E5531, a synthetic non‐toxic lipid A derivative blocks the immunobiological activities of lipopolysaccharide

Abstract

1 The major pathological responses to Gram-negative bacterial sepsis are triggered by endotoxin or lipopolysaccharide. As endotoxin is shed from the bacterial outer membrane, it induces immunological responses that lead to release of a variety of cytokines and other cellular mediators. As part of a program aimed at developing a therapeutic agent for septic shock, we have developed E5531, a novel synthetic lipopolysaccharide antagonist. 2 As measured by release by tumour necrosis factor-a, human monocytes or whole blood can be activated by lipopolysaccharide, lipid A, and lipoteichoic acid (from Gram-positive bacteria). E5531 potently antagonizes activation by all these agents while itself being devoid of agonistic activity. 3 The inhibitory activity of E5531 was dependent on time of addition. When 10 nM E5531 was added simultaneously with lipopolysaccharide or 1 ± 3 h before addition of lipopolysaccharide, production of tumour necrosis factor-a was inhibited by more than 98%. The addition of E5531 1 h after lipopolysaccharide reduced the ecacy of E5531 by 47%. 4 Antagonistic activity of E5531 was speci®c for lipopolysaccharide as it was ineective at inhibiting interferon-g mediated NO release of RAW 264.7 cells, phorbor 12-myristate 13-acetate stimulated superoxide anion production in human neutrophils, concanavalin A stimulated mitogenic activity in murine thymocytes and tumor necrosis factor-a induced E-selectin expression in human umbilical vein endothelial cells. 5 E5531 as well as MY4, an anti-CD14 antibody, inhibited radiolabelled lipopolysaccharide binding in human monocytes. 6 These results support our contention that E5531 is a potent antagonist of lipopolysaccharideinduced release of tumour necrosis factor-a and other cellular mediators and may be an eective therapeutic agent for human septic shock due to Gram-negative bacteria.

Consequences of Interaction of a Lipophilic Endotoxin Antagonist with Plasma Lipoproteins

“…As reported previously (15,25), the in vitro activity of E5531 decreased in the presence of high serum concentrations. An approximately 20-fold difference in potency is observed when E5531 was tested in in vitro assays with monocytes (1% serum; mean IC 50 , 0.11 nM) and whole-blood assays (80% serum; mean IC 50 , 2.3 nM).…”

A Synthetic TLR4 Antagonist Has Anti-Inflammatory Effects in Two Murine Models of Inflammatory Bowel Disease

“…They also tested a TLR4R complex antagonist, E5531, and showed it also bound directly to TLR4-MD-2. As E5531 has very similar LPS-antagonist activity compared with CRX-526 (32,33), it is possible that CRX-526 also binds directly to a TLR4-MD-2 complex.…”

MD-2 Mediates the Ability of Tetra-Acylated and Penta-Acylated Lipopolysaccharides to AntagonizeEscherichia coliLipopolysaccharide at the TLR4 Signaling Complex

“…Penta-acylated LPS isolated from Rhodobacter sphaeroides also exhibits the ability to antagonize E. coli LPS (17). In addition, synthetic penta-acylated lipid A-like compound, E5531, is an antagonist for LPS-dependent cell activation that has been considered as a potential therapeutic agent for bacterial-induced septic shock (19,20).…”