Dual Gene Delivery Reagents From Antiproliferative Alkylphospholipids for Combined Antitumor Therapy.

Alkylphospholipids (APLs) have elicited great interest as antitumor agents due to their unique mode of action on cell membranes. However, their clinical applications have been limited so far by high hemolytic activity. Recently, cationic prodrugs of erufosine, a most promising APL, have been shown to mediate efficient intracellular gene delivery, while preserving the antiproliferative properties of the parent APL. Here, cationic prodrugs of the two APLs that are currently used in the clinic, miltefosine, and perifosine, are investigated and compared to the erufosine prodrugs. Their synthesis, stability, gene delivery and self-assembly properties, and hemolytic activity are discussed in detail. Finally, the potential of the pro-miltefosine and pro-perifosine compounds M E12 and P E12 in combined antitumor therapy is demonstrated using pUNO1-hTRAIL, a plasmid DNA encoding TRAIL, a member of the TNF superfamily. With these pro-APL compounds, we provide a proof of concept for a new promising strategy for cancer therapy combining gene therapy and APL-based chemotherapy.

Synthesis and Evaluation of Antitumor Alkylphospholipid Prodrugs.

PURPOSE: Hemolysis is a serious side effect of antitumor alkylphospholipids (APLs) that limits dose levels and is a constraint in their use in therapeutic regimen. Nine prodrugs of promising APLs (miltefosine, perifosine, and erufosine) were synthesized so as to decrease their membrane activity and improve their toxicity profile while preserving their antineoplastic potency. METHODS: The synthesis of the pro-APLs was straightforwardly achieved in one step starting from the parent APLs. The critical aggregation concentration of the prodrugs, their hydrolytic stability under various pH conditions, their blood compatibility and cytotoxicity in three different cell lines were determined and compared to those of the parent antitumor lipids. RESULTS: The APL prodrugs display antitumor activity which is similar to that of the parent alkylphospholipids but without associated hemolytic toxicity. CONCLUSION: The pro-APL compounds may be considered as intravenously injectable derivatives of APLs. They could thus address one of the major issues met in cancer therapies involving antitumor lipids and restricting their utilization to oral and topical administration because of limited maximum tolerated dose.

Erufosine (ErPC3) Cationic Prodrugs as Dual Gene Delivery Reagents for Combined Antitumor Therapy.

Sixteen cationic prodrugs of the antitumor alkylphospholipid (APL) erufosine were rationally synthesized to provide original gene delivery reagents with improved cytotoxicity profile. The DNA complexation properties of these cationic lipids were determined and associated transfection rates were measured. Furthermore, the self-assembly properties of the pro-erufosine compounds were investigated and their critical aggregation concentration was determined. Their hydrolytic stability under pH conditions mimicking the extracellular environment and the late endosome milieu was measured. Hemolytic activity and cytotoxicity of the compounds were investigated. The results obtained in various cell lines demonstrate that the prodrugs of erufosine display antineoplastic activity similar to that of the parent antitumor drug but are not associated with hemolytic toxicity, which is a dose-limiting side effect of APLs and a major obstacle to their use in anticancer therapeutic regimen. Furthermore, by using lipoplexes prepared from a prodrug of erufosine and a plasmid DNA encoding a pro-apoptotic protein (TRAIL), evidence was provided for selective cytotoxicity towards tumor cells while nontumor cells were resistant. This study demonstrates that the combination approach involving well tolerated erufosine cationic prodrugs and cancer gene therapy holds significant promise in tumor therapy.

Design and evaluation of ionizable peptide amphiphiles for siRNA delivery.

