy and for the required energy transition. Their relatively recent and increasing use in new technologies have led to an increase in their environmental mobility. As they reach aquatic systems, these metals can interact with organic ligands and especially Natural Organic Matter (NOM). The formation of organic complexes would be expected to reduce metal bioavailability and uptake by living cells, according to the Biotic Ligand Model (BLM). However, exceptions to this model have been determined for several critical metals in the past. The present work compared internalization kinetics of Ga, La and Pt in the green alga Chlamydomonas reinhardtii in the presence of NOMs from different origins: humic and fulvic acids from Suwannee River as well as NOMs from Ontario (Bannister Lake and Luther Marsh). Complexation was determined using a partial ultrafiltration method allowing for a normalization of data based on speciation to compare all conditions based on the concentration of the metal that was not bound to NOM. While internalization metal fluxes varied greatly from one NOM source to the other, uptake was almost always significantly higher than expected based on metal speciation. Quite often, metal internalization fluxes were even significantly increased in the presence of NOM, for the same total metal exposure concentration. For instance, Pt internalization was twice greater in the presence of Bannister Lake NOM than it was in the absence of NOM. The assumption that such exceptions could be explained by NOM characteristics was contradicted by the variable results from one metal to another. To further explore this phenomenon, internalization mechanisms for these individual metals need to be elucidated. This is a necessary step to accurately estimate the risk posed by the presence of these metals in humic aquatic systems.

Computational and experimental examinations of new antitumor palladium(II) complex: CT-DNA-/BSA-binding, in-silico prediction, DFT perspective, docking, molecular dynamics simulation and ONIOM

Since the design of metal complexes with better biological activities is important, herein a new palladium(II) complex bearing en and acac (en and acac stand for ethylenediamine and acetylacetonato, respectively) as its ligands, [Pd(en)(acac)]NO3 complex, was synthesized and fully characterized. Quantum chemical computations of the palladium(II) complex were done via DFT/B3LYP method. Cytotoxicity activity of the new compound on leukemia cell line (K562) was assessed via MTT method. The findings indicated that the metal complex has remarkable cytotoxic effect than cisplatin. OSIRIS DataWarrior software was employed to calculate in-silico physicochemical and toxicity parameters of the synthesized complex which rendered significant results. To comprehend the interaction type of new metal compound with macromolecules, the in depth investigation of interaction of mentioned complex with CT-DNA and BSA was accomplished by fluorescence, UV-Visible absorption spectroscopy, viscosity measurement, gel electrophoresis, FRET analysis and circular dichroism (CD) spectroscopy. On the other hand, computational molecular docking was carried out and the obtained data demonstrated that H-bond and van der Waals forces are the dominant forces for the binding of the compound to the mentioned biomolecules. Molecular dynamics simulation was also done and confirmed the stability of best docked pose of palladium(II) complex inside DNA or BSA over the time and in presence of water solvent. Also, Our own N-layered Integrated molecular Orbital and molecular Mechanics (ONIOM) methodology based on the hybridization of quantum mechanics and molecular mechanics (QM/MM) methodology was accomplished to inquire about binding of Pd(II) complex with DNA or BSA.HIGHLIGHTSNew biologically active Pd(II) complex was synthesized and characterized.The in silico studies of the designed complex and its ligands were accomplished by OSIRIS DataWarrior softwareInteraction with CT-DNA and BSA was assessed by various spectroscopic methods.Molecular docking simulation supported the interaction with both macromolecules.Based on ONIOM analysis, the structures of the complex and biomolecules are altered after binding. Communicated by Ramaswamy H. Sarma.

Potential cellular targets of platinum in the freshwater microalgae Chlamydomonas reinhardtii and Nitzschia palea revealed by transcriptomics

Platinum group element levels have increased in natural aquatic environments in the last few decades, in particular as a consequence of the use of automobile catalytic converters on a global scale. Concentrations of Pt over tens of μg L-1 have been observed in rivers and effluents. This raises questions regarding its possible impacts on aquatic ecosystems, as Pt natural background concentrations are extremely low to undetectable. Primary producers, such as microalgae, are of great ecological importance, as they are at the base of the food web. The purpose of this work was to better understand the impact of Pt on a cellular level for freshwater unicellular algae. Two species with different characteristics, a green alga C. reinhardtii and a diatom N. palea, were studied. The bioaccumulation of Pt as well as its effect on growth were quantified. Moreover, the induction or repression factors of 16 specific genes were determined and allowed for the determination of possible intracellular effects and pathways of Pt. Both species seemed to be experiencing copper deficiency as suggested by inductions of genes linked to copper transporters. This is an indication that Pt might be internalized through the Cu(I) metabolic pathway. Moreover, Pt could possibly be excreted using an efflux pump. Other highlights include a concentration-dependent negative impact of Pt on mitochondrial metabolism for C. reinhardtii which is not observed for N. palea. These findings allowed for a better understanding of some of the possible impacts of Pt on freshwater primary producers, and also lay the foundations for the investigation of pathways for Pt entry at the base of the aquatic food web.

A Comparison of In Vitro Studies between Cobalt(III) and Copper(II) Complexes with Thiosemicarbazone Ligands to Treat Triple Negative Breast Cancer

Metal complexes have gained significant attention as potential anti-cancer agents. The anti-cancer activity of [Co(phen)2(MeATSC)](NO3)3•1.5H2O•C2H5OH 1 (where phen = 1,10-phenanthroline and MeATSC = 9-anthraldehyde-N(4)-methylthiosemicarbazone) and [Cu(acetylethTSC)Cl]Cl•0.25C2H5OH 2 (where acetylethTSC = (E)-N-ethyl-2-[1-(thiazol-2-yl)ethylidene]hydrazinecarbothioamide) was investigated by analyzing DNA cleavage activity. The cytotoxic effect was analyzed using CCK-8 viability assay. The activities of caspase 3/7, 9, and 1, reactive oxygen species (ROS) production, cell cycle arrest, and mitochondrial function were further analyzed to study the cell death mechanisms. Complex 2 induced a significant increase in nicked DNA. The IC50 values of complex 1 were 17.59 μM and 61.26 μM in cancer and non-cancer cells, respectively. The IC50 values of complex 2 were 5.63 and 12.19 μM for cancer and non-cancer cells, respectively. Complex 1 induced an increase in ROS levels, mitochondrial dysfunction, and activated caspases 3/7, 9, and 1, which indicated the induction of intrinsic apoptotic pathway and pyroptosis. Complex 2 induced cell cycle arrest in the S phase, ROS generation, and caspase 3/7 activation. Thus, complex 1 induced cell death in the breast cancer cell line via activation of oxidative stress which induced apoptosis and pyroptosis while complex 2 induced cell cycle arrest through the induction of DNA cleavage.

