William J. Christ

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

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. As measured by release by tumour necrosis factor‐α, 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. 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‐α was inhibited by more than 98%. The addition of E5531 1 h after lipopolysaccharide reduced the efficacy of E5531 by 47%. Antagonistic activity of E5531 was specific for lipopolysaccharide as it was ineffective at inhibiting interferon‐γ 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‐α induced E‐selectin expression in human umbilical vein endothelial cells. E5531 as well as MY4, an anti‐CD14 antibody, inhibited radiolabelled lipopolysaccharide binding in human monocytes. These results support our contention that E5531 is a potent antagonist of lipopolysaccharide‐induced release of tumour necrosis factor‐α and other cellular mediators and may be an effective therapeutic agent for human septic shock due to Gram‐negative bacteria.

Structure–activity relationships of Halichondrin B analogues: modifications at C.30–C.38

Structurally simplified analogues of halichondrin B were prepared by total synthesis and found to retain potent cell growth inhibitory activity in vitro.

Evaluation of a Group A Streptococcus synthetic oligosaccharide as vaccine candidate

Bacterial infections caused by Group A Streptococcus (GAS) are a serious health care concern that currently cannot be prevented by vaccination. The GAS cell-wall polysaccharide (GAS-PS) is an attractive vaccine candidate due to its constant expression pattern on different bacterial strains and protective properties of anti-GAS-PS antibodies. Here we report for the first time the immunoprotective efficacy of glycoconjugates with synthetic GAS oligosaccharides as compared to those containing the native GAS-PS. A series of hexa- and dodecasaccharides based on the GAS-PS structure were prepared by chemical synthesis and conjugated to CRM(197). When tested in mice, the conjugates containing the synthetic oligosaccharides conferred levels of immunoprotection comparable to those elicited by the native conjugate. Antisera from immunized rabbits promoted phagocytosis of encapsulated GAS strains. Furthermore we discuss variables that might correlate with glycoconjugate immunogenicity and demonstrate the potential of the synthetic approach that benefits from increased antigen purity and facilitated manufacturing.

Selective formation of C-2 azidodeoxy-d-glucose derivatives from d-glucal precursors using the azidonitration reaction

A series of glucals, protected by cyclic acetal protecting groups to conformationally constrain the C-4 and C-6 hydroxyl groups, were subjected to the azidonitration reaction to furnish the corresponding C-2 azidodeoxy-D-glucoses. 4,6-O-Isopropylidene-3-O-triisopropylsilyl-D-arabino-hex-1-enit ol afforded 2-azido-2-deoxy-4,6-O-isopropylidene-3-O-triisopropylsilyl-D-gluco pyranosyl nitrate and its D-manno isomer in a 20:1 ratio. These findings allow the azidonitration reaction to be now used for the preparation of a variety of glucosamine building blocks from differentially protected glucal precursors.