A Bis-Chelating O N O ^ / N N ^ Ligand for the Synthesis of Heterobimetallic Platinum(II)/Rhenium(I) Complexes: Tools for the Optimization of a New Class of Platinum(II) Anticancer Agents

Deferasirox Derivatives as Inhibitors of Kallikrein-Related Peptidases Associated to Neurodegenerative Diseases

Kallikrein-related peptidases are a family of serine proteases whose loss of activity regulation has been particularly linked to neurodegenerative diseases. Moreover, iron overload is also a key process in some of these leading pathological conditions, particularly Alzheimer's disease. It is identified for the first time Deferasirox, a well-known FDA-approved iron chelator (DFX) as an initial hit for kallikrein's (KLK) inhibition and proposed here the design and synthesis of a small library of molecules using DFX as chemical scaffold. Resulting subseries of compounds are evaluated against lead central nervous system KLK's, namely, KLK1, KLK6, and KLK8 using targeted pharmacomodulations on DFX. Beyond DFX, several reversible micromolar inhibitors of these KLKs have been identified as hits and are shown to be devoid of any noticeable cytotoxicity toward neural cell lines commonly used in the field of neurodegenerative diseases. Their ability to chelate iron is also assessed in comparison to DFX and preformed iron-compound complexes displayed slightly improved inhibition potency for some derivatives with a KLK-dependent manner. Hence, several DFX derivatives are identified as promising starting points for the development of dual therapeutic agents in the context of neurodegenerative diseases where both deregulated KLK's proteolysis and iron dysregulation are involved.

Synthesis and Biological Evaluation of a New Biphenyl-Based Organogold(III) Complex with In Vitro and In Vivo Anticancer Activity

Despite recent advances in cancer treatment, there is still a need for novel compounds with antineoplastic activity. Among 11 biphenyl-based organogold(III) N-heterocyclic carbene (NHC) (BGC) complexes of general formula [(C^C)Au(NHC-pyr)X], where (C^C) = 4,4'-ditertbutylbiphenyl, X = Cl or phenylacetylide, and (NHC-pyr) is a pyridyl-substituted NHC ligand, the complex BGC4 bearing a 4-CF3-pyridyl substituent and a chloride ligand showed promising antineoplastic activity on the triple negative breast cancer cell line. BGC4 was able to induce cell apoptosis but had no effect on the cell cycle. In vivo, BGC4 reduced the tumor growth rate by increasing the necrosis area and decreasing the mitotic activity. Repeated injections of BGC4 did not induce common side effects. The present investigation shows that BGC4 is a promising antineoplastic candidate. Its potential as a future chemotherapy for the treatment of cancer will be strengthened by evaluating its efficacy in combined treatment with current chemotherapy.

Binuclear Biphenyl Organogold(III) Complexes: Synthesis, Photophysical and Theoretical Investigation, and Anticancer Activity

A series of four binuclear complexes of general formula [(C^C)Au(Cl)(L^L)(Cl)Au(C^C)], where C^C is 4,4'-diterbutylbiphenyl and L^L is either a bridging diphosphine or 4,4'-bipyridine, are synthetized with 52 to 72 % yield and structurally characterized by X-ray diffraction. The use of the chelating 1,2-diphenylphosphinoethane ligand in a 1 : 2 (P^P):Au stoichiometry leads to the near quantitative formation of a gold double-complex salt of general formula [(C^C)Au(P^P)][(C^C^)AuCl2 ]. The compounds display long-lived yellow-green phosphorescence with λem in the range of 525 to 585 nm in the solid state with photoluminescence quantum yields (PLQY) up to 10 %. These AuIII complexes are tested for their antiproliferative activity against lung adenocarcinoma cells A549 and results show that compounds 2 and 5 are the most promising candidates. The digold salt 5 shows anticancer activity between 66 and 200 nM on the tested cancer cell lines, whereas derivative 2 displays concentration values required to reduce by 50 % the cell viability (IC50 ) between 7 and 11 μM. Reactivity studies of compound 5 reveal that the [(C^C)Au(P^P)]+ cation is stable in the presence of relevant biomolecules including glutathione suggesting a structural mechanism of action.

