Olena Sivak

Discovery and Development of Toll-Like Receptor 4 (TLR4) Antagonists: A New Paradigm for Treating Sepsis and Other Diseases

AbstractSepsis remains the most common cause of death in intensive care units in the USA, with a current estimate of at least 750,000 cases per year, and 215,000 deaths annually. Despite extensive research still we do not quite understand the cellular and molecular mechanisms that are involved in triggering and propagation of septic injury. Endotoxin (lipopolysaccharide from Gram-negative bacteria, or LPS) has been implicated as a major cause of this syndrome. Inflammatory shock as a consequence of LPS release remains a serious clinical concern. In humans, inflammatory responses to LPS result in the release of cytokines and other cell mediators from monocytes and macrophages, which can cause fever, shock, organ failure and death. A number of different approaches have been investigated to try to treat and/or prevent the septic shock associated with infections caused by Gram-negative bacteria, including blockage of one or more of the cytokines induced by LPS. Recently several novel amphipathic compounds have been developed as direct LPS antagonists at the LPS receptor, TLR4. This review article will outline the current knowledge on the TLR4-LPS synthesis and discuss the signaling, in vitro pre-clinical and in vivo clinical evaluation of TLR4 antagonists and their potential use in sepsis and a variety of diseases such as atherosclerosis as well as hepatic and renal malfunction.

Development and characterization of oral lipid-based amphotericin B formulations with enhanced drug solubility, stability and antifungal activity in rats infected with Aspergillus fumigatus or Candida albicans.

OBJECTIVE To develop an oral formulation of Amphotericin B (AmpB) with: (A) medium chain triglycerides, fatty acids and nonionic surfactants as a self-emulsifying drug delivery system (SEDDS); or (B) glyceryl mono-oleate (Peceol) with poly(ethylene glycol) (PEG)-phospholipids. METHODS SEDDS formulations were prepared by simple mixing at 40 degrees C. Peceol/DSPE-PEG-lipid formulations were prepared by solvent evaporation. Parameters evaluated included: miscibility, solubility and emulsion droplet size after incubation in simulated gastric fluid (SGF) or simulated intestinal fluid (SIF) via dynamic light scattering. The stability of AmpB in Peceol/DSPE-PEG was evaluated in SGF and SIF. Phase stability of AmpB in Peceol+/-DSPE-PEG following thermal cycling was evaluated by atomic force microscopy (AFM). Aspergillus fumigatus (2.9-3.45 x 10(7) colony forming units per mL [CFU]) or Candida albicans (3-3.65 x 10(6) CFU per mL) were injected via the jugular vein; 48 h later male albino Sprague-Dawley rats (350-400 g) were administered either a single oral gavage of a Peceol-DSPE/PEG2000-based AmpB (10 mg AmpB/kg and 5 mg AmpB/kg for the Candida albicans study only) twice daily for 2 consecutive days, a single intravenous (i.v.) dose of Abelcet (5mg AmpB/kg), or physiologic saline (non-treated controls; n=9) once daily for 2 consecutive days. Antifungal activity was assessed by organ CFU concentrations and plasma galactomannan levels in the case of A. fumigatus and organ CFU concentrations in the case of Candida albicans. Plasma samples were taken from each animal prior to infection, 48 h after initiation of infection but prior to drug treatment and at the end of the study for plasma creatinine determinations as a measure of renal toxicity. RESULTS Mean diameter of SEDDS after 30 min in 150 mM NaCl at 37 degrees C was 200-400 nm. However, the Peceol/DSPE-PEG, where PEG MW was 350, 550, 750 or 2000, showed a greater solubilization of AmpB (5 mg/mL) compared to SEDDS formulations (100-500 microg/mL). Upon dispersion in SIF, Peceol/DSPE-PEG formulations generated submicron emulsion particle sizes varying slightly with PEG MW. Stability of the AmpB in Peceol/DSPE-PEG formulations in SGF or SIF was >80% after 2 h, and best for formulations containing DSPE-PEG 750 or 2000 compared to 350, 550 or Peceol only. Monoglyceride-Peceol-DSPE/PEG2000-based oral AmpB treatment significantly decreased total fungal CFU concentrations recovered in all the organs added together by >80% compared to non-treated controls without significant changes in plasma creatinine levels in the A. fumigatus infected rats. In addition, this formulation significantly decreased kidney fungal CFU concentrations by >75% at the 5 mg/kg dose and by >95% at the 10 mg/kg dose compared to non-treated controls without significant changes in the plasma creatinine levels in the Candida albicans-infected rats. CONCLUSIONS Novel lipid-based AmpB oral formulations were prepared that provide excellent drug solubilization, drug stability in simulated gastric and intestinal fluids and antifungal activity without renal toxicity in rats infected with A. fumigatus and C. albicans.