A review on metal complexes and its anti-cancer activities: Recent updates from in vivo studies

Research into cancer therapeutics has uncovered various potential medications based on metal-containing scaffolds after the discovery and clinical applications of cisplatin as an anti-cancer agent. This has resulted in many metallodrugs that can be put into medical applications. These metallodrugs have a wider variety of functions and mechanisms of action than pure organic molecules. Although platinum-based medicines are very efficient anti-cancer agents, they are often accompanied by significant side effects and toxicity and are limited by resistance. Some of the most studied and developed alternatives to platinum-based anti-cancer medications include metallodrugs based on ruthenium, gold, copper, iridium, and osmium, which showed effectiveness against many cancer cell lines. These metal-based medicines represent an exciting new category of potential cancer treatments and sparked a renewed interest in the search for effective anti-cancer therapies. Despite the widespread development of metal complexes touted as powerful and promising in vitro anti-cancer therapeutics, only a small percentage of these compounds have shown their worth in vivo models. Metallodrugs, which are more effective and less toxic than platinum-based drugs and can treat drug-resistant cancer cells, are the focus of this review. Here, we highlighted some of the most recently developed Pt, Ru, Au, Cu, Ir, and Os complexes that have shown significant in vivo antitumor properties between 2017 and 2023.

Synthesis of a Novel Gold(I) Complex and Evaluation of Its Anticancer Properties in Breast Cancer Cells

BACKGROUND

Platinum complexes are commonly used for cancer chemotherapy; however, they are not only highly-priced but also have various side effects. It is, therefore, important to design affordable anticancer drugs with minimal side effects.

METHODS

We synthesized a new gold(I) complex, PF6{(BDPEA)(TPPMS) digold(I)} (abbreviated as PBTDG) and tested its cytotoxicity in MCF-7 breast cancer cells. We also evaluated the effects of PBTDG on mitochondrial membrane potential, generation of reactive oxygen species (ROS) and apoptosis in breast cancer cells.

RESULTS

The IC50 values for PBTDG and sorafenib were found to be 1.48 μM and 4.45 μM, respectively. Exposure to PBTDG caused significant and concentration-dependent depletion of ATP and disruption of mitochondrial membrane potential. PBTDG induced 2.6, 3.6, and 5.7-fold apoptosis for 1 μM, 3 μM, and 10 μM concentrations, respectively. The induction of apoptosis by the same concentrations of sorafenib was 1.2, 1.3, and 1.6-fold, respectively. The low concentration of PBTDG (1 μM) induced the generation of ROS by 99.83%, which was significantly higher than the ROS generation caused by the same concentration of sorafenib (73.76%). The ROS induction caused by higher concentrations (5 μM) of PBTDG and sorafenib were 104.95% and 122.11%, respectively.

CONCLUSION

The lower concentration of PBTDG produced similar cytotoxicity and apoptotic effects that were caused by a comparatively higher concentration of known anticancer drug (sorafenib). The anticancer effects of PBTDG are attributed to its tendency to disrupt mitochondrial membrane potential, induction of apoptosis and generation of ROS. Further studies are warranted to test the anticancer effects of PBTDG in animal models of cancer.

A Comprehensive Review on the Development of Titanium Complexes as Cytotoxic Agents

After the discovery of cis-platin, the first metal-based anticancer drugs, budotitane, and titanocene dichloride entered clinical trials. These two classes of complexes were effective against those cell lines that are resistant to cis-platin and other platinum-based drugs. However, the main limitation of these complexes is their low hydrolytic stability. After these two classes, a third generation titanium based complex, i.e. diaminebis(phenolato)bis(alkoxo) titanium(IV), was invented, which showed more hydrolytic stability and high cytotoxicity than budotitane and titanocene dichloride. The Hydrolytic stability of complexes plays an important role in cytotoxicity. Earlier research showed that hydrolytically less stable complexes decompose rapidly into non-bioavailable moiety and become inactive. The mechanism of Ti(IV) complexes of diaminebis(phenolato) bis(alkoxo) is under investigation and is presumed to involve Endoplasmic Reticulum (ER) stress, which leads to apoptosis. The proposed mechanism involves the removal of ligands from the titanium complex and the binding of the Ti center to transferrin protein and its release inside the cell. Also, the structure of the ligand plays a key role in the cytotoxicity of complexes; as the bulkiness of the ligand increased, the cytotoxic nature of complexes decreased.

Synthesis, characterisation and biological evaluation of monometallic Re(I) and heterobimetallic Re(I)/Fe(II) complexes with a 1,2,3-triazolyl pyridine chelating moiety

Bioorganometallic complexes have attracted considerable interest and have shown promise for potential application in the treatment and diagnosis of cancer, as well as bioimaging agents, some acting as theranostic agents. The series of novel ferrocene, benzimidazo[1,2-a]quinoline and fluorescein derivatives with bidentate pyridyl-1,2,3-triazole and 2,2'-dipyridylamine and their tricarbonylrhenium(I) complexes was prepared and fully characterised by NMR, single-crystal X-ray diffraction, UV-Vis and fluorescence spectroscopy in biorelevant conditions. The fluorescein and benzimidazo[1,2-a]quinoline ligands and their complexes with Re(I) showed interactions with ds-DNA/RNA and HSA, characterised by thermal denaturation measurements, fluorimetric and circular dichroism titrations. The binding constants revealed that addition of Re(I) increases the affinity of fluorescein but decreases the affinity of benzimidazo[1,2-a]quinoline. The complexation of Re(I) had the opposite effect on fluorescein and benzimidazo[1,2-a]quinoline ligands' fluorimetric sensitivity upon biomacromolecule binding, Re(I) fluorescein complex emission being strongly quenched by DNA/RNA or HSA, while emission of Re(I) benzimidazo[1,2-a]quinolone complex was enhanced, particularly for HSA, making it a promising fluorescent probe. Some mono- and heterobimetallic complexes showed considerable antiproliferative activity on colon cancer cells (CT26 and HT29), with ferrocene dipyridylamine complexes exhibiting the best inhibitory activity, comparable to cisplatin. The correlation of the cytotoxicity data with the linker type between the ferrocene and the 1,2,3-triazole ring suggests that direct binding of the metallocene to the 1,2,3-triazole is favourable for antitumor activity. The Re(I) benzimidazo[1,2-a]quinolone complex showed moderate antiproliferative activity, in contrast to the Re(I) fluorescein complex, which exhibited weak activity on CT26 cells and no activity on HT29 cells. The accumulation of the Re(I) benzimidazo[1,2-a]quinolone complex in the lysosomes of CT26 cells indicates the site of its bioactivity, thus making this complex a potential theranostic agent.

