Jacques Greiner

Highly fluorinated amphiphiles as drug and gene carrier and delivery systems

Abstract A short review on fluorinated liposomes made from highly fluorinated double-chain phospho- or glyco-lipids as well as fluorinated lipoplexes, e.g. complexes made from highly fluorinated polycationic lipospermines and a gene, is presented. These systems display a number of interesting physico-chemical and biological properties which make them very attractive alternatives as drug or gene carrying, targeting and delivering devices. The properties of the fluorinated liposomes that are discussed include liposome formation and shelf-stability, membrane structure, thermotropism and permeability, encapsulation, release and stability in various media (serum, detergents), bioavailability and biodistribution, anti-HIV activity. The properties of the fluorinated lipoplexes that are reported include lipoplex formation, stability, in vitro cell transfection in the presence of serum or of bile.

Carbohydrate- and related polyol-derived fluorosurfactants: an update

A short review of recent literature is presented on the synthesis, biological properties, colloid and surface chemistry, and applications of carbohydrate- and related polyol-derived amphiphiles with perfluoroalkyl hydrophobes.

Transepithelial transport of prodrugs of the HIV protease inhibitors saquinavir, indinavir, and nelfinavir across Caco-2 cell monolayers.

AbstractPurpose. This study is dedicated to the permeation of various amino acid-, D-glucose-, and PEG-conjugates of indinavir, saquinavir, and nelfinavir across monolayers of Caco-2 cells as models of the intestinal barrier. This screening is aimed at detecting the most promising prodrugs for improving the intestinal absorption of these protease inhibitors. Methods. The bidirectional transport of the prodrugs was investigated using P-gp-expressing Caco-2 monolayers grown on membrane inserts using high-performance liquid chromatography for quantitation. Results. The L-valyl, L-leucyl, and L-phenylalanyl ester conjugates led to an enhancement of the absorptive flux of indinavir or saquinavir. These results are likely attributable to an active transport mechanism and/or to a decrease of their efflux by carriers such as P-gp. Connection of tyrosine through its hydroxyl, of D-glucose, or of polyethylene glycol decreased their absorptive and secretory diffusion. Conclusions. Conjugation of the protease inhibitors to amino acids constitutes a most appealing alternative that could improve their intestinal absorption and oral bioavailability. Whether it could improve their delivery into the central nervous system remains to be explored. D-Glucose conjugation will most probably not improve their intestinal absorption or their crossing of the blood-brain barrier. If some pharmacologic benefits are to be expected from PEG-protease inhibitor conjugates, they must then be administered intravenously.

Synthesis and anti-HIV activity of glucose-containing prodrugs derived from saquinavir, indinavir and nelfinavir

With the aim at improving the transport of the current HIV protease inhibitors across the intestinal and blood brain barriers and their penetration into the central nervous system, the synthesis of various acyl and carbamatoyl glucose-containing prodrugs derived from saquinavir, indinavir and nelfinavir, their in vitro stability with respect to hydrolysis, and their anti-HIV activity have been investigated. D-Glucose, which is actively transported across these barriers, was connected through its 3-hydroxyl to these antiproteases via a linker. The liberation of the active free drug during the incubation time of the prodrugs with the cells was found to be crucial for HIV inhibition. The labile ester linking of the glucose-containing moiety to the peptidomimetic hydroxyl of saquinavir or to the indinavir C-8 hydroxyl, which is not part of the transition state isostere, is not an obstacle for anti-HIV activity. This is not the case for its stable carbamate linking to the peptidomimetic hydroxyl of saquinavir, indinavir and nelfinavir. The chemical stability with respect to hydrolysis of some of the saquinavir and indinavir prodrugs reported here, the liberation rate of the active free drug and the HIV inhibitory potency are acceptable for an in vivo use of these prodrugs. These glucose-linked ester and carbamate prodrugs display a promising therapeutic potential provided that their bioavailability, penetration into the HIV sanctuaries, and/or the liberation of the active free drug from the carbamate prodrugs are improved. Furthermore, no cytotoxicity was detected for the prodrugs for concentrations as high as 10 or even 100 microM, thus indicating an encouraging therapeutic index.

Synthesis of double-tailed (perfluoroalkyl)alkyl phosphosugars: new components for drug-carrying and -targeting systems

Abstract Double-tailed d -glycose 3- and 6-[sodium (perfluoroalkyl)alkyl phosphates] were synthesized via the hydrogen phosphonate approach. Stable double-tailed (perfluoroalkyl)alkyl hydrogenphosphonates, prepared from double-tailed (perfluoroalkyl)alkanols and PCl 3 -imidazole, reacted with 1,2:3,4-di- O -isopropylidene-α- d -galactopyranose or with 1,2:5,6 -di- O -isopropylidene-α- d -glucofuranose in the presence of Me 3 CCOCl as the condensing agent to give, after oxidation with aqueous iodine, the corresponding O -protected glycose phosphate diesters. O -Deisopropylidenation of the latter by aqueous trifluoroacetic acid afforded the target compound in 70% yield, based on the protected glycosides. Condensation of 1,2,3,4-tetra- O -acetyl-β- d -glucopyranose or -mannopyranose with double-tailed (perfluoroalkyl)alkyl hydrogenphosphonates or 10-eicosyl hydrogenphosphonate, via the coupling and oxidation steps described above, afforded per- O -acetylglycose phosphodiesters. O -Deacetylation with MeONa-MeOH was achieved in 65% yield based on the protected sugar. All the compounds were characterized by 19 F, 1 H, 13 C, and 31 P NMR data. Preliminary biocompatibility assays indicate a reduction of hemolytic activity when fluorinated chains are present and maximum tolerated doses of ca. 125 mg/kg body weight in mice.

