Synthesis of 2-deoxy-4-O-phosphono-3-O-tetradecanoyl-2-[(3R)- and (3S)-3-tetradecanoyloxytetradecanamido]-D-glucose: a diastereoisomeric pair of 4-O-phosphono-D-glucosamine derivatives (GLA-27) related to bacterial lipid A

X-ray diffraction and high-resolution NMR spectroscopic analysis of 2,4,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosono-1,5-lactone

The X-ray diffraction and high-resolution 1H and 13C NMR spectral data are reported for 2,4,7,8-tetra-O-acetyl-3-deoxy-alpha-D-manno-2-octulopyranosono-1,5-lactone.

3-O-Desacyl monophosphoryl lipid A derivatives: synthesis and immunostimulant activities

The synthesis of a series of novel analogues of lipid A, the active principle of lipopolysaccharide, is reported. In these compounds, the 1-O-phosphono and (R)-3-hydroxytetradecanoyl moieties of native Salmonella minnesota R595 lipid A have been replaced with hydrogen and the length of the normal fatty acyl residues has been systematically varied. Normal fatty acid chain length in the 3-O-desacyl monophosphoryl lipid A (MLA) series is shown to be a critical determinant of iNOS gene expression in activated mouse macrophages and the induction of proinflammatory cytokines in human peripheral monocytes. Examination of pyrogenicity in rabbits and lethal toxicity in D-galactosamine-treated mice shows that toxic effects in the MLA series can be ameliorated by modifying fatty acid chain length. When used as an adjuvant for tetanus toxoid vaccines, certain MLA derivatives enhance the production of tetanus toxoid-specific antibodies in mice.

DT-5461, a new synthetic lipid A analogue, inhibits lung and liver metastasis of tumor in mice

We have investigated the antimetastatic effect of a new synthetic lipid A analogue, of low endotoxicity, DT-5461, against two highly metastatic tumor cell lines, L5178Y-ML25 T-lymphoma and B16-BL6 melanoma cells in mice. Four intermittent i.v. administrations of DT-5461 at intervals of 4 days resulted in a significant inhibition of liver metastasis caused by i.v. injection of L5178Y-ML25 cells and lung metastasis of B16-BL6 cells in the experimental metastasis models. Intraperitoneal and intranasal administrations as well as i.v. administration of DT-5461 were also effective in preventing lung metastasis of the melanoma cells. Multiple administrations of DT-5461 before the surgical excision of primary tumors significantly reduced the number of lung colonies of melanoma cells and primary tumor size. Similarly, this treatment modality after the surgical excision of primary tumors showed a greater reduction of lung tumor colonies as compared with lipopolysaccharide, a synthetic lipid A (No. 506) and its analogue as well as untreated control in the spontaneous lung metastasis model. Furthermore, the group that received DT-5461 after the inoculation of lymphoma or melanoma cells showed significantly enhanced survival rate compared with the untreated control. These results suggested that DT-5461 may be therapeutically useful for the inhibition of tumor metastasis.

SDZ MRL 953, a novel immunostimulatory monosaccharidic lipid A analog with an improved therapeutic window in experimental sepsis

SDZ MRL 953, a new synthetic monosaccharidic lipid A, was investigated in vitro and in vivo for immunopharmacological activities. In experimental models of microbial infections, the compound was highly protective when it was administered prophylactically either once or three times to myelosuppressed or immunocompetent mice. The 50% effective doses of SDZ MRL 953 varied with the infectious agents and the route of its administration. In all cases, the 50% effective doses were about 10(3) times higher than those obtained with endotoxin from Salmonella abortus equi. SDZ MRL 953 was, however, less toxic than lipopolysaccharide by a factor of 10(4) to greater than 7 x 10(5) times in galactosamine-sensitized mice. The compound was also an effective inducer of tolerance to endotoxin. Hence, repeated dosing with the compound induced a transient resistance (greater than or equal to 1 week) to lethal challenges with endotoxin. In vitro, the compound was devoid of intrinsic antimicrobial activity, but it moderately induced the release of cytokines from monocytes and primed human neutrophils for the enhanced production of reactive oxygen metabolites in response to a soluble stimulus. The results presented here suggest that SDZ MRL 953 may be useful in a clinical setting for enhancing resistance to infections, particularly in patients undergoing myelosuppressive chemotherapy or irradiation, and for the prophylaxis of endotoxin shock.