Equilibrium Studies on Pd(II)-Amine Complexes with Bio-Relevant Ligands in Reference to Their Antitumor Activity

This review article presents an overview of the equilibrium studies on Pd-amine complexes with bio-relevant ligands in reference to their antitumor activity. Pd(II) complexes with amines of different functional groups, were synthesized and characterized in many studies. The complex formation equilibria of Pd(amine)²⁺ complexes with amino acids, peptides, dicarboxylic acids and DNA constituents, were extensively investigated. Such systems may be considered as one of the models for the possible reactions occurring with antitumor drugs in biological systems. The stability of the formed complexes depends on the structural parameters of the amines and the bio-relevant ligands. The evaluated speciation curves can help to provide a pictorial presentation of the reactions in solutions of different pH values. The stability data of complexes with sulfur donor ligands compared with those of DNA constituents, can reveal information regarding the deactivation caused by sulfur donors. The formation equilibria of binuclear complexes of Pd(II) with DNA constituents was investigated to support the biological significance of this class of complexes. Most of the Pd(amine)²⁺ complexes investigated were studied in a low dielectric constant medium, resembling that of a biological medium. Investigations of the thermodynamic parameters reveal that the formation of the Pd(amine)²⁺ complex species is exothermic.

Exploring heterometallic bridged Pt(II)-Zn(II) complexes as potential antitumor agents

The four novel complexes [{cis-PtCl(NH₃)₂(μ-4,4'-bipyridyl)ZnCl(terpy)}](ClO₄)₂ (C1), [{trans-PtCl(NH₃)₂(μ-4,4'-bipyridyl)ZnCl(terpy)}](ClO₄)₂ (C2), [{cis-PtCl(NH₃)₂(μ-pyrazine)ZnCl(terpy)}](ClO₄)₂ (C3) and [{trans-PtCl(NH₃)₂(μ-pyrazine)ZnCl(terpy)}](ClO₄)₂ (C4) (where terpy = 2,2':6',2''-terpyridine) were synthesized and characterized. Acid-base titrations and concentration dependent kinetic measurements for the reactions with biologically relevant ligands such as guanosine-5'-monophosphate (5'-GMP), inosine-5'-monophosphate (5'-IMP) and glutathione (GSH), were studied at pH 7.4 and 37 °C. The binding of the heterometallic bridged cis- or trans-Pt(II)-Zn(II) complexes to calf thymus DNA (CT-DNA) was studied by UV absorption and fluorescence emission spectroscopy and molecular docking. The results indicated that the complexes bind strongly to DNA, through groove binding, hydrogen bonds, and hydrophobic or electrostatic interaction. The possible in vitro DNA protective effect of cis- and trans-Pt-L-Zn complexes has shown that C3 had significant dose-dependent DNA-protective effect and the same ability to inhibit peroxyl as well as hydroxyl radicals. Antiproliferative effect of the complexes, mRNA expression of apoptosis and repair-related genes after treatment in cancer cells indicated that newly synthesized C2 exhibited highly selective cytotoxicity toward colon carcinoma HCT116 cells. Only treatment with trans analog C2 induced effect similar to the typical DNA damaging agent such as cisplatin, characterized by p53 mediated cell response, cell cycle arrest and certain induction of apoptotic related genes. Both cis- and trans-isomers C1 and C2 showed potency to elicit expression of PARP1 mRNA and in vitro DNA binding.

Micellar Form of a Ferrocene-Containing Camphor Sulfonamide with Improved Aqueous Solubility and Tumor Curing Potential

The discovery of new anticancer drugs with а higher, more specific activity and diminished side effects than the conventional chemotherapeutic agents is a tremendous challenge to contemporary medical research and development. To achieve a pronounced efficacy, the design of antitumor agents can combine various biologically active subunits in one molecule, which can affect different regulatory pathways in cancer cells. We recently demonstrated that a newly synthesized organometallic compound, a ferrocene-containing camphor sulfonamide (DK164), possesses promising antiproliferative activity against breast and lung cancer cells. However, it still encounters the problem of solubility in biological fluids. In this work, we describe a novel micellar form of DK164 with significantly improved solubility in aqueous medium. DK164 was embedded in biodegradable micelles based on a poly(ethylene oxide)-b-poly(α-cinnamyl-ε-caprolactone-co-ε-caprolactone)-b-poly(ethylene oxide) triblock copolymer (PEO113-b-P(CyCL3-co-CL46)-b-PEO113), and the physicochemical parameters (size, size distribution, zeta potential, encapsulation efficiency) and biological activity of the obtained system were studied. We used cytotoxicity assays and flow cytometry to determine the type of cell death, as well as immunocytochemistry to assess the influence of the encapsulated drug on the dynamics of cellular key proteins (p53 and NFkB) and the process of autophagy. According to our results, the micellar form of the organometallic ferrocene derivate (DK164-NP) exhibited several advantages compared to the free substance, such as higher metabolic stability, better cellular uptake, improved bioavailability, and long-term activity, maintaining nearly the same biological activity and anticancer properties of the drug.

