e-5531 and Endotoxemia

Therapy for Gram-negative sepsis remains unsatisfactory despite a concerted effort to develop new treatments for this common, life-threatening syndrome. Current research continues on several fronts to improve the treatment options available to clinicians in the management of these critically ill patients. Recently, a greater understanding of the complex molecular basis of endotoxin-mediated pathophysiological effects in humans has generated a number of novel therapeutic agents for sepsis. Several of these treatment strategies have already entered clinical trials and it is hoped that some of these therapies will become widely available in the near future. In this review, the current status of the most promising new antiendotoxin agents is summarised, and the major obstacles to the successful clinical development of these therapies are described. New antiendotoxin therapies include those which interrupt the synthesis of endotoxin, bind and neutralise its activity, prevent endotoxin interactions with host effector cells and interfere with endotoxin-mediated signal transduction pathways. Potential therapeutic strategies involving these agents consist of endotoxin analogues, antibodies, subunit vaccines, binding columns, recombinant human proteins and small molecule inhibitors of endotoxin synthesis and intracellular signalling. The pitfalls of previous antiendotoxin clinical investigations and the perils of future clinical trial designs are discussed in the context of unmet needs and realistic expectations for success. While considerable progress has been made, effective and new treatments for Gram-negative bacterial sepsis continues to elude us at the present time. This has been to the detriment of patients, investigators and pharmaceutical companies alike. It will require focused efforts by basic scientists, continued support by industry and enlightened study designs by clinical investigators to successfully develop antiendotoxin in therapies for use in septic patients in the future.

Topics: Anti-Bacterial Agents; Antibodies; Antigen-Antibody Complex; Antimicrobial Cationic Peptides; Bacterial Vaccines; Blood Proteins; Endotoxemia; Endotoxins; Gram-Negative Bacteria; Humans; Lipid A; Lipopolysaccharide Receptors; Lipopolysaccharides; Membrane Proteins; Recombinant Proteins; Shock, Septic

To evaluate the efficacy of a novel lipopolysaccharide (LPS) antagonist, E5531, in blocking LPS-induced cardiac responses including myocardial depression (as assessed by relatively load-independent echocardiographic indices of contractility) in a human model of experimental endotoxemia.. Randomized, prospective, placebo-controlled, double-blind trial.. ICU procedure room.. Thirty-two healthy, male volunteers.. Administration of LPS (4 ng/kg) and either a placebo or one of four sequential doses of E5531 (100 microg, 250 microg, 500 microg, or 1,000 microg) followed by volumetric echocardiography before and during 4-L saline solution infusion (3 L over 3 h, followed by 1 L over 2 h).. In addition to the generation of a hyperdynamic circulation throughout the study period, administration of LPS resulted in a biphasic contractility response. Ejection fraction (EF), rate-corrected mean velocity of circumferential fiber shortening (Vcfc), peak systolic BP (SBP)/end-systolic volume index (ESVI) ratio, and end-systolic pressure (Pes)/ESVI ratio increased at the 3-h post-LPS assessment, compared to a control group of subjects receiving only similar amounts of saline solution (minimum p < 0.001). End-systolic myocardial wall stress (sigmaes)/ESVI ratio, one of the most load independent of the contractility indices, was unchanged. At 5 h after endotoxin, EF, Vcfc, SBP/ESVI, Pes/ESVI, and sigmaes/ESVI were all decreased (minimum p < 0.01), indicating myocardial depression. When present, early (3 h after LPS), apparent enhancement of myocardial contractility and later (5 h after LPS) myocardial depression were substantially blunted by administration of E5531 (minimum p < 0.025), typically in a concentration-dependent manner.. Endotoxin generates significant myocardial depression when measured using highly load-independent indices of cardiac contractility. E5531 is a potent inhibitor of the early hyperdynamic cardiovascular and later myocardial depression response seen in experimental human endotoxemia.