Asymmetrically Coordinated Heterodimetallic Ir-Ru System: Synthesis, Computational, and Anticancer Aspects

Herein, we present an unprecedented formation of a heterodinuclear complex [{(ppy)₂Ir^III}(μ-phpy){Ru^II(tpy)}](ClO₄)₂ {[1](ClO₄)₂} using terpyridyl/phenylpyridine as ancillary ligands and asymmetric phpy as a bridging ligand. The asymmetric binding mode (N^∧N-∩-N^∧N^∧C^-) of the phpy ligand in {[1](ClO₄)₂} is confirmed by ¹H, ¹³C, ¹H-¹H correlated spectroscopy (COSY), high-resolution mass spectrum (HRMS), single-crystal X-ray crystallography techniques, and solution conductivity measurements. Theoretical investigation suggests that the highest occupied molecular orbital (HOMO) and the least unoccupied molecular orbital (LUMO) of [1]²⁺ are located on iridium/ppy and phpy, respectively. The complex displays a broad low energy charge transfer (CT) band within 450-575 nm. The time-dependent density functional theory (TDDFT) analysis suggests this as a mixture of metal-to-ligand charge transfer (MLCT) and ligand-to-ligand charge transfer (LLCT), where both ruthenium, iridium, and ligands are involved. Complex {[1](ClO₄)₂} exhibits Ru^IIIr^III/Ru^IIIIr^III- and Ru^IIIIr^III/Ru^IIIIr^IV-based oxidative couples at 0.83 and 1.39 V, respectively. The complex shows anticancer activity and selectivity toward human breast cancer cells (IC₅₀; MCF-7: 9.3 ± 1.2 μM, and MDA-MB-231: 8.6 ± 1.2 μM) over normal breast cells (MCF 10A: IC₅₀ ≈ 21 ± 1.3 μM). The Western blot analysis and fluorescence microscopy images suggest that combined apoptosis and autophagy are responsible for cancer cell death.

Highlights of New Strategies to Increase the Efficacy of Transition Metal Complexes for Cancer Treatments

Although important progress has been made, cancer still remains a complex disease to treat. Serious side effects, the insurgence of resistance and poor selectivity are some of the problems associated with the classical metal-based anti-cancer therapies currently in clinical use. New treatment approaches are still needed to increase cancer patient survival without cancer recurrence. Herein, we reviewed two promising-at least in our opinion-new strategies to increase the efficacy of transition metal-based complexes. First, we considered the possibility of assembling two biologically active fragments containing different metal centres into the same molecule, thus obtaining a heterobimetallic complex. A critical comparison with the monometallic counterparts was done. The reviewed literature has been divided into two groups: the case of platinum; the case of gold. Secondly, the conjugation of metal-based complexes to a targeting moiety was discussed. Particularly, we highlighted some interesting examples of compounds targeting cancer cell organelles according to a third-order targeting approach, and complexes targeting the whole cancer cell, according to a second-order targeting strategy.

Anticancer and Antibiotic Rhenium Tri- and Dicarbonyl Complexes: Current Research and Future Perspectives

Organometallic compounds are increasingly recognized as promising anticancer and antibiotic drug candidates. Among the transition metal ions investigated for these purposes, rhenium occupies a special role. Its tri- and dicarbonyl complexes, in particular, attract continuous attention due to their relative ease of preparation, stability and unique photophysical and luminescent properties that allow the combination of diagnostic and therapeutic purposes, thereby permitting, e.g., molecules to be tracked within cells. In this review, we discuss the anticancer and antibiotic properties of rhenium tri- and dicarbonyl complexes described in the last seven years, mainly in terms of their structural variations and in vitro efficacy. Given the abundant literature available, the focus is initially directed on tricarbonyl complexes of rhenium. Dicarbonyl species of the metal ion, which are slowly gaining momentum, are discussed in the second part in terms of future perspective for the possible developments in the field.