Pharmacokinetics and biodistribution of amphotericin B in rats following oral administration in a novel lipid-based formulation

OBJECTIVES To assess the pharmacokinetics and biodistribution of amphotericin B (AmB) following oral administration in a novel mono/diglyceride-phospholipid formulation and to compare with intravenous (iv) administrations using commercial formulations. METHODS Rats were allocated into the following treatment groups: oral gavage of AmB dispersed in mono/diglyceride-phospholipid formulation at doses of 4.5 and 10 mg/kg; iv bolus administration of 0.8 mg/kg Fungizone; iv bolus of 5 mg/kg Abelcet and iv bolus of 5 mg/kg AmBisome. Blood was sampled from jugular vein cannula at certain time points. The animals were sacrificed 72 h following administration of AmB and multiple tissues were harvested. The concentration of AmB in plasma and tissues was determined by means of HPLC. The plasma creatinine concentrations were determined using an enzymatic kit. RESULTS The pharmacokinetics and tissue distribution of AmB following iv administrations of the commercial formulations were found to be highly formulation dependent. The terminal half-life and biodistribution of orally administered AmB in a mono/diglyceride-phospholipid formulation resembled those of Fungizone. The larger volume of the co-administered lipid-based formulation in the case of the higher dose of orally administered AmB resulted in flip-flop kinetics and in preferential distribution into the kidneys. No nephrotoxicity was detected for any formulation and route of administration. CONCLUSIONS Oral administration of AmB in a mono/diglyceride-phospholipid formulation to rats resulted in significant intestinal absorption into the systemic circulation with pharmacokinetic and biodistribution properties similar to a micellar iv preparation.

Long-circulating non-toxic blood pool imaging agent based on hyperbranched polyglycerols

PURPOSE Currently, in vivo or in vitro(99m)Tc-radiolabelled red blood cells are the standard blood pool imaging agents. Due to risks associated with handling of blood and the problems with the current (99m)Tc shortage, we were interested in a long-circulating biocompatible synthetic macromolecule that would be simple to prepare and could also be used for PET imaging. METHODS A high molecular weight hyperbranched polyglycerol (HPG) of 500 kDa was derivatized to coordinate radioactive gallium and to establish its labelling efficiency, stability and pharmacokinetics. RESULTS The resulting radiopharmaceutical in kit form was labelled rapidly within a couple of minutes at room temperature, was stable in transferrin and EDTA challenge tests, and was non-toxic in both cell viability and different hemocompatibility assays. A pharmacokinetic biodistribution study showed that the (67)Ga-HPGN was confined to the blood compartment with a biological half life of 50.7h. CONCLUSION (67)Ga-HPGN is thus a simple to prepare blood pool imaging agent for applications where a long biological half-life is essential, i.e., the diagnosis of internal bleeding. Since radiolabelling of the same kit with (68)Ga was also confirmed, we plan to evaluate it shortly as a PET blood pool imaging agent for cardiac applications.

Tropically stable novel oral lipid formulation of amphotericin B (iCo-010): biodistribution and toxicity in a mouse model

BackgroundThe purpose of this study was to evaluate the biodistribution and toxicity of amphotericin B (AmB) following multiple oral administrations of a novel tropically stable lipid-based formulation (iCo-010).MethodsBALB/c mice were allocated into six groups: oral iCo-010 twice daily for 5 days in the dose of 20, 10, 5 and 2.5 mg/kg; vehicle control; and intravenous boluses of Fungizone® 2 mg/kg once daily for 5 days. The animals were sacrificed 12 h following the last administration and blood and tissues were collected.ResultsThe plasma concentrations of AmB were similar to previously reported after administration of iCo-009. Somewhat lower concentrations of AmB were detected in reticulo-endothelial system in the case of iCo-010 when compared with iCo-009. The concentration in kidney was higher with iCo-010 than with iCo-009. The creatinine levels in all oral treatment groups were in a normal range as in the case of iCo-009. Administration of Fungizone® resulted in elevated plasma creatinine levels. Histopathology analysis detected no GI, liver or kidney toxicity following multiple dose oral administration of iCo-010. Fungizone® treatment induced necrotic changes in hepatic and kidney tissues.ConclusionsGiven the tropical stability of iCo-010, near identical activity against visceral leishmaniasis and significant concentrations in target organs this formulation has a potential to become a treatment of choice in tropical developing countries.

