Glutathione PEGylated liposomal methylprednisolone (2B3-201) attenuates CNS inflammation and degeneration in murine myelin oligodendrocyte glycoprotein induced experimental autoimmune encephalomyelitis.

Methylprednisolone (MP) pulses are the mainstay for relapse therapy in multiple sclerosis (MS). To improve the efficacy of treatment and reduce the side effects of MP, a long circulating brain-targeted formulation was developed; glutathione polyethylene glycol (PEG)ylated liposomal MP (2B3-201). Here we investigate the efficacy of 2B3-201 in murine myelin oligodendrocyte induced experimental autoimmune encephalomyelitis (MOG-EAE), an animal model mimicking inflammatory features and neurodegenerative aspects of MS. After disease onset, mice were randomized to receive either saline, three injections of free MP (high dose MP, 100mg/kg i.v.), two injections of free MP (low dose MP, 10mg/kg; i.v.), or two injections of 2B3-201 (10mg/kg i.v.). Treatment with a low dose of 2B3-201 significantly reduced the severity of EAE as compared to saline control, similar to treatment with high dose free MP, while a low dose of free MP was not effective. In a histological analysis of the spinal cord, treatment with 2B3-201 significantly decreased T cell as well as macrophage/microglia infiltration in the CNS by about 50%. Moreover, application of a low dose of 2B3-201 or a high dose of free MP reduced the amount of astrocyte activation as well as the extent of axonal loss and also demyelination in spinal cord lesions as compared to low dose MP or sham treatment. In summary, in the murine MOG-EAE model of MS, a glutathione PEGylated liposomal formulation of MP (2B3-201) is clinically and histologically as effective as free MP at one tenth of the dosage as well as at a lower application frequency and clearly more effective than the same dosage of free MP. These positive proof-of-concept efficacy studies warrant further development of 2B3-201 for the treatment of neuroinflammatory conditions such as MS.

Systemic treatment with glutathione PEGylated liposomal methylprednisolone (2B3-201) improves therapeutic efficacy in a model of ocular inflammation.

PURPOSE: Ocular inflammation is associated with the loss of visual acuity and subsequent blindness. Since their development, glucocorticoids have been the mainstay of therapy for ocular inflammatory diseases. However, the clinical benefit is limited by side effects due to the chronic use and generally high dosage that is required for effective treatment. We have developed the G-Technology to provide a means for sustained drug delivery, increased drug half-life, and reduced bodily drug exposure. Glutathione PEGylated liposomal methylprednisolone (2B3-201) has been developed as treatment for neuroinflammatory conditions and was evaluated in ocular inflammation. METHODS: The efficacy of 2B3-201 was investigated in rats with experimental autoimmune uveitis (EAU). Rats received 10 mg/kg of 2B3-201 intravenously at disease onset and at peak of the disease. The same dose of free methylprednisolone served as control treatment. Clinical signs of ocular inflammation were assessed by slit-lamp and immunohistochemistry. RESULTS: Whereas free methylprednisolone was ineffective, two doses of 2B3-201 almost completely abolished clinical signs of EAU. This was corroborated further by immunohistochemical analyses of isolated eyes. Treatment with 2B3-201 significantly reduced the infiltration of inflammatory cells and subsequent destruction of the retina cell layers. CONCLUSIONS: In this study, we show that systemic treatment with 2B3-201, a glutathione PEGylated liposomal methylprednisolone formulation, resulted in a superior efficacy in rats with EAU. Altogether, our findings hold promise for the development of a safe and more convenient systemic treatment for uveitis.

Pharmacokinetics, brain delivery, and efficacy in brain tumor-bearing mice of glutathione pegylated liposomal doxorubicin (2B3-101).

Brain cancer is a devastating disease affecting many people worldwide. Effective treatment with chemotherapeutics is limited due to the presence of the blood-brain barrier (BBB) that tightly regulates the diffusion of endogenous molecules but also xenobiotics. Glutathione pegylated liposomal doxorubicin (2B3-101) is being developed as a new treatment option for patients with brain cancer. It is based on already marketed pegylated liposomal doxorubicin (Doxil®/Caelyx®), with an additional glutathione coating that safely enhances drug delivery across the BBB. Uptake of 2B3-101 by human brain capillary endothelial cells in vitro was time-, concentration- and temperature-dependent, while pegylated liposomal doxorubicin mainly remained bound to the cells. In vivo, 2B3-101 and pegylated liposomal doxorubicin had a comparable plasma exposure in mice, yet brain retention 4 days after administration was higher for 2B3-101. 2B3-101 was overall well tolerated by athymic FVB mice with experimental human glioblastoma (luciferase transfected U87MG). In 2 independent experiments a strong inhibition of brain tumor growth was observed for 2B3-101 as measured by bioluminescence intensity. The effect of weekly administration of 5 mg/kg 2B3-101 was more pronounced compared to pegylated liposomal doxorubicin (p<0.05) and saline (p<0.01). Two out of 9 animals receiving 2B3-101 showed a complete tumor regression. Twice-weekly injections of 5 mg/kg 2B3-101 again had a significant effect in inhibiting brain tumor growth (p<0.001) compared to pegylated liposomal doxorubicin and saline, and a complete regression was observed in 1 animal treated with 2B3-101. In addition, twice-weekly dosing of 2B3-101 significantly increased the median survival time by 38.5% (p<0.001) and 16.1% (p<0.05) compared to saline and pegylated liposomal doxorubicin, respectively. Overall, these data demonstrate that glutathione pegylated liposomal doxorubicin enhances the effective delivery of doxorubicin to brain tumors and could become a promising new therapeutic option for the treatment of brain malignancies.

