Squalenoyl Gemcitabine Monophosphate: Synthesis, Characterisation of Nanoassemblies and Biological Evaluation

Four of a Kind: A Complete Collection of ADP-Ribosylated Histidine Isosteres Using Cu(I)- and Ru(II)-Catalyzed Click Chemistry

Adenosine diphosphate ribosylation (ADP-ribosylation) is a crucial post-translational modification involved in important regulatory mechanisms of numerous cellular pathways including histone maintenance and DNA damage repair. To study this modification, well-defined ADP-ribosylated peptides, proteins, and close analogues thereof have been invaluable tools. Recently, proteomics studies have revealed histidine residues to be ADP-ribosylated. We describe here the synthesis of a complete set of triazole-isosteres of ADP-ribosylated histidine to serve as probes for ADP-ribosylating biomachinery. By exploiting Cu(I)- and Ru(II)-catalyzed click chemistry between a propargylglycine building block and an α- or β-configured azidoribose, we have successfully assembled the α- and β-configured 1,4- and 1,5-triazoles, mimicking N(τ)- and N(π)-ADP-ribosylated histidine, respectively. The ribosylated building blocks could be incorporated into a peptide sequence using standard solid-phase peptide synthesis and transformed on resin into the ADP-ribosylated fragments to provide a total of four ADP-ribosyl triazole conjugates, which were evaluated for their chemical and enzymatic stability. The 1,5-triazole analogues mimicking the N(π)-substituted histidines proved susceptible to base-induced epimerization and the ADP-ribosyl α-1,5-triazole linkage could be cleaved by the (ADP-ribosyl)hydrolase ARH3.

Effect of Alkali Metal Cations on the Unilamellar Vesicle of a Squalene Bearing 18-Crown-6

Squalene bearing 18-crown-6 was synthesized and formed unilamellar vesicles with a membrane thickness of about 6 nm and a diameter of about 0.32 μm. In the wake of the recognition of alkali metal cations, squalene unilamellar vesicles become larger as multilamellar vesicles or smaller while maintaining unilamellar vesicles depending on cations.

Chemical Synthesis of the Antiviral Nucleotide Analogue ddhCTP

3'-Deoxy-3',4'-didehydro-cytidine triphosphate (ddhCTP) is a novel antiviral molecule produced by the enzyme viperin as part of the innate immune response. ddhCTP has been shown to act as an obligate chain terminator of flavivirus and SARS-CoV-2 RNA-dependent RNA polymerases; however, further biophysical studies have been precluded by limited access to this promising antiviral. Herein, we report a robust and scalable synthesis of ddhCTP as well as the mono- and diphosphates ddhCMP and ddhCDP, respectively. Identification of a 2'-silyl ether protection strategy enabled selective synthesis and facile purification of the 5'-triphosphate, culminating in the preparation of ddhCTP on a gram scale.

A unique multidrug nanomedicine made of squalenoyl-gemcitabine and alkyl-lysophospholipid edelfosine

Among anticancer nanomedicines, squalenoyl nanocomposites have obtained encouraging outcomes in a great variety of tumors. The prodrug squalenoyl-gemcitabine has been chosen in this study to construct a novel multidrug nanosystem in combination with edelfosine, an alkyl-lysophopholipid with proven anticancer activity. Given their amphiphilic nature, it was hypothesized that both anticancer compounds, with complementary molecular targets, could lead to the formation of a new multitherapy nanomedicine. Nanoassemblies were formulated by the nanoprecipitation method and characterized by dynamic light scattering, transmission electron microscopy and X-ray photoelectron spectroscopy. Because free edelfosine is highly hemolytic, hemolysis experiments were performed using human blood erythrocytes and nanoassemblies efficacy was evaluated in a patient-derived metastatic pediatric osteosarcoma cell line. It was observed that these molecules spontaneously self-assembled as stable and monodisperse nanoassemblies of 51 ± 1 nm in a surfactant/polymer free-aqueous suspension. Compared to squalenoyl-gemcitabine nanoassemblies, the combination of squalenoyl-gemcitabine with edelfosine resulted in smaller particle size and a new supramolecular conformation, with higher stability and drug content, and ameliorated antitumor profile.

Efficient "green" encapsulation of a highly hydrophilic anticancer drug in metal-organic framework nanoparticles

Metal-organic frameworks (MOFs) are coordination polymers of interest for biomedical applications. Of particular importance, nanoparticles made of iron(III) trimesate (MIL-100, MIL standing for Material Institut Lavoisier) (nanoMOFs) can be conveniently synthesised under mild and green conditions. They were shown to be biodegradable, biocompatible and efficient to encapsulate a variety of active molecules. We have addressed here the challenges to encapsulate a highly hydrophilic anticancer prodrug, phosphated gemcitabin (Gem-MP) known for its instability and inability to bypass cell membranes. MIL-100 nanoMOFs acted as efficient "nanosponges", soaking Gem-MP from its aqueous solution with almost perfect efficiency (>98%). Maximal loadings reached ∼30 wt% reflecting the strong interaction between the drug and the iron trimesate matrices. Neither degradation nor loss of crystalline structure was observed after the loading process. Storage of the loaded nanoMOFs in water did not result in drug release over three days. However, Gem-MP was released in media containing phosphates, as a consequence to particle degradation. Drug-loaded nanoMOFs were effective against pancreatic PANC-1 cells, in contrast to free drug and empty nanoMOFs. However, an efflux phenomenon could contribute to reduce the efficacy of the nanocarriers. Size optimization and surface modification of the nanoMOFs are expected to further improve these findings.