Small interfering RNAs (siRNAs) can down-regulate the expression of a target mRNA molecule in a sequence-specific manner, making them an attractive new class of drugs with broad potential for the treatment of diverse human diseases. Here, we report the synthesis of a series of cationic amphiphiles which were obtained by the coupling of amino acids and dipeptides onto a lipidic double chain. The new amphiphiles presenting a peptidic motif on a short hydrophilic spacer group were evaluated for selective gene silencing through RNA interference. Our results show that tryptophan residues boost siRNA delivery in an unexpected manner. The silencing experiments performed with very low concentrations of siRNA showed that the best formulations could induce significant death of tumor cells after silencing of polo-like kinase 1 which is implicated in cell cycle progression. In addition, these Trp containing peptide amphiphiles were highly efficient siRNA delivery vectors even in presence of competing serum proteins.

Cationic Photopolymerized Polydiacetylenic (PDA) Micelles for siRNA Delivery.

Polymerized micelles obtained by photopolymerization of diacetylenic surfactants and which are forming polydiacetylenic systems (PDAs) have recently gained interest as stabilized monodisperse systems showing potential for the delivery of hydrophobic drugs as well as of larger biomolecules such as nucleic acids. Introduction of pH-sensitive histidine groups at the surface of the micellar PDA systems allows for efficient delivery of siRNA resulting in specific gene silencing through RNA interference. Here, we describe the detailed experimental procedure for the reproducible preparation of these photopolymerized PDA micelles. We provide physicochemical characterization of these nanomaterials by dynamic light scattering, transmission electron microscopy, and diffusion ordered spectroscopy. Moreover, we describe standardized biological tests to evaluate the silencing efficiency by the use of a cell line constitutively expressing the luciferase reporter gene.

Cationic Oligospermine-Oligonucleotide Conjugates Provide Carrier-free Splice Switching in Monolayer Cells and Spheroids.

We report the evaluation of 18-mer 2'-O-methyl-modified ribose oligonucleotides with a full-length phosphorothioate backbone chemically conjugated at the 5' end to the oligospermine units (Sn-: n = 5, 15, 20, 25, and 30 [number of spermine units]) as splice switching oligonucleotides (SSOs). These conjugates contain, in their structure, covalently linked oligocation moieties, making them capable of penetrating cells without transfection vector. In cell culture, we observed efficient cytoplasmic and nuclear delivery of fluorescein-labeled S20-SSO by fluorescent microscopy. The SSO conjugates containing more than 15 spermine units induced significant carrier-free exon skipping at nanomolar concentration in the absence and in the presence of serum. With an increasing number of spermine units, the conjugates became slightly toxic but more active. Advantages of these molecules were particularly demonstrated in three-dimensional (3D) cell culture (multicellular tumor spheroids [MCTSs]) that mimics living tissues. Whereas vector-complexed SSOs displayed a drastically reduced splice switching in MCTS compared with the assay in monolayer culture, an efficient exon skipping without significant toxicity was observed with oligospermine-grafted SSOs (S15- and S20-SSOs) transfected without vector. It was shown, by flow cytometry and confocal microscopy, that the fluorescein-labeled S20-SSO was freely diffusing and penetrating the innermost cells of MCTS, whereas the vector-complexed SSO penetrated only the cells of the spheroid's outer layer.

Co-delivery of anti-PLK-1 siRNA and camptothecin by nanometric polydiacetylenic micelles results in a synergistic cell killing.

Recently, it has been shown that the efficiency of antitumoral drugs can be enhanced when combined with therapeutic siRNAs. In the present study, an original platform based on polydiacetylenic micelles containing a cationic head group able to efficiently deliver a small interfering RNA (siRNA) targeting the PLK-1 gene while offering a hydrophobic environment for encapsulation of lipophilic drugs such as camptothecin is developed. We demonstrate that the co-delivery of these two agents with our micellar system results in a synergistic tumor cell killing of cervical and breast cancer cell lines in vitro. The combined drugs are active in a subcutaneous in vivo cancer model. Altogether, the results show that our nanometric micellar delivery system can be used for the development of new drug-siRNA combo-therapies.

pH-Responsive Nanometric Polydiacetylenic Micelles Allow for Efficient Intracellular siRNA Delivery.

