Sulfonamide-containing copper(II) metallonucleases: Correlations with in vitro antimycobacterial and antiproliferative activities

Copper-Based Antibiotic Strategies: Exploring Applications in the Hospital Setting and the Targeting of Cu Regulatory Pathways and Current Drug Design Trends

Classical antibacterial drugs were designed to target specific bacterial properties distinct from host human cells to maximize potency and selectivity. These designs were quite effective as they could be easily derivatized to bear next-generation drugs. However, the rapid mutation of bacteria and their associated acquired drug resistance have led to the rise of highly pathogenic superbug bacterial strains for which treatment with first line drugs is no match. More than ever, there is a dire need for antibacterial drug design that goes beyond conventional standards. Taking inspiration by the body's innate immune response to employ its own supply of labile copper ions in a toxic attack against pathogenic bacteria, which have a very low Cu tolerance, this review article examines the feasibility of Cu-centric strategies for antibacterial preventative and therapeutic applications. Promising results are shown for the use of Cu-containing materials in the hospital setting to minimize patient bacterial infections. Studies directed at disrupting bacterial Cu regulatory pathways elucidate new drug targets that can enable toxic increase of Cu levels and perturb bacterial dependence on iron. Likewise, Cu intracellular chelation/prochelation strategies effectively induce bacterial Cu toxicity. Cu-based small molecules and nanoparticles demonstrate the importance of the Cu ions in their mechanism and display potential synergism with classical drugs.

Insights into the role of the cobalt(III)-thiosemicarbazone complex as a potential inhibitor of the Chikungunya virus nsP4

Chikungunya virus (CHIKV) is the causative agent of chikungunya fever, a disease that can result in disability. Until now, there is no antiviral treatment against CHIKV, demonstrating that there is a need for development of new drugs. Studies have shown that thiosemicarbazones and their metal complexes possess biological activities, and their synthesis is simple, clean, versatile, and results in high yields. Here, we evaluated the mechanism of action (MOA) of a cobalt(III) thiosemicarbazone complex named [CoIII(L1)2]Cl based on its in vitro potent antiviral activity against CHIKV previously evaluated (80% of inhibition on replication). Furthermore, the complex has no toxicity in healthy cells, as confirmed by infecting BHK-21 cells with CHIKV-nanoluciferase in the presence of the compound, showing that [CoIII(L1)2]Cl inhibited CHIKV infection with the selective index of 3.26. [CoIII(L1)2]Cl presented a post-entry effect on viral replication, emphasized by the strong interaction of [CoIII(L1)2]Cl with CHIKV non-structural protein 4 (nsP4) in the microscale thermophoresis assay, suggesting a potential mode of action of this compound against CHIKV. Moreover, in silico analyses by molecular docking demonstrated potential interaction of [CoIII(L1)2]Cl with nsP4 through hydrogen bonds, hydrophobic and electrostatic interactions. The evaluation of ADME-Tox properties showed that [CoIII(L1)2]Cl presents appropriate lipophilicity, good human intestinal absorption, and has no toxicological effect as irritant, mutagenic, reproductive, and tumorigenic side effects.

Antiproliferative Copper(II) Complexes Bearing Mixed Chelating Ligands: Structural Characterization, ROS Scavenging, In Silico Studies, and Anti-Melanoma Activity

