Targeting of daunomycin using biotinylated immunoliposomes: pharmacokinetics, tissue distribution and in vitro pharmacological effects.

Biotinylated immunoliposomes were prepared by a non-covalent (biotin-streptavidin) coupling procedure and conjugated to the OX26 monoclonal antibody directed against the rat transferrin receptor. In vitro, these biotinylated immunoliposomes were used to by-pass P-glycoprotein in multidrug-resistant RBE4 brain capillary endothelial cells and thereby to achieve 2- to 3-fold higher intracellular accumulation of liposomal daunomycin as compared to free drug. The extent of cellular uptake of liposomal daunomycin was dose- and time-dependent, was inhibited by competition with unbound OX26 and was associated with a pharmacological (i.e. cytotoxic) effect. Cytotoxic effects of liposomal formulations of daunomycin, in contrast to the free drug, were apparent only after prolonged incubation periods being indicative of a slow intracellular unpacking and release of liposomal daunomycin. Pharmacokinetics and tissue distribution studies in the rat revealed brain accumulation of daunomycin in OX26-immunoliposomes to higher levels as compared to brain uptake of free daunomycin, or daunomycin incorporated within pegylated liposomes or within unspecific IgG(2a) isotype control immunoliposomes. Such OX26-mediated effects were not observed in other tissues such as spleen, liver, muscle or kidney.

Drug transport to brain with targeted liposomes.

Antibody-conjugated liposomes or immunoliposomes are particulate drug carriers that can be used to direct encapsulated drug molecules to diseased tissues or organs. The present review discusses examples of successful applications of this technology to achieve drug transport across the blood-brain barrier. In addition, information will be provided on practical aspects such as phospholipid compositions of liposomes, antibody coupling technologies, large-scale production of liposomes, and obstacles related to drug loading of the carrier. Prospects of future uses of immunoliposome-based drug delivery systems such as gene therapy of the brain and clinical trials are discussed.

Targeting of skeletal muscle in vitro using biotinylated immunoliposomes.

In the present study, a non-covalent (biotin-streptavidin) coupling procedure for the preparation of pegylated immunoliposomes is presented, which simplifies the attachment of targeting vectors to sterically stabilized liposomes. A biotinylated poly(ethylene glycol) (PEG)-phospholipid [bio-PEG-distearoylphosphatidylethanolamine (DSPE)] was used as a linker between a streptavidin-conjugated monoclonal antibody (mAb) (i.e. the OX26 mAb raised against the rat transferrin receptor) and 150 nm liposomes. OX26-streptavidin had a biotin binding capacity of two to three biotin molecules per OX26-streptavidin conjugate. Immunostaining experiments with the OX26 mAb followed by fluorescent confocal microscopy revealed immunofluorescence labelling of the transferrin receptor on skeletal muscle, as well as in L6 cells, a continuous cell line derived from rat skeletal muscle. Uptake experiments with L6 cells using the OX26 mAb, fluorescence-labelled OX26-streptavidin or fluorescent OX26-immunoliposomes demonstrated cellular uptake and accumulation within an intracellular compartment of the OX26 mAb and its conjugates. Cellular uptake of OX26 conjugates was sensitive to competition with free OX26 antibody. In summary, these studies describe the design of biotinylated immunoliposomes as a universal drug transport vector and their potential for targeting of the transferrin receptor of skeletal muscle.

No stirring necessary: parallel carbonylation of aryl halides with CO and various alcohols under pressure.

The parallel carbonylation of aryl halides with 6-25 bar of CO in 1-mL vials in a standard autoclave was investigated. 4-Bromoacetophenone and 2-chloropyridine were used as model substrates with 102 different O-nucleophiles (primary and secondary alcohols, phenols). No inertization during the loading was necessary. Fifty esters (43 new, yield up to 60%) were isolated and characterized. Ether, ester, ketone, and sometimes even olefin functions were usually tolerated. The new method is suitable for screening and small scale products synthesis.

Synthesis of unsymmetrical aroyl acyl imides by aminocarbonylation of aryl bromides.

Aroyl imides were prepared by a palladium-catalyzed aminocarbonylation reaction of aryl bromides with carbon monoxide and primary amides in good yields (58-72%). The reactions were carried out under mild conditions (5 bar, 120 degrees C) using 1 mol % of a palladium phosphine complex. Several aryl bromides were reacted with formamide, acetamide, benzamide, and benzenesulfonamide, respectively. For activated aryl bromides, a phosphine-to-palladium ratio of 2:1 was sufficient, but less reactive aryl bromides required a ligand-to-palladium ratio of 6:1 in order to stabilize the catalyst and achieve full conversion. The imides were very sensitive to aqueous basic conditions and were easily converted to aroyl amides or benzoic acids.