Probing the interaction of new and biologically active Pd(II) complex with DNA/BSA via joint experimental and computational studies along with thermodynamic, NLO, FMO and NBO analysis

Treatment with transition metal complexes is an efficient method to fight with cancer. Therefore, a new transition metal complex formulated as [Pd(1, 3-pn)(acac)]Cl (pn and acac stand for propylendiamine and acetylacetonate, respectively) was synthesized and analyzed using ¹H NMR, Fourier transform infrared, electronic absorption spectroscopy techniques as well as elemental analysis and conductivity measurement. The geometry optimization, frontier molecular orbital (FMO) analysis, molecular electrostatic potential (MEP), natural bond orbital (NBO) analysis and nonlinear optical (NLO) property were accomplished by density functional theory (DFT) at B3LYP level with 6-311G(d,p)/aug-cc-pVTZ-PP basis set. Preliminary determination of antitumor activity and lipophilicity of this metal complex was performed experimentally and the promising results were obtained. This encouraged us to study the interaction and binding mode/modes of this complex with DNA as the primary receptor for the chemotropic drugs and BSA as the transporter protein in the circulatory system. For this reason, the binding of newly made complex was assessed in-vitro under physiological state using experimental and in-silico molecular modeling studies. So, the CT-DNA binding study of this complex was explored using spectrofluorometric as well as spectrophotometric techniques, viscosity and gel electrophoresis experiments. Furthermore, fluorescence, UV-Vis, F[Formula: see text]rster resonance energy transfer and circular dichroism studies were carried out for BSA binding. The experimental and computational interaction studies showed that [Pd(1, 3-pn)(acac)]Cl complex binds to the minor groove of CT-DNA and interacts with BSA by van der Waals forces and hydrogen bond.

Synthesis, characterization, cytotoxicity and DNA/BSA binding of two amino acid palladium(II) complexes derived from alanine and valine

Two novel palladium(II)-amino acid complexes, [Pd(Ala)2]·H2O (PA) and [Pd(Val)2].H2O (PV) (Ala = alanine; Val = valine) were synthesized and characterized through FTIR, UV/Vis, 1H-NMR spectroscopies, CHN analysis, X-ray crystallography and molar conductivity measurement. Furthermore, cytotoxicity of Pd(II) complexes against human leukemia cancer cell line, MOLT4 showed promising cancer cell death (CC50 = 0.71 ± 0.046 µM for PA; CC50 = 0.85 ± 0.063 µM for PV) that were less than cisplatin (1.59 ± 0.25 µM). Moreover, the interaction of both the complexes with DNA and BSA was studied using UV-Vis absorption and emission spectroscopic techniques that demonstrated the bindings occurred via van der Waals forces and hydrogen bond. Furthermore, the fluorescence titration showed that static quenching mechanism plays predominate role in binding process. All results showed that both complexes have more binding tendency to DNA in compared to BSA that can be a significant achievement for further medical purposes as a potential antitumor candidate. Finally, molecular docking simulation was performed for PA and PV complexes with DNA and BSA and demonstrated both complexes bind to the groove of DNA mainly by hydrogen bond and interact with site I of BSA via hydrogen bond as well.

Metal- and metalloid-based compounds to target and reverse cancer multidrug resistance

Drug resistance remains the major cause of cancer treatment failure especially at the late stage of the disease. However, based on their versatile chemistry, metal and metalloid compounds offer the possibility to design fine-tuned drugs to circumvent and even specifically target drug-resistant cancer cells. Based on the paramount importance of platinum drugs in the clinics, two main areas of drug resistance reversal strategies exist: overcoming resistance to platinum drugs as well as multidrug resistance based on ABC efflux pumps. The current review provides an overview of both aspects of drug design and discusses the open questions in the field. The areas of drug resistance covered in this article involve: 1) Altered expression of proteins involved in metal uptake, efflux or intracellular distribution, 2) Enhanced drug efflux via ABC transporters, 3) Altered metabolism in drug-resistant cancer cells, 4) Altered thiol or redox homeostasis, 5) Altered DNA damage recognition and enhanced DNA damage repair, 6) Impaired induction of apoptosis and 7) Altered interaction with the immune system. This review represents the first collection of metal (including platinum, ruthenium, iridium, gold, and copper) and metalloid drugs (e.g. arsenic and selenium) which demonstrated drug resistance reversal activity. A special focus is on compounds characterized by collateral sensitivity of ABC transporter-overexpressing cancer cells. Through this approach, we wish to draw the attention to open research questions in the field. Future investigations are warranted to obtain more insights into the mechanisms of action of the most potent compounds which target specific modalities of drug resistance.

Peganum harmala Alkaloids Self-Assembled Supramolecular Nanocapsules with Enhanced Antioxidant and Cytotoxic Activities

Amphiphilic macrocycles, such as p-sulfonatocalix[6]arenes (p-SC6), have demonstrated great potential in designing synthetic nanovesicles based on self-assembly approaches. These supramolecular nanovesicles are capable of improving the solubility, stability, and biological activity of various drugs. In the present study, the biologically active harmala alkaloid-rich fraction (HARF) was extracted from Peganum harmala L. seeds. Ultraperformance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC/ESI-MS) analysis of HARF revealed 15 alkaloids. The reversed-phase high-performance liquid chromatography (RP-HPLC) analysis revealed three peaks: peganine, harmol, and harmine. The HARF was then encapsulated in p-SC6 nanocapsules employing a thin-film hydration approach. The designed nanocapsules had an average particle size of 264.8 ± 10.6 nm, and a surface charge of -30.3 ± 2.2 mV. They were able to encapsulate 89.3 ± 1.4, 74.4 ± 1.3, and 76.1 ± 1.7% of the three harmala alkaloids; harmine, harmol, and peganine; respectively. The in vitro drug release experiments showed the potential of the designed nanocapsules to release their cargo at a pH of 5.5 (typical of cancerous tissue). The IC₅₀ values of HARF encapsulated in p-SC6 (H/p-SC6 nanocapsules) were 5 and 2.7 μg/mL against ovarian cancer cells (SKOV-3) and breast adenocarcinoma cells (MCF-7), respectively. The prepared nanocapsules were found to be biocompatible when tested on human skin fibroblasts. Additionally, the antioxidant activity of the designed nanocapsules was 5 times that of the free powder fraction; the IC₅₀ of the H/p-SC6 nanocapsules was 30.1 ± 1.3 μg/mL, and that of the HARF was 169.3 ± 7.2 μg/mL. In conclusion, encapsulation of P. harmala alkaloid-rich fraction into self-assembled p-SC6 significantly increases its antioxidant and cytotoxic activities.