Targeted blood-to-brain drug delivery --10 key development criteria.

Drug delivery to the brain remains challenging due to the presence of the blood-brain barrier. In this review, 10 key development criteria are presented that are important for successful drug development to treat CNS diseases by targeted drug delivery systems. Although several routes of delivery are being investigated, such as intranasal delivery, direct injections into the brain or CSF, and transient opening of the blood-brain barrier, the focus of this review is on physiological strategies aiming to target endogenous transport mechanisms. Examples from literature, focusing on targeted drug delivery systems that are being commercially developed, will be discussed to illustrate the 10 key development criteria. The first four criteria apply to the targeting of the blood-brain barrier: (1) a proven inherently safe receptor biology, (2) a safe and human applicable ligand, (3) receptor specific binding, and (4) applicable for acute and chronic indications. Next to an efficient and safe targeting strategy, as captured in key criteria 1 to 4, a favorable pharmacokinetic profile is also important (key criterion 5). With regard to the drug carriers, two criteria are important: (6) no modification of active ingredient and (7) able to carry various classes of molecules. The final three criteria apply to the development of a drug from lab to clinic: (8) low costs and straightforward manufacturing, (9) activity in all animal models, and (10) strong intellectual property (IP) protection. Adhering to these 10 key development criteria will allow for a successful brain drug development.

Enhanced brain delivery of liposomal methylprednisolone improved therapeutic efficacy in a model of neuroinflammation.

Neuroinflammation contributes to a wide range of disorders of the central nervous system (CNS). Of the available anti-inflammatory drugs, only glucocorticoids have shown central efficacy in CNS-related disorders, such as multiple sclerosis (MS). However, their side effects are dose limiting. To optimally improve the therapeutic window of methylprednisolone, we enhanced its CNS delivery by using pegylated liposomes conjugated to the brain-targeting ligand glutathione. In healthy rats, plasma circulation and brain uptake were significantly increased after encapsulating methylprednisolone in glutathione pegylated (GSH-PEG) liposomes. Furthermore, the efficacy of GSH-PEG liposomal methylprednisolone was investigated in rats with acute experimental autoimmune encephalomyelitis (EAE), an animal model of MS; rats received treatment (10mg/kg; i.v. injection), before disease onset, at disease onset, or at the peak of disease. Free methylprednisolone and non-targeted pegylated (PEG) liposomal methylprednisolone served as control treatments. When treatment was initiated at disease onset, free methylprednisolone showed no effect, while GSH-PEG liposomal methylprednisolone significantly reduced the clinical signs to 42±6.4% of saline control. Moreover, treatment using GSH-PEG liposomes was significantly more effective compared to PEG liposomes. Our findings hold promise for MS treatment and warrant further investigations into this brain delivery system for the treatment of neuroinflammation.

Targeted CRM197-PEG-PEI/siRNA Complexes for Therapeutic RNAi in Glioblastoma.