V, Kar B, Das U, Paira P. Target-specific mononuclear and binuclear rhenium(i) tricarbonyl complexes as upcoming anticancer drugs

Metal complexes have gradually been attracting interest from researchers worldwide as potential cancer therapeutics. Driven by the many side effects of the popular platinum-based anticancer drug cisplatin, the tireless endeavours of researchers have afforded strategies for the design of appropriate metal complexes with minimal side effects compared to cisplatin and its congeners to limit the unrestricted propagation of cancer. In this regard, transition metal complexes, especially rhenium-based complexes are being identified and highlighted as promising cancer theranostics, which are endowed with the ability to detect and annihilate cancer cells in the body. This is attributed the amazing photophysical properties of rhenium complexes together with their ability to selectively attack different organelles in cancer cells. Therefore, this review presents the properties of different rhenium-based complexes to highlight their recent advances as anticancer agents based on their cytotoxicity results.

In this review, rhenium-based complexes are highlighted as promising cancer theranostics, which are endowed with the ability to detect and annihilate cancer cells in the body.

Synthesis of tetranuclear rhenium(I) tricarbonyl metallacycles

Re(I) tricarbonyl complexes have received much attention due to their attractive photochemical, electrochemical, and biological properties. Beyond simple mononuclear complexes, multinuclear assemblies offer greater structural diversity and properties. Despite previous reports on the preparation of di-, tri-, or tetranuclear Re(I) tricarbonyl assemblies, the synthesis of these supramolecular structures remains challenging due to overall low yields or tedious purification protocols. Herein, the facile preparation and characterization of tetranuclear Re(I) tricarbonyl metallacycles with a square geometry is reported using a tetrazole-based ligand. The synthesis of the metallacycle was optimized using different metal precursors, solvents, temperatures, and reagent concentrations. Finally, the scope of suitable tetrazole-based ligands was explored to produce several tetranuclear Re(I) tricarbonyl-based metallacycles.

[(C C)Au(N N)]+ Complexes as a New Family of Anticancer Candidates: Synthesis, Characterization and Exploration of the Antiproliferative Properties

A library of eleven cationic gold(III) complexes of the general formula [(C C)Au(N N)]⁺ when C C is either biphenyl or 4,4'-ditertbutyldiphenyl and N N is a bipyridine, phenanthroline or dipyridylamine derivative have been synthesized and characterized. Contrasting effects on the viability of the triple negative breast cancer cells MDA-MB-231 was observed from a preliminary screening. The antiproliferative activity of the seven most active complexes were further assayed on a larger panel of human cancer cells as well as on non-cancerous cells for comparison. Two complexes stood out for being either highly active or highly selective. Eventually, reactivity studies with biologically meaningful amino acids, glutathione, higher order DNA structures and thioredoxin reductase (TrxR) revealed a markedly different behavior from that of the well-known coordinatively isomeric [(C N C)Au(NHC)]⁺ structure. This makes the [(C C)Au(N N)]⁺ complexes a new class of organogold compounds with an original mode of action.

Photochemistry and in vitro anticancer activity of Pt(IV)Re(I) conjugates

The photophysical and photochemical properties of two Pt(IV)Re(I) conjugates were studied via both experimental and computational methods. Both conjugates exhibit modest photocytotoxicity against ovarian cancer cells. X-ray fluorescence microscopy showed that Pt and Re colocalize in cells whether they had been irradiated or not. This work demonstrates the potential of photoactivated multilimetallic agents for combating cancer.

Heterobimetallic platinum(ii) complexes with increased cytotoxicity against ovarian cancer cell lines

Two series of heterobimetallic compounds were prepared from the starting complex [cis-L2PtCl2] containing an aminophosphine ligand (L = 2,6-iPr2-C6H3-NHPPh2).