Topics: Adolescent; Adult; Cardiac Output, Low; Dose-Response Relationship, Drug; Double-Blind Method; Endotoxemia; Escherichia coli; Hemodynamics; Humans; Intensive Care Units; Lipid A; Lipopolysaccharides; Male; Myocardial Contraction

Endotoxin (lipopolysaccharide [LPS]) has been associated with sepsis and the high mortality rate seen in septic shock. The administration of a small amount of LPS to healthy subjects produces a mild syndrome qualitatively similar to that seen in clinical sepsis. We used this model to test the efficacy of an endotoxin antagonist, E5531, in blocking this LPS-induced syndrome.. In a placebo-controlled, double-blind study, we randomly assigned 32 healthy volunteers to four sequential groups (100, 250, 500, or 1000 microg of E5531). Each group of eight subjects (six assigned to E5531, two assigned to placebo) received a 30-min intravenous infusion of study drug. LPS (4 ng/kg) was administered to all subjects as an intravenous bolus in the contralateral arm at the midpoint of the infusion. Symptoms, signs, laboratory values, and hemodynamics (by echocardiogram) were evaluated at prospectively defined times.. In subjects receiving placebo, LPS caused headache, nausea, chills, and myalgias. E5531 led to a dose-dependent decrease in these symptoms that was statistically significant (p < .05) except for myalgias. The signs of endotoxemia (fever, tachycardia, and hypotension) were consistently inhibited at the three higher doses (250, 500, and 1000 microg, p < .05). Tumor necrosis factor-alpha and interleukin-6 blood levels were both lower in those who received E5531 (p < .0001). The C-reactive protein level and white blood cell count response were decreased at all doses (p < .0001). The hyperdynamic cardiovascular state (high cardiac index and low systemic vascular resistance) associated with endotoxin challenge was significantly inhibited at the higher doses of E5531.. E5531 blocks the symptoms and signs and cytokine, white blood cell count, C-reactive protein, and cardiovascular response seen in experimental endotoxemia. This agent is a potent inhibitor of endotoxin challenge in humans and may be of benefit in the prevention or treatment of sepsis and septic shock.

Topics: Adolescent; Adult; Double-Blind Method; Endotoxemia; Humans; Lipid A; Lipopolysaccharides; Male

Sepsis and endotoxaemia are important causes of morbidity and mortality in humans. Research on sepsis focuses on rodent models most of which are poorly responsive to lipopolysaccharide (LPS), and thus do not mimic very well the high sensitivity of humans. Therefore, there is a need to develop more clinically relevant models. Horses suffer from a similar endotoxaemic syndrome to humans with high morbidity and mortality. LPS analogues that act as antagonists at Toll-like receptor 4 (TLR4) are being developed as novel treatments for endotoxaemia. Due to differences in recognition of ligands by TLR4 from different mammalian species, individual LPS molecules may act as agonists in some species and antagonists in others. The synthetic lipid A analogue E5531 is an antagonist at TLR4 in humans and mice, but its effects at TLR4 from other species are unknown. In the studies reported here, Escherichia coli LPS is a full agonist on equine bone marrow macrophage-like cells and its effects are antagonised by E5531. Similarly, E. coli LPS is an agonist and E5531 an antagonist on monocytes isolated from peripheral blood of healthy horses and human embryonic kidney (HEK) cells, transiently transfected to express horse TLR4 and its associated cell surface proteins MD2 and CD14. In contrast, both E. coli LPS and E5531 behave as agonists in horse whole blood by inducing production of equivalent amounts of the inflammatory mediator prostaglandin. This finding suggests that modification of E5531 may occur in whole blood, for example, deacylation, which alters its activity. This comparative study has revealed a novel pharmacological action of E5531 and emphasises the importance of extending studies of this nature beyond the normal rodent models.

Topics: Animals; Cell Line; Dinoprostone; Disease Models, Animal; Endotoxemia; Epoprostenol; Female; Humans; In Vitro Techniques; Interferon-gamma; Lipid A; Lipopolysaccharides; Male; Mice; Monocytes; Recombinant Proteins; Sepsis; Species Specificity; Toll-Like Receptor 4; Transfection