A novel generation of pH-responsive photopolymerized diacetylenic amphiphile (PDA) micelles with a diameter of 10 nm was designed and optimized for the intracellular delivery of siRNAs. Dialysis and photopolymerization of the micelles allowed a strong reduction of the cytotoxicity of the nanovector, while the hydrophilic histidine headgroup permitted enhancing the siRNA delivery potential by improving the endosomal escape via imidazole protonation. These PDA-micellar systems were fully characterized by DLS, TEM, and DOSY-NMR experiments. The resulting bioactive complexes of PDA-micelles with siRNA were shown to have an optimal size below 100 nm.

Structure Tuning of Cationic Oligospermine-siRNA Conjugates for Carrier-Free Gene Silencing.

Oligospermine-siRNA conjugates are able to induce efficient luciferase gene silencing upon carrier-free transfection. These conjugates are readily accessible by a versatile automated chemistry that we developed using a DMT-spermine phosphoramidite reagent. In this article, we used this chemistry to study a wide range of structural modifications of the oligospermine-siRNA conjugates, i.e., variation of conjugate positions and introduction of chemical modifications to increase nuclease resistance. At first we examined gene silencing activity of a series of siRNA-tris(spermine) conjugates with and without chemical modifications in standard carrier assisted conditions. The three spermine units attached at one of the two ends of the sense strand or at the 3'-end of the antisense strand are compatible with gene silencing activity whereas attachment of spermine units at the 5'-end of the antisense strand abolished the activity. 2'-O-Methylated nucleotides introduced in the sense strand are compatible while not in the antisense strand. Thiophosphate links could be used without activity loss at the 3'-end of both strands and at the 5'-end of the sense strand to conjugate oligospermine. Consequently a series of oligospermine-siRNA conjugates containing 15 to 45 spermines units in various configurations were chosen, prepared, and examined in carrier-free conditions. Attachment of 30 spermine units singly at the 5'-end of the sense strand provides the most potent carrier-free siRNA. Longevity of luciferase gene silencing was studied using oligospermine-siRNA conjugates. Five day long efficiency with more than 80% gene expression knockdown was observed upon transfection without vector. Oligospermine-siRNA conjugates targeting cell-constitutive natural lamin A/C gene were prepared. Efficient gene silencing was observed upon carrier-free transfection of siRNA conjugates containing 20 or 30 spermine residues grafted at the 5'-end of the sense strand.

From solution to in-cell study of the chemical reactivity of acid sensitive functional groups: a rational approach towards improved cleavable linkers for biospecific endosomal release.

pH-Sensitive linkers designed to undergo selective hydrolysis at acidic pH compared to physiological pH can be used for the selective release of therapeutics at their site of action. In this paper, the hydrolytic cleavage of a wide variety of molecular structures that have been reported for their use in pH-sensitive delivery systems was examined. A wide variety of hydrolytic stability profiles were found among the panel of tested chemical functionalities. Even within a structural family, a slight modification of the substitution pattern has an unsuspected outcome on the hydrolysis stability. This work led us to establish a first classification of these groups based on their reactivities at pH 5.5 and their relative hydrolysis at pH 5.5 vs. pH 7.4. From this classification, four representative chemical functions were selected and studied in-vitro. The results revealed that only the most reactive functions underwent significant lysosomal cleavage, according to flow cytometry measurements. These last results question the acid-based mechanism of action of known drug release systems and advocate for the importance of an in-depth structure-reactivity study, using a tailored methodology, for the rational design and development of bio-responsive linkers.

Synthesis of giant globular multivalent glycofullerenes as potent inhibitors in a model of Ebola virus infection.

The use of multivalent carbohydrate compounds to block cell-surface lectin receptors is a promising strategy to inhibit the entry of pathogens into cells and could lead to the discovery of novel antiviral agents. One of the main problems with this approach, however, is that it is difficult to make compounds of an adequate size and multivalency to mimic natural systems such as viruses. Hexakis adducts of [60]fullerene are useful building blocks in this regard because they maintain a globular shape at the same time as allowing control over the size and multivalency. Here we report water-soluble tridecafullerenes decorated with 120 peripheral carbohydrate subunits, so-called 'superballs', that can be synthesized efficiently from hexakis adducts of [60]fullerene in one step by using copper-catalysed azide­alkyne cycloaddition click chemistry. Infection assays show that these superballs are potent inhibitors of cell infection by an artificial Ebola virus with half-maximum inhibitory concentrations in the subnanomolar range.