Melanoma is a skin cancer characterized by rapid growth and spread for which current therapies produce both resistance and increased risk of infection. To develop new anti-melanoma biocompatible species, the series of complexes Cu(N-N)(bzac)(X)⋅nH₂O (N-N: 1,10-phenanthroline/2,2′-bipyridine, Hbzac: 1-phenyl-1,3-butanedione, X: NO₃/ClO₄, and n = 0, 1) was studied. Single-crystal X-ray diffraction revealed a mononuclear structure for all complexes. The ability of the complexes to scavenge or trap reactive oxygen species such as O₂⋅⁻ and HO⋅ was proved by EPR spectroscopy experiments. All complexes inhibited B16 murine melanoma cells in a dose-dependent and nanomolar range, but the complexes with 1,10-phenanthroline were more active. Moreover, comparative activity on B16 and healthy BJ cells revealed a therapeutic index of 1.27–2.24. Bioinformatic methods were used to calculate the drug-likeness, pharmacokinetic, pharmacogenomic, and pharmacodynamic profiles of the compounds. The results showed that all compounds exhibit drug-likeness features, as well as promising absorption, distribution, metabolism, and excretion (ADME) properties, and no toxicity. The pharmacodynamics results showed that the neutral species appear to be good candidates for antitumor molecular targets (Tyrosyl-DNA phosphodiesterase 1, DNA-(apurinic or apyrimidinic site) lyase or Kruppel-like factor 5). Furthermore, the pharmacogenomic results showed a good affinity of the copper(II) complexes for the human cytochrome. These results recommend complexes bearing 1,10-phenanthroline as good candidates for developing drugs to melanoma alternative treatment.

Nuclease-like metalloscissors: Biomimetic candidates for cancer and bacterial and viral infections therapy

Despite the extensive and rapid discovery of modern drugs for treatment of cancer, microbial infections, and viral illnesses; these diseases are still among major global health concerns. To take inspiration from natural nucleases and also the therapeutic potential of metallopeptide antibiotics such as the bleomycin family, artificial metallonucleases with the ability of promoting DNA/RNA cleavage and eventually affecting cellular biological processes can be introduced as a new class of therapeutic candidates. Metal complexes can be considered as one of the main categories of artificial metalloscissors, which can prompt nucleic acid strand scission. Accordingly, biologists, inorganic chemists, and medicinal inorganic chemists worldwide have been designing, synthesizing and evaluating the biological properties of metal complexes as artificial metalloscissors. In this review, we try to highlight the recent studies conducted on the nuclease-like metalloscissors and their potential therapeutic applications. Under the light of the concurrent Covid-19 pandemic, the human need for new therapeutics was highlighted much more than ever before. The nuclease-like metalloscissors with the potential of RNA cleavage of invading viral pathogens hence deserve prime attention.

Repurposing potential of rimantadine hydrochloride and development of a promising platinum(II)-rimantadine metallodrug for the treatment of Chikungunya virus infection

Most of the patients infected with Chikungunya virus (CHIKV) develop chronic manifestations characterized by pain and deformity in joints, impacting their quality of life. The aminoadamantanes, in their turn, have been exploited due to their biological activities, with amantadine and memantine recently described with anti-CHIKV activities. Here we evaluated the antiviral activity of rimantadine hydrochloride (rtdH), a well-known antiviral agent against influenza A, its platinum complex (Pt-rtd), and the precursor cis-[PtCl₂(dmso)₂], against CHIKV infection in vitro. The rtdH demonstrated significant antiviral activity in all stages of CHIKV replication (29% in pre-treatment; 57% in early stages of infection; 60% in post-entry stages). The Pt-rtd complex protected the cells against infection in 92%, inhibited 100% of viral entry, mainly by a virucidal effect, and impaired 60% of post-entry stages. Alternatively, cis-[PtCl₂(dmso)₂] impaired viral entry in 100% and post-entry steps in 60%, but had no effect in protecting cells when administered prior to CHIKV infection. Collectively, the obtained data demonstrated that rtdH and Pt-rtd significantly interfered in the early stages of CHIKV life cycle, with the strongest effect observed to Pt-rtd complex, which reduced up to 100% of CHIKV infection. Moreover, molecular docking analysis and infrared spectroscopy data (ATR-FTIR) suggest an interaction of Pt-rtd with CHIKV glycoproteins, potentially related to the mechanism of inhibition of viral entry by Pt-rtd. Through a migration retardation assay, it was also shown that Pt-rtd and cis-[PtCl₂(dmso)₂] interacted with the dsRNA in 87% and 100%, respectively. The obtained results highlight the repurposing potential of rtdH as an anti-CHIKV drug, as well as the synthesis of promising platinum(II) metallodrugs with potential application for the treatment of CHIKV infections. Importance Chikungunya fever is a disease that can result in persistent symptoms due to the chronic infection process. Infected patients can develop physical disability, resulting and high costs to the health system and significant impacts on the quality of life of affected individuals. Additionally, there are no licensed vaccines or antivirals against the Chikungunya virus (CHIKV) and the virus is easily transmitted due to the abundance of viable vectors in epidemic regions. In this context, our study highlights the repurposing potential of the commercial drug rimantadine hydrochloride (rtdH) as an antiviral agent for the treatment of CHIKV infections. Moreover, our data demonstrated that a platinum(II)-rimantadine metallodrug (Pt-rtd) poses as a potent anti-CHIKV molecule with potential application for the treatment of Chikungunya fever. Altogether, rtdH and Pt-rtd significantly interfered in the early stages of CHIKV life cycle, reducing up to 100% of CHIKV infection in vitro.