Lung cancer chemotherapy using nanoparticles: Enhanced target ability of redox-responsive and pH-sensitive cisplatin prodrug and paclitaxel

Platinum-based combination therapy is more effective and less toxic, but lack of targeting, and is not capable to enrich in the tumor zone. To obstacle these drawbacks, prodrug and nanotechnology strategies have been investigated in this study. GSH-responsive and pH-responsive cisplatin prodrug was synthesized. Cisplatin prodrug and paclitaxel co-loaded nanoparticles: DDP-P/PTX NPs were constructed. The drug release behavior and cytotoxicity of nanoparticles was assessed in vitro. In vivo anticancer efficiency and toxicity were evaluated on lung cancer bearing mice animal model. DDP-P/PTX NPs had a nanoscale size of 112.9 ± 3.5 nm. A reduction and pH triggered drug release with a synergistic tumor cell inhibition ability was observed by DDP-P/PTX NPs. DDP-P/PTX NPs also exhibited high tumor distribution, low systemic toxicity and remarkable antitumor effects in vivo. DDP-P/PTX NPs could be applied as promising anticancer system for the treatment of NSCLC.

Nanoparticle-based drug delivery systems with platinum drugs for overcoming cancer drug resistance

Platinum drugs are commonly used in cancer therapy, but their therapeutic outcomes have been significantly compromised by the drug resistance of cancer cells. To this end, intensive efforts have been made to develop nanoparticle-based drug delivery systems for platinum drugs, due to their multifunctionality in delivering drugs, in modulating the tumor microenvironment, and in integrating additional genes, proteins, and small molecules to overcome chemoresistance in cancers. To facilitate the clinical application of these promising nanoparticle-based platinum drug delivery systems, this paper summarizes the common mechanisms for chemoresistance towards platinum drugs, the advantages of nanoparticles in drug delivery, and recent strategies of nanoparticle-based platinum drug delivery. Furthermore, we discuss how to design delivery platforms more effectively to overcome chemoresistance in cancers, thereby improving the efficacy of platinum-based chemotherapy.

Host-Guest Complexation of Oxaliplatin and Para-Sulfonatocalix[n]Arenes for Potential Use in Cancer Therapy

P-sulfonatocalix[n]arenes have demonstrated a great potential for encapsulation of therapeutic drugs via host-guest complexation to improve solubility, stability, and bioavailability of encapsulated drugs. In this work, guest-host complexes of a third-generation anticancer drug (oxaliplatin) and p-4-sulfocalix[n]arenes (n = 4 and 6; p-SC4 and p-SC6, respectively) were prepared and investigated, using 1H NMR, UV, Job's plot analysis, and DFT calculations, for use as cancer therapeutics. The peak amplitude of the prepared host-guest complexes was linearly proportional to the concentration of oxaliplatin in the range of 1.0 × 10-5 M-1 to 2.1 × 10-4 M-1. The reaction stoichiometry between either p-SC4 or p-SC6 and oxaliplatin in the formed complexes was 1:1. The stability constants for the complexes were 5.07 × 104 M-1 and 6.3 × 104 M-1. These correspond to complexation free energy of -6.39 and -6.52 kcal/mol for p-SC4 and p-SC6, respectively. Complexation between oxaliplatin and p-SC4 or p-SC6 was found to involve hydrogen bonds. Both complexes exhibited enhanced biological and high cytotoxic activities against HT-29 colorectal cells and MCF-7 breast adenocarcinoma compared to free oxaliplatin, which warrants further investigation for cancer therapy.

Experimental and Computational Investigations of Carboplatin Supramolecular Complexes

Supramolecular systems (macromolecules), such as calix[n]arenes (SCn), cyclodextrins (CDs), and cucurbiturils (CBs), are promising vehicles for anticancer drugs. In this work, guest-host complexes of carboplatin, a second-generation platinum-based anticancer drug, and p-4-sulfocalix[n]arenes (n = 4 and 6; PS4 and PS6, respectively) were prepared and studied using ¹H NMR, UV, Job's plot analysis, HPLC, and density-functional theory calculations. The experimental and the computational studies suggest the formation of 1:1 complexes between carboplatin and each of PS4 and PS6. The stability constants of the formed complexes were estimated to be 5.3 × 10⁴ M^-1 and 9.8 × 10⁴ M^-1, which correspond to free energy of complexation of -6.40 and -6.81 kcal mol^-1, in the case of PS4 and PS6, respectively. The interaction free energy depends on the different inclusion modes of carboplatin in the host cavities. UV-vis findings and atoms in molecules analysis showed that hydrogen bond interactions stabilize the host-guest complexes without the full inclusion in the host cavity. The in vitro anticancer study revealed that both complexes exhibited stronger anticancer activities against breast adenocarcinoma cells (MCF-7) and lung cancer cells (A-549) compared to free carboplatin, preluding to their potential use in cancer therapy.

Synthesis, characterization, DNA binding, topoisomerase inhibition, and apoptosis induction studies of a novel cobalt(III) complex with a thiosemicarbazone ligand