How can nanomedicines overcome cellular-based anticancer drug resistance?

This review discusses the mechanisms of anticancer drug resistance according to its cellular level of action and outlines the nanomedicine-based strategies adopted to overcome it.

The role of solvent swelling in the self-assembly of squalene based nanomedicines

Squalene based nanoparticles obtained via nanoprecipitation are promising candidates as efficient anti-cancer drugs. In order to highlight their preparation process and to facilitate further clinical translation, the present study enlightens the paramount role of the solvent in the formation of these nanomedicines. Three different squalene-based nanoparticles, i.e. squalenic acid, deoxycytidine squalene and gemcitabine squalene, have been investigated before and after organic solvent evaporation. Size and structural analysis by Small Angle Neutron Scattering revealed that droplets' size was uniquely controlled by the solvent composition (ethanol-water), which evolved during their gradual formation. The particles were preferably swollen by water and the swelling increased when less ethanol was present. Either coalescence or fragmentation was observed depending on the increase or decrease of the ethanol content, supporting an equilibrium control of the size. Moreover, a high water swelling was observed for the three local organization of the nanodroplets (hexagonal for gemcitabine squalene, cubic for deoxycytidine and not structured for squalenic acid) and could be the source of the previously reported efficiency of related anti-cancer squalene based nanomedicines.

Lipid prodrug nanocarriers in cancer therapy

Application of nanotechnology in the medical field (i.e., nanomedicine) plays an important role in the development of novel drug delivery methods. Nanoscale drug delivery systems can indeed be customized with specific functionalities in order to improve the efficacy of the treatments. However, despite the progresses of the last decades, nanomedicines still face important obstacles related to: (i) the physico-chemical properties of the drug moieties which may reduce the total amount of loaded drug; (ii) the rapid and uncontrolled release (i.e., burst release) of the encapsulated drug after administration and (iii) the instability of the drug in biological media where a fast transformation into inactive metabolites can occur. As an alternative strategy to alleviate these drawbacks, the prodrug approach has found wide application. The covalent modification of a drug molecule into an inactive precursor from which the drug will be freed after administration offers several benefits such as: (i) a sustained drug release (mediated by chemical or enzymatic hydrolysis of the linkage between the drug-moiety and its promoiety); (ii) an increase of the drug chemical stability and solubility and, (iii) a reduced toxicity before the metabolization occurs. Lipids have been widely used as building blocks for the design of various prodrugs. Interestingly enough, these lipid-derivatized drugs can be delivered through a nanoparticulate form due to their ability to self-assemble and/or to be incorporated into lipid/polymer matrices. Among the several prodrugs developed so far, this review will focus on the main achievements in the field of lipid-based prodrug nanocarriers designed to improve the efficacy of anticancer drugs. Gemcitabine (Pubchem CID: 60750); 5-fluorouracil (Pubchem CID: 3385); Doxorubicin (Pubchem CID: 31703); Docetaxel (Pubchem CID: 148124); Methotrexate (Pubchem CID: 126941); Paclitaxel (Pubchem CID: 36314).

Gemcitabine-based therapy for pancreatic cancer using the squalenoyl nucleoside monophosphate nanoassemblies

Gemcitabine is currently the most effective agent against advanced pancreatic cancer. However, the major therapeutic hurdles using gemcitabine include rapid inactivation by blood deaminases and fast development of cell chemoresistance, induced by down-regulation of deoxycytidine kinase or nucleoside transporters. To overcome the above drawbacks we designed recently a novel nanomedicine strategy based on squalenoyl prodrug of 5'-monophosphate gemcitabine (SQdFdC-MP). This amphiphilic conjugate self-organized in water into unilamellar vesicles with a mean diameter of 100 nm. In this study the antitumor efficacy of SQdFdC-MP nanoassemblies (NAs) on chemoresistant and chemosensitive pancreatic adenocarcinoma models have been investigated. Cell viability assays showed that SQdFdC-MP NAs displayed higher antiproliferative and cytotoxic effects, particularly in chemoresistant pancreatic tumor cells. In in vivo studies, SQdFdC-MP NAs decreased significantly the growth (∼70%) of human MiaPaCa2 xenografts, also preventing tumor cell invasion, whereas native dFdC did not display any anticancer activity when tumor growth inhibition was only 35% with SQdFdC NAs. These results correlated with a reduction of Ki-67 antigen and the induction of apoptosis mediated by caspase-3 activation in tumor cells. These findings demonstrated the feasibility of utilizing SQdFdC-MP NAs to make tumor cells more sensitive to gemcitabine and thus providing an efficient new therapeutic alternative for pancreatic adenocarcinoma.

Self-assembly of squalene-based nucleolipids: relating the chemical structure of the bioconjugates to the architecture of the nanoparticles

Squalene-based nucleolipids, including anticancer or antiviral prodrugs, gave rise to nanoparticles displaying a diversity of structures upon nanoprecipitation in water. Synchrotron small-angle X-ray scattering and cryo-TEM imaging revealed that both the nature of the nucleoside and the position of the squalene moiety relative to the nucleobase determined the self-assembly of the corresponding bioconjugates. It was found that small chemical differences resulted in major differences in the self-organization of nucleolipids when squalene was grafted onto the nucleobase whereas only lamellar phases were observed when squalene was linked to the sugar moiety. The key role of hydrogen bonds between nucleobases in the formation of the lamellar phases was suggested, in agreement with molecular simulations. These findings provide a way to fine tune the supramolecular organization of squalene-based prodrugs, with the aim of improving their pharmacological activity.