An overview of sulfonamide-based conjugates: Recent advances for tuberculosis treatment

In 2019, tuberculosis (TB) caused approximately 1.4 million deaths around the world. TB is an infectious respiratory disease mainly caused by Mycobacterium tuberculosis. The lack of new drugs to treat drug-resistant strains is a principal factor for the continuous slow rise in TB infections. Sulfonamides are active moieties in various drugs used against several sicknesses, including TB. Our aim is to aid the development of new TB treatments and drugs by describing recent improvements (2011-2021) to sulfonamide-based compounds.

Ternary Copper Complex of L-Glutamine and Phenanthroline as Counterions of Cyclo-Tetravanadate Anion: Experimental–Theoretical Characterization and Potential Antineoplastic Activity

Over the last decade, therapeutic metallodrugs have become substantially effective in the treatment of cancer. Thus, developing new effective anticancer drugs is a significant research area against the continuing increase in cancers worldwide. In the search for heterobimetallic prodrugs containing V/Cu, a new cyclo-tetravanadate was synthesized and characterized by UV-visible and FTIR spectroscopies and single-crystal X-ray diffraction. L-Glutamine and 1,10-phenanthroline allow the crystallization of [Cu(L-Gln)(phen)(H2O)]4[V4O12]∙8(H2O) (1), in which the cyclo-tetravanadate acts as a free anion. Density functional theory (DFT) calculations were carried out to characterize the frontier molecular orbitals and molecular electrostatic potential. Global reactivity indexes were calculated and analyzed to give insight into the cyclo-tetravanadate anion and complex counterions interactions. Also, using Bader’s theory of atoms in molecules (AIM), non-covalent interactions were analyzed. Docking analysis with the Casiopeina-like complex resulting from the hydrolysis of compound 1 provided insights into these complex potential anticancer activities by interacting with DNA/tRNA via H-bonds and hydrophobic interactions. The release of both components could act together or separately, acting as prodrugs with potential dual antineoplastic activities.

Recent advances in drug discovery against Mycobacterium tuberculosis: Metal-based complexes

Metal-based drugs are privileged motifs that act as primary pharmacophores in bioactive compounds for various diseases, including tuberculosis (TB). This potentially life-threatening and extremely contagious infectious disease is caused by Mycobacterium tuberculosis (Mtb). In 2018, TB infected about 10 million people and caused 1.2 million deaths worldwide. A large number of ligands are promising scaffolds in drug design, including heterocyclic, phosphines, schiff bases, thio and semicarbazones, aliphatic amines, cyclopalladated, cyanometallates and miscellaneous. Moreover, several metal-based complexes have been studied for the treatment of numerous illnesses, including infectious diseases. To contribute to drug design, we identified the metal-based organometallic complexes against Mtb. Thus, in this review article, we analysed the recent contributions of metal-based scaffolds for design of new anti-Mtb drugs in the last decade (2011-2020). Besides, metal-based approaches will be presented in order to find out new antitubercular agents.