In this study, 9-anthraldehyde-N(4)-methylthiosemicarbazone (MeATSC) 1 and [Co(phen)2(O2CO)]Cl·6H2O 2 (where phen = 1,10-phenanthroline) were synthesized. [Co(phen)2(O2CO)]Cl·6H2O 2 was used to produce anhydrous [Co(phen)2(H2O)2](NO3)33. Subsequently, anhydrous [Co(phen)2(H2O)2](NO3)33 was reacted with MeATSC 1 to produce [Co(phen)2(MeATSC)](NO3)3·1.5H2O·C2H5OH 4. The ligand, MeATSC 1 and all complexes were characterized by elemental analysis, FT IR, UV-visible, and multinuclear NMR (1H, 13C, and 59Co) spectroscopy, along with HRMS, and conductivity measurements, where appropriate. Interactions of MeATSC 1 and complex 4 with calf thymus DNA (ctDNA) were investigated by carrying out UV-visible spectrophotometric studies. UV-visible spectrophotometric studies revealed weak interactions between ctDNA and the analytes, MeATSC 1 and complex 4 (Kb = 8.1 × 105 and 1.6 × 104 M-1, respectively). Topoisomerase inhibition assays and cleavage studies proved that complex 4 was an efficient catalytic inhibitor of human topoisomerases I and IIα. Based upon the results obtained from the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay on 4T1-luc metastatic mammary breast cancer cells (IC50 = 34.4 ± 5.2 μM when compared to IC50 = 13.75 ± 1.08 μM for the control, cisplatin), further investigations into the molecular events initiated by exposure to complex 4 were investigated. Studies have shown that complex 4 activated both the apoptotic and autophagic signaling pathways in addition to causing dissipation of the mitochondrial membrane potential (ΔΨm). Furthermore, activation of cysteine-aspartic proteases3 (caspase 3) in a time- and concentration-dependent manner coupled with the ΔΨm, studies implicated the intrinsic apoptotic pathway as the major regulator of cell death mechanism.

Crystal structures of chlorido-[dihy-droxybis-(1-imino-eth-oxy)]arsanido-κ3 N,As,N']platinum(II) and of a polymorph of chlorido-[dihy-droxybis-(1-imino-prop-oxy)arsanido-κ3 N,As,N']platinum(II)

Each central platinum(II) atom in the crystal structures of chlorido-[dihy-droxybis-(1-imino-eth-oxy)arsanido-κ3 N,As,N']platinum(II), [Pt(C4H10AsN2O4)Cl] (1), and of chlorido-[dihy-droxybis-(1-imino-prop-oxy)arsanido-κ3 N,As,N']platinum(II), [Pt(C6H14AsN2O4)Cl] (2), is coordinated by two nitro-gen donor atoms, a chlorido ligand and to arsenic, which, in turn, is coordinated by two oxygen donor ligands, two hydroxyl ligands and the platinum(II) atom. The square-planar and trigonal-bipyramidal coordination environments around platinum and arsenic, respectively, are significantly distorted with the largest outliers being 173.90 (13) and 106.98 (14)° for platinum and arsenic in (1), and 173.20 (14)° and 94.20 (9)° for (2), respectively. One intra-molecular and four classical inter-molecular hydrogen-bonding inter-actions are observed in the crystal structure of (1), which give rise to an infinite three-dimensional network. A similar situation (one intra-molecular and four classical inter-molecular hydrogen-bonding inter-actions) is observed in the crystal structure of (2). Various π-inter-actions are present in (1) between the platinum(II) atom and the centroid of one of the five-membered rings formed by Pt, As, C, N, O with a distance of 3.7225 (7) Å, and between the centroids of five-membered (Pt, As, C, N, O) rings of neighbouring mol-ecules with distances of 3.7456 (4) and 3.7960 (6) Å. Likewise, weak π-inter-actions are observed in (2) between the platinum(II) atom and the centroid of one of the five-membered rings formed by Pt, As, C, N, O with a distance of 3.8213 (2) Å, as well as between the Cl atom and the centroid of a symmetry-related five-membered ring with a distance of 3.8252 (12) Å. Differences between (2) and the reported polymorph [Miodragović et al. (2013 ▸). Angew. Chem. Int. Ed. 52, 10749-10752] are discussed.

Beclin1 affected by DN604 upregulates chemo-sensitivity of cervix SiHa cancer cells via inhibiting CK2-MRN-DSBs repair

DN604, containing a functional dicarboxylato ligand as carboplatin analogue, was significantly studied to explore its potency of antitumour activity. In vitro and in vivo experimental evidence indicated that DN604 exhibited superior antitumor activity than present platinum(II)-based agents in cervix squamous carcinoma SiHa cancer cells. Moreover, DN604 showed negligible toxic effects in vivo as confirmed as Pt accumulation and body weights of mice. Mechanistic studies have shown that DN604 suppressed CK2-mediated MRN complex to improve its antitumor efficacy by promoting DNA double-strand breaks repair. Furthermore, DN604 could inhibit Beclin1 and attenuate CK2-mediated several DSBs repair-related pathways, thus leading to cell apoptosis. Taken together, our research demonstrated that DN604 with the functional dicarboxylato ligand as the leaving group could effectively enhance chemo-sensitivity of SiHa cells to platinum-based agents via suppressing Beclin1 and CK2-mediated MRN-DSBs repair.

Biological properties of metal complexes of curcumin

Curcumin, a naturally occurring phenolic compound isolated from Curcuma longa, has different pharmacological effects, including antiinflammatory, antimicrobial, antioxidant, and anticancer properties. However, curcumin has been found to have a limited bioavailability because of its hydrophobic nature, low-intestinal absorption, and rapid metabolism. Therefore, there is a need for enhancing the bioavailability and its solubility in water in order to increase the pharmacological effects of this bioactive compound. One strategy is curcumin complexation with transition metals to circumvent the abovementioned problems. Curcumin can undergo chelation with various metal ions to form metallo-complexes of curcumin, which may show greater effects as compared with curcumin alone. Promising results with metal curcumin complexes have been observed with regard to antioxidant, anticancer, and antimicrobial activity, as well as in treatment of Alzheimer's disease. The present review provides a concise summary of the characterization and biological properties of curcumin-metal complexes. © 2019 BioFactors, 45(3):304-317, 2019.

Challenges and Chances in the Preclinical to Clinical Translation of Anticancer Metallodrugs

Despite being “sentenced to death” for quite some time, anticancer platinum compounds are still the most frequently prescribed cancer therapies in the oncological routine and recent exciting news from late-stage clinical studies on combinations of metallodrugs with immunotherapies suggest that this situation will not change soon. It is perhaps surprising that relatively simple molecules like cisplatin, discovered over 50 years ago, are still widely used clinically, while none of the highly sophisticated metal compounds developed over the last decade, including complexes with targeting ligands and multifunctional (nano)formulations, have managed to obtain clinical approval. In this book chapter, we summarize the current status of ongoing clinical trials for anticancer metal compounds and discuss the reasons for previous failures, as well as new opportunities for the clinical translation of metal complexes.