RNA interference (RNAi) allows the specific knockdown of tumor relevant genes. To induce RNAi, the delivery of small interfering RNAs (siRNAs) is of crucial importance. This is particularly challenging for their therapeutic applications in vivo. Low molecular weight branched polyethylenimine (PEI) is safe and efficient for nucleic acid delivery including small RNA molecules, based on its ability to electrostatically complex siRNA molecules, thereby protecting them from nuclease degradation. The nanoscale PEI/siRNA complexes are endocytosed by cells prior to intracellular complex release from the lysosome and cytoplasmic release of the siRNAs from the complexes. Chemical modification and ligand decoration of the complexes aim at introducing target tissue specificity and further increased efficacy of PEI-mediated siRNA delivery. CRM197 is a mutated, non-toxic diphtheria toxin (DT) that binds to the membrane-bound precursor of HB-EGF-like growth factor/diphtheria toxin receptor highly expressed in glioblastoma cells. Likewise, the growth factor pleiotrophin (PTN/HB-GAM/HARP) is overexpressed in glioblastoma and is rate limiting for tumor growth, thus representing an attractive target gene for therapeutic knockdown approaches. PEGylation of PEI was performed to reduce the surface charge, and by CRM197 coupling we prepared a modified PEI for siRNA delivery into glioblastoma cells. The novel PEI conjugates were analyzed for their complexation efficiency and optimal mixing ratios, and complexes were physicochemically characterized regarding stability, size and zeta potential. The biological activity of the complexes was confirmed in cell culture by reporter gene knockdown. For the therapeutic treatment of subcutaneous human gliobastoma xenografts in athymic nude mice, we systemically injected the modified PEI/siRNA complexes targeting PTN. Antitumor effects based on PTN knockdown demonstrated the advantage of tumor-targeted CRM197-PEG-PEI/siRNA over untargeted PEG-PEI polyplexes. Thus, we establish targeted CRM197-PEG-PEI-based complexes for siRNA delivery in vivo, and show therapeutic effects of CRM197-PEG-PEI/siRNA-mediated knockdown of PTN.

Efficient degradation-aided selection of protease inhibitors by phage display.

In this report, we describe a novel phage display strategy for the identification of dedicated protease inhibiting peptides, based on degradation-aided enrichment of protease resistant phages. Phages were directly incubated with a range of phage-degrading proteases, after which non-degraded phages were used for the next selection round. For proteinase-K we identified after only four selection rounds a peptide (VLIMPVLLGIPLLC) that inhibits proteinase-K activity with an inhibition constant of 4 microM. In analogy, we identified a peptide capable of inhibiting substrate degradation by cathepsin-S (VWNCERITISRLIN), which showed functional inhibition of cathepsin-S induced sprouting of endothelial cells. We envision that the pursued strategy of degradation-aided selection of protease inhibitors (DASPI) represents an effective approach in the design of new protease inhibitors but also of new strategies to render gene and drug vectors protease resistant.

Gallic acid antagonizes P-selectin-mediated platelet-leukocyte interactions: implications for the French paradox.

BACKGROUND: Current paradigm attributes the low incidence of cardiovascular disorders in Mediterranean countries despite a high saturated fat intake, the "French paradox," to the antioxidant capacity of red wine polyphenols. Conceivably, other antiinflammatory pathways may contribute to at least a similar extent to the atheroprotective activity of these polyphenols. We have investigated whether gallic acid (GA), an abundant red wine polyphenol, modulates the activity of P-selectin, an adhesion molecule that is critically involved in the recruitment of inflammatory cells to the vessel wall and thus in atherosclerosis. METHODS AND RESULTS: GA potently inhibited the binding of a peptide antagonist (IC50, 7.2 micromol/L) and biotin-PAA-Le(a)-SO3H, an established high-affinity ligand, to P-selectin (IC50, 85 micromol/L). Under dynamic flow conditions, GA markedly and dose dependently attenuated the rolling of monocytic HL60 cells over P-selectin-transfected Chinese hamster ovary cells (EC50, 14.5 micromol/L) while increasing the velocity of P-selectin-dependent rolling of human blood leukocytes over a platelet monolayer. In vivo tests established that GA administration to normolipidemic C57/Bl6 and aged atherosclerotic apolipoprotein E-deficient mice impaired the baseline rolling of conjugates between activated platelets and circulating monocytes over femoral vein endothelium, as judged by online video microscopy (ED50, 1.7+/-0.3 and 1.5+/-0.4 mg x kg(-1) x h(-1), respectively). CONCLUSIONS: Our findings provide a solid mechanistic foundation through which GA intervenes in major inflammatory pathobiologies by binding and antagonizing P-selectin.

Inhibition of Streptococcus suis adhesion by dendritic galabiose compounds at low nanomolar concentration.

A series of mono-, di-, and tetravalent galabiose (Galalpha1-4Gal) compounds were synthesized in good yields by coupling of a general carboxylic acid-bearing sugar building block to dendritic scaffolds based on the 3,5-di-(2-aminoethoxy)benzoic acid branching unit. Furthermore, a poly(amidoamine)- (PAMAM-) based dendritic galabioside was synthesized containing eight galabiose units. All galabiosides were tested in a hemagglutination assay and a surface plasmon resonance (SPR) competition assay in order to establish their potency in the binding to the bacterial Gram-positive pathogen Streptococcus suis. A monovalent galabioside containing a short spacer was used as a reference compound in all the assays. Variations in the scaffold as well as in the spacer arms were introduced to determine their influence on the inhibition. The best inhibitor of hemagglutination was an octavalent galabioside with a minimal inhibitory concentration (MIC) of 0.3 nM, to the best of our knowledge the first example of inhibition of bacterial binding by a soluble carbohydrate at a subnanomolar concentration.