Synthesis of single- and double-chain fluorocarbon and hydrocarbon galactosyl amphiphiles and their anti-HIV-1 activity

Galactosylceramide (GalCer) is an alternative receptor allowing HIV-1 entry into CD4(-)/GalCer(+) cells. This glycosphingolipid recognizes the V3 loop of HIV gp120, which plays a key role in the fusion of the HIV envelope and cellular membrane. To inhibit HIV uptake and infection, we designed and synthesized analogs of GalCer. These amphiphiles and bolaamphiphiles consist of single and double hydrocarbon and/or fluorocarbon chain beta-linked to galactose and galactosamine. They derive from serine (GalSer), cysteine (GalCys), and ethanolamine (GalAE). The anti-HIV activity and cytotoxicity of these galactolipids were evaluated in vitro on CEM-SS (a CD4(+) cell line), HT-29, a CD4(-) cell line expressing high levels of GalCer receptor, and/or HT29 genetically modified to express CD4. GalSer and GalAE derivatives, tested in aqueous medium or as part of liposome preparation, showed moderate anti-HIV-1 activities (IC50 in the 20-220 microM range), whereas none of the GalCys derivatives was found to be active. Moreover, only some of these anti-HIV active analogs inhibited the binding of [3H]suramin (a polysulfonyl compound which displays a high affinity for the V3 loop) to SPC3, a synthetic peptide which contains the conserved GPGRAF region of the V3 loop. Our results most likely indicate that the neutralization of the virion through masking of this conserved V3 loop region is not the only mechanism involved in the HIV-1 antiviral activity of our GalCer analogs.

Phase behavior of fluorocarbon and hydrocarbon double-chain hydroxylated and galactosylated amphiphiles and bolaamphiphiles. Long-term shelf-stability of their liposomes.

This paper describes the morphological characterization, by freeze-fracture electron microscopy, and the thermotropic phase behavior, by differential scanning calorimetry and/or X-ray scattering, of aqueous dispersions of various hydroxylated and galactosylated double-chain amphiphiles and bolaamphiphiles, several of them containing one or two hydrophobic fluorocarbon chains. Colloidal systems are observed in water with the hydroxylated hydrocarbon or fluorocarbon bolaamphiphiles only when they are dispersed with a co-amphiphile such as rac-1,2-dimyristoylphosphatidylcholine (DMPC) or rac-1,2-distearoylphosphatidylcholine (DSPC). Liposomes are formed providing the relative content of bolaamphiphiles does not exceed 20% mol. Most of these liposomes can be thermally sterilized and stored at room temperature for several months without any significant modification of their size and size distribution. The hydrocarbon galactosylated bolaamphiphile HO[C24][C12]Gal forms in water a lamellar phase (the gel to liquid-crystal phase transition is complete at 45 degrees C) and a Im3m cubic phase above 47 degrees C. The fluorocarbon HO[C24][F6C5]Gal analog displays a more complex and metastable phase behavior. The fluorinated non-bolaform galactosylated [F8C7][C16]AEGal and SerGal amphiphiles form lamellar phases in water. Low amounts (10% molar ratio) of the HO[C24][F6C5]Gal or HO[C24][C12]Gal bolaamphiphiles or of the single-headed [F8C7][C16]AEGal improve substantially the shelf-stability of reference phospholipon/cholesterol 2/1 liposomes. These liposomes when co-formulated with a single-headed amphiphile from the SerGal series are by far less stable.

Addition of perfluoroalkyl iodides to 4-pentenol and its derivatives: one-pot preparation of 2-[(F-alkyl)methyl]tetrahydrofurans

Abstract Depending on the nature of the alkaline medium, the radical addition of perfluoroalkyl iodides to 4-pentenol gives a mixture of 5-( F -alkyl)-4-pentenol and 2-[( F -alkyl)- methyl]tetrahydrofuran, or the latter alone.

synthesis of single- and double-chain fluorocarbon and hydrocarbon β-linked galactose amphiphiles derived from serine

Abstract Single- and double-chain β-linked galactose amphiphiles derived from serine were synthesized. Both types of compounds have potential as material for the formulation of liposomal drug carrier and targeting systems and as HIV inhibitors.

Quinolone-based drugs against Toxoplasma gondii and Plasmodium spp.

Owing to the rapid emergence of multi-resistant strains of Plasmodium spp. (the causative agents of malaria) and the limitations of drugs used against Toxoplasma gondii (an important opportunistic pathogen associated with AIDS and congenital birth defects), the discovery of new therapeutical targets and the development of new drugs are needed. The presence of the prokaryotic-like organelle in apicomplexan parasites (i.e. plastids), which comprise these major human pathogens, may represent a unique target for antibiotics against these protozoa. Quinolones which are known to be highly potent against bacteria were also found to specifically disrupt these parasites. They inhibit DNA replication by interacting with two essential bacterial type II topoisomerases, DNA gyrase and topoisomerase IV. There are some clues that quinolones act on plastids with a similar mechanism of action. After a brief presentation of plasmodium and toxoplasma dedicated to their life cycle, the chemotherapies presently used in clinics to fight against these protozoa and the potential new targets and drugs, we will focus our attention on their plastid which is one of these promising new targets. Then, we will present the various drugs and generations of quinolones, the leading molecules, and their inhibitory effects against these parasites together with their pharmacological properties that have been established from in vitro and in vivo studies. We will also discuss their possible mode of action.