Pt(IV) Bifunctional Prodrug Containing 2-(2-Propynyl)octanoato Axial Ligand: Induction of Immunogenic Cell Death on Colon Cancer

The synthesis, characterization, and in vitro activity of a cyclohexane-1 R,2 R-diamine-based Pt(IV) derivative containing the histone deacetylase inhibitor rac-2-(2-propynyl)octanoato, namely, ( OC-6-44)-acetatodichlorido(cyclohexane-1 R,2 R-diamine)( rac-2-(2-propynyl)octanoato)platinum(IV), are reported together with those of its isomers containing enantiomerically enriched axial ligands. These Pt(IV) complexes showed comparable activity, of 2 orders of magnitude higher than reference drug oxaliplatin on three human (HCT 116, SW480, and HT-29) and one mouse (CT26) colon cancer cell lines. In vivo experiments were carried out on immunocompetent BALB/c mice bearing the same syngeneic tumor. The complex ( OC-6-44)-acetatodichlorido(cyclohexane-1 R,2 R-diamine)( rac-2-(2-propynyl)octanoato)platinum(IV) showed higher tumor mass Pt accumulation than oxaliplatin, due to its higher lipophilicity, with negligible nephro- and hepatotoxicities when administered intravenously. A remarkable tumor mass invasion by cytotoxic CD8+ T lymphocytes, following the Pt(IV) treatment, indicated a strong induction of immunogenic cell death.

Synthesis and characterization of cyclohexane-1R,2R-diamine-based Pt(iv) dicarboxylato anticancer prodrugs: their selective activity against human colon cancer cell lines

Three pairs of asymmetric dicarboxylato derivatives based on the cisplatin and oxaliplatin-like skeletons have been synthesized de novo or re-synthesized. The axial ligands consist of one medium-chain fatty acid (MCFA), namely clofibrate (i.e. 2-(p-chlorophenoxy)-2-methylpropionic acid, CA), heptanoate (HA) or octanoate (OA), respectively, and an inactive acetato ligand that imparts acceptable water solubility to such conjugates. Stability tests provided evidence for the partial formation of two hydrolyzed products, corresponding to two monoaqua diastereomers derived from the substitution of an equatorial chlorido ligand with a water molecule. The complexes have been tested on three different colon cancer cell lines having different histological history, and also on the cisplatin-sensitive A2780 ovarian cancer cell line for comparison. This allowed the evaluation not only of the increase in activity on passing from Pt(ii) to Pt(iv) derivatives, but also the selectivity towards colon cancer cells brought about by the cyclohexane-1R,2R-diamine carrier ligand.

Randomized controlled trial of lobaplatin plus etoposide vs. cisplatin plus etoposide as first-line therapy in patients with extensive-stage small cell lung cancer

The majority of previous studies of lobaplatin in small cell lung cancer (SCLC) are small phase I-II studies. The present study aimed to verify the non-inferiority (in terms of efficacy) of lobaplatin plus etoposide (EL) vs. cisplatin plus etoposide (EP) in patients with previously untreated extensive-stage SCLC (ES-SCLC). This phase III non-inferiority randomized clinical trial enrolled patients at 17 sites between September 2010 and May 2013. Patients were randomized to EL (30 mg/m² lobaplatin on day 1 and 100 mg/m² etoposide on days 1-3, for 21-day cycles) or EP (80 mg/m² cisplatin on day 1 and 100 mg/m² etoposide on days 1-3, for 21-day cycles). The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate, disease control rate (DCR), toxicity and quality of life (QoL). A total of 234 patients were randomized to the EL (n=122) and EP (n=112) treatment groups. The median PFS, median OS and DCR were 5.1 vs. 5.3 months (P=0.786), 10.6 vs. 9.7 months (P=0.701) and 85.5 vs. 86.7% (P=0.848) in the EL vs. EP groups, respectively. Patients in the EL group had significantly lower frequencies of nephrotoxicity (2.5 vs. 11.7%; P=0.008), nausea (22.3 vs. 40.5%; P=0.003) and vomiting (14.1 vs. 35.1%; P<0.001) than those in the EP group. Overall, EL was not inferior to EP in terms of PFS and OS. The tolerance and QoL of the EL regimen were better than those of the EP regimen. EL is thus an alternative choice for the first-line treatment of ES-SCLC.

A safe and efficacious Pt(ii) anticancer prodrug: design, synthesis, in vitro efficacy, the role of carrier ligands and in vivo tumour growth inhibition

Diaminocyclohexane-Pt(ii)-phenalenyl complexes (1 and 2) showed an appropriate balance between efficacy and toxicity. Compound 2 showed nearly two-fold higher tumour growth inhibition than oxaliplatin in a murine NSCLC tumour model, when a combined drug development approach was used. The fluorescent properties of phenalenone were utilized to understand the mechanistic details of the drug.

Population pharmacokinetics and individualized lobaplatin regimen for the treatment of Chinese small cell lung cancer in the elderly

BACKGROUND

Lobaplatin (LBP) is a third-generation platinum compound.

MATERIAL AND METHODS

This prospective study was performed in 7 institutions in 2014-2016. Elderly small cell lung cancer (SCLC) patients (≥65 years old) were divided into 2 groups to receive LBP regimens according to endogenous creatinine clearance rate (Ccr). LBP was administered at 30 and 20 mg/m in groups A (Ccr ≥ 80 ml/min) and B (60 ml/min ≤ Ccr < 80 ml/min), respectively. The primary endpoint was plasma LBP concentrations. Secondary endpoints were safety and efficacy parameters, including progression-free survival (PFS) and overall survival (OS).

RESULTS

One-hundred patients were enrolled. Median PFS and OS in groups A and B were 155 vs170 days and 306 vs 272 days, respectively. The rates of grade III/IV AEs in groups A and B were 60.8% (n = 31) and 51.0% (n = 25), respectively. In population pharmacokinetics, the area under the curve (AUC) value for group B was 39% lower than that of group A. With LBP administration based on body surface area (BSA), AUC differences between individuals were small.

CONCLUSION

With Ccr ≥ 60 ml/min, BSA based administration is necessary. Meanwhile, LBP-based regimens are reliable in treating elderly patients with SCLC.