Mannoside Glycolipid Conjugates Display Anti-inflammatory Activity by Inhibition of Toll-like Receptor-4 Mediated Cell Activation.

Inhibition of excessive Toll-like receptor 4 (TLR4) signaling is a therapeutic approach pursued for many inflammatory diseases. We report that Mannoside Glycolipid Conjugates (MGCs) selectively blocked TLR4-mediated activation of human monocytes and monocyte-derived dendritic cells (DCs) by lipopolysaccharide (LPS). They potently suppressed pro-inflammatory cytokine secretion and maturation of DCs exposed to LPS, leading to impaired T cell stimulation. MGCs did not interfere with LPS and could act in a delayed manner, hours after LPS stimulation. Their inhibitory action required both the sugar heads and the lipid chain, although the nature of the sugar and the structure of the lipid tail could be modified. They blocked early signaling events at the cell membrane, enhanced internalization of CD14 receptors, and prevented colocalization of CD14 and TLR4, thereby abolishing NF-κB nuclear translocation. When the best lead conjugate was tested in a mouse model of LPS-induced acute lung inflammation, it displayed an anti-inflammatory action by suppressing the recruitment of neutrophils. Thus, MGCs could serve as promising leads for the development of selective TLR4 antagonistic agents for inflammatory diseases.

Spiro Diorthoester (SpiDo), a Human Plasma Stable Acid-Sensitive Cleavable Linker for Lysosomal Release.

pH-sensitive linkers designed to undergo selective hydrolysis at acidic pH compared to physiological pH can be used for selective release of therapeutics selectively at targets and orthoesters have been demonstrated to be good candidates for such linkers. Following an HPLC screening, a Spiro Diorthoester (SpiDo) derivative was identified as a potent acid-labile group for the development of pH-sensitive targeted systems. After incorporation of this linker into activatable FRET-based probe and side-by-side comparison to a well-known alkylhydrazone linker, this SpiDo linker has shown a fast and pH sensitive hydrolysis for mild acidic conditions, a pH sensitive lysosomal hydrolysis, and high stability in human plasma.

Photopolymerized micelles of diacetylene amphiphile: physical characterization and cell delivery properties.

A series of polydiacetylene (PDA) - based micelles were prepared from diacetylenic surfactant bearing polyethylene glycol, by increasing UV-irradiation times. These polymeric lipid micelles were analyzed by physicochemical methods, electron microscopy and NMR analysis. Cellular delivery of fluorescent dye suggests that adjusting the polymerization state is vital to reach the full in vitro potential of PDA-based delivery systems.

Selective irreversible chemical tagging of cysteine with 3-arylpropiolonitriles.

Exquisite chemoselectivity for cysteine has been found for a novel class of remarkably hydrolytically stable reagents, 3-arylpropiolonitriles (APN). The efficacy of the APN-mediated tagging was benchmarked against other cysteine-selective methodologies in a model study on a series of traceable amino acid derivatives. The selectivity of the methodology was further explored on peptide mixtures obtained by trypsin digestion of lysozyme. Additionally, the superior stability of APN-cysteine conjugates in aqueous media, human plasma, and living cells makes this new thiol-click reaction a promising methodology for applications in bioconjugation.

Polycationic pillar[5]arene derivatives: interaction with DNA and biological applications.