Copper(II) Complexes with Mixed Heterocycle Ligands as Promising Antibacterial and Antitumor Species

Complexes with mixed ligands [Cu(N-N)₂(pmtp)](ClO₄)₂ ((1) N-N: 2,2′-bipyridine; (2) L: 1,10-phenanthroline and pmpt: 5-phenyl-7-methyl-1,2,4-triazolo[1,5-a]pyrimidine) were synthesized and structurally and biologically characterized. Compound (1) crystallizes into space group Pa and (2) in P-1. Both complexes display an intermediate stereochemistry between the two five-coordinated ones. The biological tests indicated that the two compounds exhibited superoxide scavenging capacity, intercalative DNA properties, and metallonuclease activity. Tests on various cell systems indicated that the two complexes neither interfere with the proliferation of Saccharomyces cerevisiae or BJ healthy skin cells, nor cause hemolysis in the active concentration range. Nevertheless, the compounds showed antibacterial potential, with complex (2) being significantly more active than complex (1) against all tested bacterial strains, both in planktonic and biofilm growth state. Both complexes exhibited a very good activity against B16 melanoma cells, with a higher specificity being displayed by compound (1). Taken together, the results indicate that complexes (1) and (2) have specific biological relevance, with potential for the development of antitumor or antimicrobial drugs.

Copper transporter 1 affinity as a delivery strategy to improve the cytotoxic profile of rationally designed copper(II) complexes for cancer treatment

Cisplatin is widely used to treat different types of cancer, but its severe side effects are the major disadvantage of this treatment. Therefore, other metals are currently the subject of research in the rational development of anticancer drugs, such as copper, that has been demonstrated to be promising in this scenario. Here, we evaluated the effects of two novel copper complexes against breast cancer cell lines, and also examined the influence of overexpressing copper transporter 1 (CTR1) on the cytotoxicity of these complexes. Complex (1) [Cu(sdmx^-)₂(phen)] showed low IC₅₀ values, induced intense cell morphological changes and arrested the cell cycle at the sub-G1 phase in cancer cells. Complex (1) was tested in transfected cells overexpressing the CTR1 receptor in order to compare its steric effects with a less bulky ligand and more labile complex (2) [CuCl₂(impy)]. A significant reduction of IC₅₀ value was observed in CTR1 overexpressing cells for complex (2) (32 μM to 20 μM) as compared to (1) (2.78 μM to 3.41 μM), evidencing a possible uptake through copper reduction (Cu⁺² → Cu⁺¹) mediated by CTR1. Thus, considering that CTR1 is a mediator of metallodrugs uptake, the development of strategies that use rational drug design is important in order to improve the therapeutic efficacy through greater specificity and consecutive reduction of side effects. Here we show the example for the case of copper(II) complexes.

Metal-Peptide Complexes as Promising Antibiotics to Fight Emerging Drug Resistance: New Perspectives in Tuberculosis

In metal-peptide interactions, cations form stable complexes through bonds with coordinating groups as side chains of amino acids. These compounds, among other things, exert a wide variety of antimicrobial activities through structural changes of peptides upon metal binding and redox chemistry. They exhibit different mechanisms of action (MOA), including the modification of DNA/RNA, protein and cell wall synthesis, permeabilization and modulation of gradients of cellular membranes. Nowadays, the large increase in antibiotic resistance represents a crucial problem to limit progression at the pandemic level of the diseases that seemed nearly eradicated, such as tuberculosis (Tb). Mycobacterium tuberculosis (Mtb) is intrinsically resistant to many antibiotics due to chromosomal mutations which can lead to the onset of novel strains. Consequently, the maximum pharmaceutical effort should be focused on the development of new therapeutic agents and antimicrobial peptides can represent a valuable option as a copious source of potential bioactive compounds. The introduction of a metal center can improve chemical diversity and hence specificity and bioavailability while, in turn, the coordination to peptides of metal complexes can protect them and enhance their poor water solubility and air stability: the optimization of these parameters is strictly required for drug prioritization and to obtain potent inhibitors of Mtb infections with novel MOAs. Here, we present a panoramic review of the most recent findings in the field of metal complex-peptide conjugates and their delivery systems with the potential pharmaceutical application as novel antibiotics in Mtb infections.