Toxicity study of DE-EDCP as a potential drug for cancer therapy: Toxicity profile of DE-EDCP

It was reported that novel O, O'-diethyl-(S, S)-ethylenediamine- N, N'-di-2-(3-cyclohexyl) propanoate dihydrochloride (DE-EDCP) displayed in vitro antiproliferative activity on several human and mouse cancer cell lines, which was comparable to that of the prototypical anticancer drug cisplatin. In order to reveal its toxicity profile, acute and repeated-dose toxicity studies were performed in Naval Medical Research Institute (NMRI) Han mice. The intravenous LD₅₀ values of DE-EDCP were found to be 95.3 and 101.3 mg/kg body weight in female and male mice, respectively. In the subacute toxicity study, DE-EDCP was administered intravenously at the doses of 15, 25, and 40 mg/kg/day for a period of 28 days. There were no adverse effects on general condition, growth, feed and water consumption, and hematological parameters. There was a significant increase in urea and alanine aminotransferase in female mice and aspartate aminotransferase and alkaline phosphatase in both genders in 40 mg/kg/day dose-treated group. The histopathological changes confined to the liver and kidney, but in other organs were not found. Satellite group revealed that changes in the kidney and liver were less pronounced, suggesting their reversibility. Interactions with DNA could also be of importance for understanding DE-EDCP toxic side effects. Hyperchromic effect obtained with ultraviolet-visible, suggested electrostatic interactions between DE-EDCP and calf thymus DNA. The toxicity testing of DE-EDCP was conducted to predict human outcomes.

Pharmacokinetics of lipid-drug conjugates loaded into liposomes

Drugs that are neither lipophilic nor suitable for encapsulation via remote loading procedures are generally characterized by low entrapment efficiencies and poor retention in liposomes. One approach to circumvent this problem consists in covalently linking a lipid to the drug molecule in order to permit its insertion into the vesicle membrane. The nature of the conjugated lipid and linker, as well as the composition of the liposomal bilayer were found to have a profound impact on the pharmacokinetic properties and biodistribution of the encapsulated drugs as well as on their biological activity. This contribution reviews the past and recent developments on liposomal lipid-drug conjugates, and discusses important issues related to their stability and in vivo performance. It also provides an overview of the data that were generated during the clinical assessment of these formulations. The marketing authorization of the immunomodulating compound mifamurtide in several countries as well as the promising results obtained with the lipid prodrug of mitomycin C suggest that carefully designed liposomal formulations of lipid-drug conjugates is a valid strategy to improve a drug's pharmacokinetic profile and with that its therapeutic index and/or efficacy.

Developing an anticancer copper(II) pro-drug based on the nature of cancer cell and human serum albumin carrier IIA subdomain: mouse model of breast cancer

Human serum albumin (HSA)-based drug delivery systems are promising for improving delivery efficiency, anticancer activity and selectivity of anticancer agents. To rationally guide to design HSA carrier for anticancer metal agent, we built a breast mouse model on developing anti-cancer copper (Cu) pro-drug based on the nature of IIA subdomain of HSA carrier and cancer cells. Thus, we first synthesized a new Cu(II) compound derived from tridentate (E)-N'-(5-bromo-2-hydroxybenzylidene)benzohydrazide Schiff base ligand (HL) containing 2 potential leaving groups [indazole (Ind) and NO3-], namely, [Cu(L)(Ind)NO3]. Structural analysis of the HSA complex showed that Cu(L)(Ind)(NO3) could bind to the hydrophobic pocket of the HSA IIA subdomain. Lys199 and His242 coordinate with Cu2+ by replacing the indazole and NO3 ligands of [Cu(L)(Ind)NO3]. The release behavior of the Cu compound from the HSA complex is different at different pH levels. [Cu(L)(Ind)NO3] can enhance cytotoxicity by 2 times together with HSA specifically in cancer cells but has no such effect on normal cells in vitro. Importantly, our in vivo results showed that the HSA complex displayed increased selectivity and capacity to inhibit tumor growth and was less toxic than [Cu(L)(Ind)NO3] alone.

Liposomes: Clinical Applications and Potential for Image-Guided Drug Delivery

Liposomes have been extensively studied and are used in the treatment of several diseases. Liposomes improve the therapeutic efficacy by enhancing drug absorption while avoiding or minimizing rapid degradation and side effects, prolonging the biological half-life and reducing toxicity. The unique feature of liposomes is that they are biocompatible and biodegradable lipids, and are inert and non-immunogenic. Liposomes can compartmentalize and solubilize both hydrophilic and hydrophobic materials. All these properties of liposomes and their flexibility for surface modification to add targeting moieties make liposomes more attractive candidates for use as drug delivery vehicles. There are many novel liposomal formulations that are in various stages of development, to enhance therapeutic effectiveness of new and established drugs that are in preclinical and clinical trials. Recent developments in multimodality imaging to better diagnose disease and monitor treatments embarked on using liposomes as diagnostic tool. Conjugating liposomes with different labeling probes enables precise localization of these liposomal formulations using various modalities such as PET, SPECT, and MRI. In this review, we will briefly review the clinical applications of liposomal formulation and their potential imaging properties.

Toxic Effects of Metallopharmaceuticals

Discovery of the metallopharmaceutical cisplatin and its use in antitumour therapy has initiated the rational design and screening of metal-based anticancer agents as potential chemotherapeutics. In addition to the achievements of cisplatin and its therapeutic analogues, there are significant drawbacks to its use: resistance and toxicity. Over the past four decades, numerous transition metal complexes have been synthesized and investigated in vitro and in vivo. The most studied metals among these complexes are platinum and ruthenium. The key features of these investigations is to find novel metal complexes that could potentially exert less toxicity and equal or higher antitumour potency and to overcome other pharmacological deficiencies. Ru complexes have a different mode of action than cisplatin does, some of which are under clinical trials for treating metastatic or cisplatin-resistant tumours. This review consists of the current knowledge, published and unpublished, related to the toxicity of metallopharmaceuticals, and special attention is given to platinum [Pt(II) and Pt(IV)] and ruthenium [Ru(II) and Ru(III)] complexes.