Inhibition of intestinal absorption of cholesterol by surface‐modified nanostructured aluminosilicate compounds

The aim of this work was to assess the ability of aqueous suspensions of surface-modified nanostructured aluminosilicate (NSAS) compounds to reduce the intestinal absorption of cholesterol in a rat model. The rats were divided into 10 treatment groups which included several NSAS compounds at various doses, ezetimibe at 10 mg/kg, stigmastanol at 50 mg/kg, and normal saline. All compounds and controls were independently administered by oral gavage and then a mixture of [(3)H]cholesterol and cold cholesterol in 10% Intralipid(R) was immediately administered orally to the animals. Systemic blood was sampled and the concentration of cholesterol in plasma was determined by means of radioactivity. Protonation of NSAS using an ion-exchange column resulted in significant inhibition of cholesterol absorption relative to the control group (31.5% and 38.6% reduction in absorption of cholesterol for 50 and 100 mg/kg doses, respectively). Other surface-ion modifications of NSAS compounds did not show significant effect on intestinal cholesterol absorption. The inhibition of cholesterol absorption by ezetimibe was superior and by stigmastanol was equal to the effect of protonated NSAS in the doses investigated in this study. In conclusion, protonated NSAS material seems to inhibit significantly the intestinal absorption of dietary cholesterol in a rat model.

Assessment of novel oral lipid-based formulations of amphotericin B using an in vitro lipolysis model

The purpose of this study was to investigate the intraluminal processing of novel oral lipid-based formulations of amphotericin B using an in vitro lipolysis model. Amphotericin B (AmB) was formulated in three lipid-based formulations consisting of different lipid components: iCo-009, iCo-010 and iCo-011. Various lipid loads (0.25, 0.5, 1 and 2 g) were digested using the lipolysis model to assess AmB distribution among the lipolysis phases. The duration of lipolysis was comparable among the three formulations except for 2 g load of iCo-009 which had a significantly longer lipolysis than iCo-010 and iCo-011. The lipid components of iCo-009 experienced lower extent of lipolysis as compared to other formulations. Amphotericin B concentration in the aqueous phases was the highest with iCo-010 which also had the lowest sediment recovery. Amphotericin B levels in the undigested lipid layers were comparable between iCo-009 and iCo-010 and were higher than with iCo-011. Given the observation that iCo-010 had the highest aqueous micellar solubilization and the lowest sediment recovery of AmB among the tested formulations, these results could potentially be used to interpret and predict the in vivo performance of AmB- SEDDS formulations in future studies.

Biodistribution and tissue toxicity of amphotericin B in mice following multiple dose administration of a novel oral lipid-based formulation (iCo-009)

OBJECTIVES The purpose of this study was to assess the biodistribution and toxicity of amphotericin B (AMB) following multiple dose administration of an oral lipid-based formulation (iCo-009). METHODS BALB/c female mice were used. ICo-009 was administered twice daily for 5 days at doses of 2.5-20 mg/kg. Untreated animals, oral vehicle or intravenous Fungizone® (1 or 2 mg/kg) served as control groups. The animals were sacrificed 12 h following the last administration of AMB, and blood and multiple tissues were harvested for drug analysis and histopathological evaluation. Plasma or tissue samples were analysed for concentrations of AMB or creatinine by means of HPLC-UV. RESULTS A dose-dependent accumulation of AMB in liver, spleen, kidney and lung tissues was found. The concentration of the drug in all these organs exceeded the corresponding concentrations in plasma at the same dose. The concentrations of AMB in heart and brain were similar to the corresponding concentrations in plasma. Creatinine concentrations were elevated above normal concentrations in the 2 mg/kg Fungizone® group only. Histopathological analysis of kidney and liver tissues revealed a normal pattern in all treated groups, except the 2 mg/kg Fungizone® group. No gastrointestinal toxicity was found in this study. CONCLUSIONS A multiple dose treatment regimen with iCo-009 in mice results in a gradual accumulation of AMB in tissues. Despite significant concentrations of AMB, no kidney or liver toxicity of orally administered AMB was detected in this study. Furthermore, multiple oral administration of iCo-009 or of vehicle control did not induce gastrointestinal toxicity.