An Oxalate-Bridged Copper(II) Complex Combining Monodentate Benzoate, 2,2'-bipyridine and Aqua Ligands: Synthesis, Crystal Structure and Investigation of Magnetic Properties

A dinuclear copper(II) complex of formula [{Cu(bipy)(bzt)(OH₂)}₂(μ-ox)] (1) (where bipy = 2,2′-bipyridine, bzt = benzoate and ox = oxalate) was synthesised and characterised by diffractometric (powder and single-crystal XRD) and thermogravimetric (TG/DTG) analyses, spectroscopic techniques (IR, Raman, electron paramagnetic resonance spectroscopy (EPR) and electronic spectroscopy), magnetic measurements and density functional theory (DFT) calculations. The analysis of the crystal structure revealed that the oxalate ligand is in bis(bidentate) coordination mode between two copper(II) centres. The other four positions of the coordination environment of the copper(II) ion are occupied by one water molecule, a bidentate bipy and a monodentate bzt ligand. An inversion centre located on the ox ligand generates the other half of the dinuclear complex. Intermolecular hydrogen bonds and π-π interactions are responsible for the organisation of the molecules in the solid state. Molar magnetic susceptibility and field dependence magnetisation studies evidenced a weak intramolecular–ferromagnetic interaction (J = +2.9 cm⁻¹) between the metal ions. The sign and magnitude of the calculated J value by density functional theory (DFT) are in agreement with the experimental data.

Synthesis, crystal structures, DFT studies, antibacterial assays and interaction assessments with biomolecules of new platinum(ii) complexes with adamantane derivatives

Synthesis, crystal structures and antibacterial activities of new Pt(ii) complexes with adamantane derivatives are presented in this article.

Sulfonamide-containing copper(ii) complexes: new insights on biophysical interactions and antibacterial activities

Cu–(N^N)–sulfonamide complexes are selective metallonucleases that bind tightly to BSA with no protease activity. These compounds have promising antibacterial properties.

Ternary copper(II) complex of 5-hydroxytryptophan and 1,10-phenanthroline with several pharmacological properties and an adequate safety profile

We report the synthesis and biological evaluation of a ternary copper complex, [Cu(5HTP)(phen)(H₂O)](NO₃).2H₂O, with the antioxidant agent 5-hydroxytryptophan (5-HTP) and phenanthroline (phen, added to improve its lipophilicity and membrane transport). The crystal structure of the complex was determined by X-ray diffraction methods. The complex showed antioxidant, antimicrobial, antitumor and antimetastatic properties with an adequate safety profile. The interaction of the metal with phen promotes cellular copper accumulation and cytotoxicity on human lung A549 cell line (IC₅₀ = 3.6 μM). Furthermore, the viability of the normal human fetal lung fibroblast cell line (MRC-5) is not altered by the complex. An oxidative stress mechanism for the anticancer effect has been determined: cellular increase of reactive oxygen species (ROS), decrease of the glutathione (GSH) and oxidized GSH (GSSG) ratio and alteration of the mitochondrial potential. The complex also displays antimetastatic activities with inhibition of cell adhesion, invasion and migration. It has not mutagenic behavior and no toxicity on Artemia salina indicating its potential to act as an effective and safety antimicrobial and antitumor drug.