Activation by synthetic lipid A subunit analogues (GLA compounds) of tumoricidal properties in human blood monocytes

The authors have determined that synthetic lipid A subunit analogues (GLA compounds), as well as E. coli type lipopolysaccharide (LPS) and synthetic lipid A (compound 506), are able to stimulate human monocytes to become cytotoxic against tumour target cells in vitro. GLA-60, a synthetic lipid A subunit analogue of low toxicity, was found to be more active for the induction of tumoricidal monocytes than GLA-59, and similar to that of LPS. GLA-60 could induce not only the secretion of cytotoxic factor into the culture supernatant but also expression of the membrane-associated form of cytotoxic factor in human monocytes. Supernatant-mediated cytotoxicity was completely inhibited by the addition of monoclonal anti-human TNF antibody. These results indicate that a synthetic lipid A subunit analogue, GLA-60, would be a useful activator of tumoricidal monocytes in spite of its low toxicity.

Production of interleukin 1 from human monocytes stimulated by synthetic lipid A subunit analogues

We have investigated that synthetic lipid A subunit analogues (GLA compounds) as well as E. coli type lipopolysaccharide (LPS) and synthetic lipid A (compound 506) are able to stimulate human monocytes to release IL-1 in vitro. Of monosaccharide-type GLA compounds, GLA-60 was found to be more active for the induction of IL-1 production than GLA-59 and GLA-27, and similar to that of LPS or compound 506. GLA-60 could induce not only the secretion of IL-1 into culture supernatant but also the expression of membrane-associated form of IL-1 in human monocytes. Furthermore, no detectable IL-2 activity was observed in the culture supernatant. These results show that synthetic lipid A analogues of low toxicity, in particular GLA-60, are active in inducing IL-1 production in human monocytes.

Adjuvant activities of synthetic lipid A subunit analogues and its conjugates with muramyl dipeptide derivatives

We investigated the effects of the active principle of lipopolysaccharide (LPS), synthetic lipid A (compound 506), and of its related compounds GLA-60, -59 and -27, on murine macrophage activation and cytokine induction. GLA-60, which is devoid of endotoxic activity, showed interleukin-1 (IL-1)-inducing activity and activation of murine macrophages comparable to those of LPS or compound 506. The biological activities of six conjugates of GLA-60 with MDP derivatives GMD-323 to -328 were investigated in this study. All the GMD compounds except GMD-323 showed potent inducing activities for IL-1 and tumoricidal macrophages, especially GMD-324 and -326, which exhibited much higher activity than GLA-60. However, TNF- and CSF-inducing activities of these conjugates were lower than those of GLA-60. IL-1-inducing activity of the mixture of MDP derivative (GMD-267) and GLA-60 was higher than that of the conjugates (GMD-324) or that of GLA-60 and GMD-267 alone.

Structural requirements of lipid A for endotoxicity and other biological activities

For the past ten years, several groups were engaged in synthetic studies of lipid A, namely the lipid portion of bacterial lipopolysaccharides (LPS) that has been assumed to be the bioactive center of LPS, but has not been unanimously approved. Among them, Shiba, Kusumoto, and colleagues, Osaka, Japan have synthesized most energetically and successfully a variety of counterparts of lipid As, biosynthetic lipid A precursors, and their analogs. The endotoxic and related bioactivities of these synthetic compounds were studied by Japanese and German groups, including ours. In 1985, one of the compounds, having an acylation and phosphorylation pattern in beta(1-6)-D-glucosamine disaccharide which was proposed for Escherichia coli F515 lipid A was found to be exhibit full endotoxic and related bioactivities identical to those of the bacterial product. The study was extended by synthesis and examination of bioactivities of variously acylated D-glucosamine di- and monosaccharide phosphates, which correspond to structural components of lipid As, and their analogs or derivatives. Thus, structural requirements have been fairly well elucidated. In this article, first we will review the progress of synthetic and biological studies, with particular emphasis on chemical structure--bioactivities relationships of lipid As, and then we will discuss possible usefulness of some less or nontoxic lipid A-related synthetic compounds in clinical and preventive medicine.