Association of the Endotoxin Antagonist E5564 with High-Density Lipoproteins In Vitro: Dependence on Low-Density and Triglyceride-Rich Lipoprotein Concentrations

ABSTRACT The objective of this study was to determine the distribution profile of the novel endotoxin antagonist E5564 in plasma obtained from fasted human subjects with various lipid concentrations. Radiolabeled E5564 at 1 μM was incubated in fasted plasma from seven human subjects with various total cholesterol (TC) and triglyceride (TG) concentrations for 0.5 to 6 h at 37°C. Following these incubations, plasma samples were separated into their lipoprotein and lipoprotein-deficient fractions by ultracentrifugation and were assayed for E5564 radioactivity. TC, TG, and protein concentrations in each fraction were determined by enzymatic assays. Lipoprotein surface charge within control and phosphatidylinositol-treated plasma and E5564’s influence on cholesteryl ester transfer protein (CETP) transfer activity were also determined. We observed that the majority of E5564 was recovered in the high-density lipoprotein (HDL) fraction. We further observed that incubation in plasma with increased levels of TG-rich lipoprotein (TRL) lipid (TC and TG) concentrations resulted in a significant increase in the percentage of E5564 recovered in the TRL fraction. In further experiments, E5564 was preincubated in human TRL. Then, these mixtures were incubated in hypolipidemic human plasma for 0.5 and 6 h at 37°C. Preincubation of E5564 in purified TRL prior to incubation in human plasma resulted in a significant decrease in the percentage of drug recovered in the HDL fraction and an increase in the percentage of drug recovered in the TRL and low-density lipoprotein fractions. These findings suggest that the majority of the drug binds to HDLs. Preincubation of E5564 in TRL prior to incubation in normolipidemic plasma significantly decreased the percentage of drug recovered in the HDL fraction. Modifications to the lipoprotein negative charge did not alter the E5564 concentration in the HDL fraction. In addition, E5564 does not influence CETP-mediated transfer activity. Information from these studies could be used to help identify the possible components of lipoproteins which influence the interaction of E5564 with specific lipoprotein particles.

Assessing the Antifungal Activity of a New Oral Lipid-Based Amphotericin B Formulation Following Administration to Rats Infected with Aspergillus Fumigatus

ABSTRACT The purpose of this study was to assess the antifungal activity of a new oral amphotericin B (AmpB) lipid-based formulation following administration to rats infected with Aspergillus fumigatus. Aspergillus fumigatus inoculum (2.1–2.5 × 107 colony forming units [CFU]) were injected via the jugular vein; 48h later male albino Sprague-Dawley rats (350–400 g) were administered either a single oral dose of AmpB incorporated into Peceol (50 mg AmpB/kg), physiologic saline (nontreated controls) or Peceol alone (vehicle control) once daily for 4 days. To assess antifungal activity Brain, Lung, Heart, Liver, Spleen and Kidney sections were homogenized with normal saline (1 mL/g of tissue) and a 0.1-mL aliquot was spread plated onto a Sabourand dextrose agar plate. The plates were incubated for 48 hr at 37°C, at which time the number of fungal CFU were determined and corrected for tissue weight. In addition, plasma galactomannan antigen concentrations were determined. Data was reported as mean ± standard error of the mean. The AmpB-Peceol oral formulation significantly decreased total fungal CFU concentrations recovered in all the organs added together, brain CFU concentrations, spleen CFU concentrations and plasma galactomannan antigen concentrations compared to baseline. No significant differences in lung, heart, liver and kidney CFU concentrations between treatment and control groups were observed. Peceol vehicle control did not exhibit any antifungal activity. These findings suggest that a new oral lipid-based formulation of AmpB incorporated into Peceol can significantly decrease brain and spleen CFU concentrations and plasma galactomannan antigen concentrations compared to non-treated controls.