Mechanistic Evaluations of the Effects of Auranofin Triethylphosphine Replacement with a Trimethylphosphite Moiety

Multinuclear Silver(I)-Selenium Clusters Formation in Selenopeptides

The reactions of ionic silver (Ag+) with arginine vasopressin (AVP), a nonapeptide hormone cyclized by two cysteine residues, and its diselenium analogue was explored by an integrated LC-MS, UV-vis, and DFT approach. The replacement of Cys by SeCys in AVP increased the reactivity of the peptide toward Ag+ ions under mildly reducing conditions, with the formation of a Se4Ag4 cluster provided by Ag(I)-mediated dimerization of diselenide AVP. Specific electronic absorption bands confirmed the formation of the Ag4peptide2 complex, supported by DFT calculations. These results provide the first ever evidence that Ag(I) ions bind a selenopeptide and prefer SeCys over Cys as binding sites, opening a perspective on the involvement of selenobiomolecules in the emerging cellular toxicity of silver.

Strategies for the design of analogs of auranofin endowed with anticancer potential

INTRODUCTION

Auranofin (AF) is a well-established, FDA-approved, antiarthritic gold drug that is currently being reevaluated for a variety of therapeutic indications through drug repurposing. AF has shown great promise as a potential anticancer agent and has been approved for a few clinical trials in cancer. The renewed interest in AF has led to extensive research into the design, preparation and biological evaluation of auranofin analogs, which may have an even better pharmacological profile than the parent drug.

AREAS COVERED

This article reviews the strategies for chemical modification of the AF scaffold. Several auranofin analogs have been prepared and characterized for medical application in the field of cancer treatment over the last 20 years. Some emerging structure-function relationships are proposed and discussed.

EXPERT OPINION

The chemical modification of the AF scaffold has been the subject of intense activity in recent years and this strategy has led to the preparation and evaluation of several AF analogs. The case of iodauranofin is a particularly promising example. The availability of homogeneous biological data for a group of AF derivatives allows some initial structure-function relationships to be proposed, which may inspire the design and synthesis of new and better AF analogs for cancer treatment.

Study of metalation of thioredoxin by gold(I) therapeutic compounds using combined liquid chromatography/capillary electrophoresis with inductively coupled plasma/electrospray MS/MS detection

The reactivity of thioredoxin (Trx1) with the Au(I) drug auranofin (AF) and two therapeutic N-heterocyclic carbene (NHC)2-Au(I) complexes (bis [1-methyl-3-acridineimidazolin-2-ylidene]gold(I) tetrafluoroborate (Au3BC) and [1,3-diethyl-4,5-bis(4methoxyphenyl)imidazol-2-ylidene]gold(I) (Au4BC)) was investigated. Direct infusion (DI) electrospray ionization (ESI) mass spectrometry (MS) allowed information on the structure, stoichiometry, and kinetics of formation of Trx-Au adducts. The fragmentation of the formed adducts in the gas phase gave insights into the exact Au binding site within the protein, demonstrating the preference for Trx1 Cys32 or Cys35 of AF or the (NHC)2-Au(I) complex Au3BC, respectively. Reversed-phase HPLC suffered from the difficulty of elution of gold compounds, did not preserve the formed metal-protein adducts, and favored the loss of ligands (phosphine or NHC) from Au(I). These limitations were eliminated by capillary electrophoresis (CE) which enabled the separation of the gold compounds, Trx1, and the formed adducts. The ICP-MS/MS detection allowed the simultaneous quantitative monitoring of the gold and sulfur isotopes and the determination of the metallation extent of the protein. The hyphenation of the mentioned techniques was used for the analysis of Trx1-Au adducts for the first time.

Gold-Promoted Biocompatible Selenium Arylation of Small Molecules, Peptides and Proteins

A low pKa (5.2), high polarizable volume (3.8 Å), and proneness to oxidation under ambient conditions make selenocysteine (Sec, U) a unique, natural reactive handle present in most organisms across all domains of life. Sec modification still has untapped potential for site-selective protein modification and probing. Herein we demonstrate the use of a cyclometalated gold(III) compound, [Au(bnpy)Cl2 ], in the arylation of diselenides of biological significance, with a scope covering small molecule models, peptides, and proteins using a combination of multinuclear NMR (including 77 Se NMR), and LC-MS. Diphenyl diselenide (Ph-Se)2 and selenocystine, (Sec)2 , were used for reaction optimization. This approach allowed us to demonstrate that an excess of diselenide (Au/Se-Se) and an increasing water percentage in the reaction media enhance both the conversion and kinetics of the C-Se coupling reaction, a combination that makes the reaction biocompatible. The C-Se coupling reaction was also shown to happen for the diselenide analogue of the cyclic peptide vasopressin ((Se-Se)-AVP), and the Bos taurus glutathione peroxidase (GPx1) enzyme in ammonium acetate (2 mM, pH=7.0). The reaction mechanism, studied by DFT revealed a redox-based mechanism where the C-Se coupling is enabled by the reductive elimination of the cyclometalated Au(III) species into Au(I).