Blocking endothelial adhesion molecules: a potential therapeutic strategy to combat atherogenesis.

PURPOSE OF REVIEW: This review provides a concise update of the involvement of endothelial adhesion molecules in atherogenesis, an overview of current advances in the development of adhesion molecule blocking agents, as well as an insight into the potential of these molecules in cardiovascular therapy. RECENT FINDINGS: As endothelial adhesion molecules are deemed to play an important role in the development and progression of atherosclerotic lesions, they are interesting targets for therapeutic intervention in this process. In particular, P-selectin and vascular cell adhesion molecule 1 are widely considered to hold promise in this regard. Current research efforts centre on the design of agents that directly block the interaction of the receptor with its ligand (e.g. soluble P-selectin glycoprotein ligand 1, blocking antibodies, EWVD-based peptides) or that interfere with their synthesis (e.g. antisense oligonucleotides) or their regulatory control by nuclear factor kappa B or peroxisome proliferator-activated receptor gamma. Furthermore, adhesion molecules have been exploited as a target for the specific delivery of drug carriers (e.g. biodegradable particles with entrapped dexamethasone) or therapeutic compounds (e.g. dexamethasone) to the plaque. All approaches have been shown to be effective in blocking adhesion molecule function in in-vitro studies and in-vivo models for inflammation or atherosclerosis. SUMMARY: Although the field has achieved considerable progress in recent years, leading to the development of a number of interesting leads, final proof of their efficacy in cardiovascular therapy is eagerly awaited.

Rational optimization of a short human P-selectin-binding peptide leads to nanomolar affinity antagonists.

P-selectin plays an important role in the development of various diseases, including atherosclerosis and thrombosis. In our laboratory we recently identified a number of specific human P-selectin-binding peptides containing a Glu-Trp-Val-Asp-Val consensus motif, displaying a low micromolar affinity for P-selectin (IC(50) = 2 microm). In search of more potent antagonists for P-selectin, we have optimized the EWVDV pentapeptide core motif via a two-step combinatorial chemistry approach. A dedicated library of peptide derivatives was generated by introducing seven substituents at the N and C termini of the motif. In particular, pentapeptides with gallic acid or 1,3,5-benzenetricarboxylic acid substituents at the N terminus proved to be considerably more potent inhibitors of P-selectin binding than the parental peptide. After removal of the N-terminal glutamic acid from the core sequence, which appeared to be replaceable by a carboxamide function without loss of affinity, a second library was synthesized to map the chemical moieties within the gallic acid or 1,3,5-benzenetricarboxyl acid groups responsible for the enhanced P-selectin binding. Moreover, by varying the length and rigidity of the connective spacer, we have further optimized the spatial orientation of the N-terminal substituent. The combined use of phage display and subsequent combinatorial chemistry led to the design of a number of gallic acid- containing peptides with low nanomolar affinity for P-selectin both under static and dynamic conditions (IC(50) = 15.4 nm). These small synthetic antagonists, which are equally as potent as the natural ligand P-selectin glycoprotein ligand-1, are promising leads in anti-atherothrombotic therapy.

Specific inhibition of P-selectin-mediated cell adhesion by phage display-derived peptide antagonists.

P-selectin is a leukocyte adhesion receptor expressed on activated vascular endothelium and platelets that mediates leukocyte rolling and attachment. Because P-selectin is critically involved in inflammation, we used phage display libraries to identify P-selectin-specific peptides that might interfere with its proinflammatory function. Isolated phage contained a highly conserved amino acid motif. Synthetic peptides showed calcium-dependent binding to P-selectin, with high selectivity over E-selectin and L-selectin. The peptides completely antagonized adhesion of monocyte-derived HL60 cells to P-selectin and increased their rolling velocities in flow chamber experiments. Peptide truncation and alanine-scanning studies indicated that an EWVDV (single-letter amino acid codes) consensus motif sufficed for effective inhibition. Intriguingly, the apparent avidity of the peptides was increased 200-fold when presented in a tetrameric form (2 microM versus 10 nM), which is consistent with the proposed divalent interaction of P-selectin glycoprotein ligand 1 (PSGL-1) with P-selectin. As the EWVDV peptides inhibit the binding of an established glycoside ligand for P-selectin (sulfated Lewis A), it is conceivable that EWVDV interacts with or in close proximity to the actual carbohydrate recognition domain of P-selectin, without being a direct structural mimic of sialyl Lewis(x). These ligands are among the most potent antagonists of P-selectin yet designed. Their high affinity, selectivity, and accessible synthesis provide a promising entry to the development of new anti-inflammatory therapeutics and might be a powerful tool to provide important information on the binding site of P-selectin.