Dendritic pillar[5]arene derivatives have been efficiently prepared by grafting dendrons with peripheral Boc-protected amine subunits onto a preconstructed pillar[5]arene scaffold. Upon cleavage of the Boc-protected groups, water-soluble pillar[5]arene derivatives with 20 (13) and 40 (14) peripheral ammonium groups have been obtained. The capability of these compounds to form stable nanoparticles with plasmid DNA has been demonstrated by gel electrophoresis, transmission electron microscopy (TEM), and dynamic light scattering (DLS) investigations. Transfection efficiencies of the self-assembled 13/pCMV-Luc and 14/pCMV-Luc polyplexes have been evaluated in vitro with HeLa cells. The transfection efficiencies found for both compounds are good, and pillar[5]arenes 13 and 14 show very low toxicity if any.

Dynamic micelles of mannoside glycolipids are more efficient than polymers for inhibiting HIV-1 trans-infection.

Mannoside glycolipid conjugates are able to inhibit human immunodeficiency virus type 1 (HIV-1) trans-infection mediated by human dendritic cells (DCs). The conjugates are formed by three building blocks: a linear or branched mannose head, a hydrophilic linker, and a 24-carbon lipid chain. We have shown that, even as single molecules, these compounds efficiently target mannose-binding lectins, such as DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN) important for HIV-1 transmission. With the goal to optimize their inhibitory activity by supramolecular structure formation, we have compared saturated and unsaturated conjugates, as single molecules, self-assemblies of dynamic micelles, and photopolymerized cross-linked polymers. Surface plasmon resonance showed that, unexpectedly, polymers of trivalent conjugates did not display a higher binding affinity for DC-SIGN than single molecules. Interactions on a chip or in solution were independent of calcium; however, binding to DCs was inhibited by a calcium chelator. Moreover, HIV-1 trans-infection was mostly inhibited by dynamic micelles and not by rigid polymers. The inhibition data revealed a clear correlation between the structure and molecular assembly of a conjugate and its biological antiviral activity. We present an interaction model between DC-SIGN and conjugates-either single molecules, micelles, or polymers-that highlights that the most effective interactions by dynamic micelles involve both mannose heads and lipid chains. Our data reveal that trivalent glycolipid conjugates display the highest microbicide potential for HIV prophylaxis, as dynamic micelles conjugates and not as rigid polymers.

Cell-penetrating cationic siRNA and lipophilic derivatives efficient at nanomolar concentrations in the presence of serum and albumin.

Despite its considerable interest in human therapy, in vivo siRNA delivery is still suffering from hurdles of vectorization. We have shown recently efficient gene silencing by non-vectorized cationic siRNA. Here, we describe the synthesis and in vitro evaluation of new amphiphilic cationic siRNA. C12-, (C12)2- and cholesteryl-spermine(x)-siRNA were capable of luciferase knockdown at nanomolar concentrations without vectorization (i.e. one to two orders of magnitude more potent than commercially available cholesteryl siRNA). Moreover, incubation in the presence of serum did not impair their efficiency. Finally, amphiphilic cationic siRNA was pre-loaded on albumin. In A549Luc cells in the presence of serum, these siRNA conjugates were highly effective and had low toxicity.

Cationic polydiacetylene micelles for gene delivery.

Cationic surfactants easily interact with plasmid DNA to form small lipoplexes. However, their detergent behavior and associated biological toxicity limit their use as gene delivery vectors. We have incorporated a diacetylene motif in the hydrophobic chain of cationic surfactants. By using UV irradiation, the small cationic micelles (9 nm) obtained with diacetylenic detergents were photopolymerized into 40 nm spheres. Electrostatic interactions with plasmid DNA led to the formation of 45 nm lipoplexes at N/P = 5 ratio. In vitro transfection of the pCMV-Luciferase plasmid resulted in gene expression (>10(10) RLU/mg protein) at the same ratio, comparable with the commercially available JetSi-ENDO gene delivery system. This new and versatile class of molecules could lead to a new generation of in vivo gene delivery vectors.

Gene delivery with polycationic fullerene hexakis-adducts.

Polyplexes prepared from DNA and globular compact polycationic derivatives constructed around a fullerene hexakis-adduct core have shown remarkable gene delivery capabilities.