Effect of stereospecificity of chemically synthesized lipid A-subunit analogues GLA-27 and GLA-40 on the expression of immunopharmacological activities

Tumor necrosis factor (TNF)-inducing, mitogenic, polyclonal B cell activation (PBA), macrophage activation and antiviral activities of chemically synthesized lipid A-subunit analogues, GLA-27 and GLA-40, were investigated. The structure of GLA-27 comprises 4-O-phosphono-D-glucosamine carrying tetradecanoyl and 3-tetradecanoyloxytetradecanoyl [C14-O-(C14)] groups as the 3-O- and 2-N-acyl substituents, respectively. GLA-40 is a 1-deoxy compound of GLA-27. The activities of stereoisomers, (R) and (S) forms at the C3 position of the C14-O-(C14) group, of both compounds were also investigated. TNF-inducing activity of the (S) isomers of GLA-27 and GLA-40 was stronger than that of the (R) isomers while the (R) isomers exhibited stronger mitogenic and PBA activities than the (S) isomers. With respect to macrophage activation such as phagocytosis, acid phosphatase and N-acetyl-beta-D-glucosaminidase activity as cellular lysosomal enzymes and cytostasis, peritoneal macrophages obtained from mice administered i.p. with test samples showed significant activities. Among stereoisomers of GLA-27, the (R) isomer exhibited somewhat stronger phagocytic and lysosomal enzyme activities than those of the (S) isomer while there was no appreciable difference in the activities between the isomers of GLA-40. Significant cytostasis-inducing activity was observed in stereoisomers tested. All of the isomers showed remarkable antiviral activity against vaccinia virus.

Synthesis of the optically active 4-O-phosphono-D-glucosamine derivatives related to the nonreducing-sugar subunit of bacterial lipid A

The optically active lipid A-subunit homologs named GLA-46, GLA-47, GLA-59, and GLA-60 have been synthesized stepwise by successive acylation at N-2 and O-3 of benzyl 2-amino-2-deoxy-4,6-O-isopropylidene-beta-D-glucopyranoside with the 3-9O-(benzyloxy)methyl or 39O-tetradecanoyl derivative of optically active 3-hydroxytetradecanoic acid, and phosphorylation at O-4 of the D-glucosamine residue.

Structural requirements for inducing in vitro B lymphocyte activation by chemically synthesized derivatives related to the nonreducing D-glucosamine subunit of lipid A

Mitogenic and polyclonal B cell activation (PBA) activities of 16 synthetic compounds related to the nonreducing D-glucosamine (GlcN-II) subunit of lipid A were investigated. Among compounds possessing the GlcN backbone, a 4-O-phosphorylated GlcN derivative carrying N-linked 3-tetradecanoyloxytetradecanoyl [C14-O-(C14)] and 3-O-linked tetradecanoyl (C14) groups, GLA-27, expressed the highest degree of both activities. Omission of the 3-O-linked C14 group from GLA-27 and transfer of the C14 group to the C-6 position induced critical changes in expression of activities. Both 4-O-phosphorylated compounds carrying an N-linked C14 or 3-hydroxytetradecanoyl (C14OH) group instead of the C14-O-(C14) group in GLA-27 showed no detectable activity. Substituting a 3-O-linked C14 group in GLA-27 for the C14-O-(C14) group also markedly decreased mitogenic and PBA activities. Change of phosphorylation site from the C-4 to the C-6 position and bisphosphorylation at the C-4 and C-6 positions induced somewhat weak depression. Much weaker activities were observed in a compound carrying N-linked 3-dodecanoyloxydodecanoyl [C12-O-(C12)] and 3-O-dodecanoyl (C12) as fatty acid substituents. No detectable activity was seen in a compound carrying N-linked 3-hexadecanoyloxyhexadecanoyl [C16-O-(C16)] and 3-O-hexadecanoyl (C16), indicating that the most suitable carbon chain length for expressing the activities is C14. Regarding structural change of the GlcN backbone, a 1-deoxy derivative of GLA-27 exhibited stronger activity than did GLA-27 itself. Mitogenic and PBA activity of GLA-27 were stronger than those of lipid X, which corresponds to the reducing D-GlcN (GlcN-I) subunit of Escherichia coli lipid A and is a 1-O-phosphorylated GlcN derivative carrying N- and 3-O-linked C14OH groups. These results indicate that N-linked acyloxyacyl and 3-O-linked acyl groups and phosphorylation are critical for expressing both mitogenic and PBA activities.