The invention relates to monosaccharide derivatives and disaccharide derivatives and to methods for the preparation thereof. The invention further relates to the use of said derivatives in, inter alia, medical, pharmaceutical, cosmetic and food applications.
Sugar fatty acid esters are well-known for their emulsifying capacity. They can emulsify a large dispersing phase with a small continuous phase in either the oil-in-water and water-in-oil type. In addition, sugar fatty acid esters are well known for their wide range of HLB value (Hydrophylic-Lipophilic Balance, HLB values of sucrose esters may vary from <1 to 16). The HLB value of sugar fatty acid esters depend on the number of fatty esters per sugar molecule and the length of the carbon chain of the fatty acid ester.
Sugar fatty acid esters are further known for several other applications, such as for their ability to enhance or inhibit the crystallization of fats and oils, their anti-bacterial effects, their wetting and dispersing effects, their possible use in the inhibition of thermal and freezing denaturation of proteins, and for their enhancing effect of non-specific host defense.
Nigam et al. (Br. J. Cancer, 46, pp. 782-793, 1982) disclose the in vitro and in vivo immunostimulatory effects of various fatty acid esters of arabinose, galactose, glucose, mannose, cellobiose, lactose, maltose, and sucrose. Factors of increase in antibody responses varied from 1 to <10.
Nigam et al. (Cancer Res. 38, pp. 3315-3312, 1978) disclose immunopotentiating activity of disaccharide fatty acid esters, especially maltose tetrapalmitate.
Nishikawa et al. (Chem. Pharm. Bull. 29, pp. 505-513, 1981) disclose anti-tumor activity of sucrose fatty acid esters.
Azuma (EP 1,572,368) disclose enhancing effects of sugar fatty acid esters on vaccine efficacy, which is designated herein as ‘adjuvant activity’ or ‘adjuvanticity’.
Disaccharide fatty acid esters combined with a oil-in-water emulsion are well-known for their stimulatory effects on vaccine efficacy.
Nigam et al. (Br. J. Cancer, 46, pp. 782-793, 1982) also disclose a combination of sucrose fatty acid esters and oil-in-water emulsions of squalene and their use as adjuvant. However, of sucrose octaoleate esters it has been demonstrated that they show only weak, if any, stimulating effects on vaccine efficacy (see also Examples hereinbelow). Even combinations of sucrose octaoleate esters and an oil-in-water emulsion of squalane, demonstrated weak enhancing effects on vaccine efficacy which makes them inappropriate for the use(s) as vaccine adjuvant (see also Examples herein below).
Sucrose sulfate esters are also well-known. U.S. Pat. No. 3,432,489 discloses a method for the synthesis of various disaccharide polysulfates and of aluminum complexes therefrom, together with their relative therapeutic utilities. This patent, more specifically, describes the reaction of sucrose with many sulfating agents including chlorosulphonic acid or SO3-pyridine in various solvents including pyridine. In addition, U.S. Pat. No. 3,432,489 discloses the pharmaceutical and medical use(s) of sucrose sulfate esters, especially complexes of sucrose octasulfate ester with aluminum salts also known as sucralfate. The application of sucralfate in the treatment of gastro-intestinal disorders is well-known.
WO 90/02133 discloses a method for the preparation of sucrose sulfate esters and aluminum complexes thereof and formulations thereof for medical use(s).
Bazin et al. (Carbohydrate Res. 309, pp. 189-205, 1998) disclose the regioselective synthesis of sucrose-based surfactants through sulphonation of acylsucrose. The disclosed derivatives contain one acyl-group per sucrose molecule and one sulfate group per sucrose molecule. The disclosed method is a regioselective method for derivatization of certain hydroxyl groups of the sucrose molecule. The method uses dibutylstannylene complexes for the blocking of certain hydroxyl groups. A drawback of this method of preparation is its complexity.
Hilgers et al. (Immunology 60, pp. 141-146, 1986) disclose polysaccharides containing both fatty acid esters and sulfate esters, also known as sulpholipo-polysaccharides, and their use as adjuvants in vaccines. In addition, Hilgers et al. (Immunology 60, pp. 141-146, 1986; WO 96/20222) disclose a method of preparation of sulpholipo-polysaccharides by contacting the polysaccharide with an acoylchloride and then with a sulphonating agent.
Mashihi and Hilgers (EP-A-0-295,749) disclose a combination of sulpholipo-polysaccharides and oil-in-water emulsions, especially hydrophilic sulpholipo-polysaccharides with squalane-in-water emulsions. Mashihi and Hilgers (EP-A-0-295,749) further disclose enhancing effects of combinations of sulpholipo-polysaccharides, especially hydrophilic sulpholipo-polysaccharides and oil-in-water emulsions, especially squalane-in-water emulsion, on non-specific host defense mechanisms.
Hilgers et al. (Vaccine 12, pp. 653-660, 1994; Vaccine 12, pp. 661-665, 1994; WO 96/20008; Vaccine 17, pp. 219-228, 1999) disclose combinations of sulpholipo-polysaccharides, especially hydrophobic sulpholipo-polysaccharides and oil-in-water emulsions, especially squalane-in-water emulsions, mineral oil-in-water emulsions, soya oil-in-water emulsions and hexadecane-in-water. A method for the preparation of stable formulations of combinations of sulpholipo-polysaccharides, especially hydrophobic sulpholipo-polysaccharides and oil-in-water emulsions, especially squalane-in-water emulsions, mineral oil-in-water emulsions, soya oil-in-water emulsions and hexadecane-in-water is also disclosed.
The method for the preparation of sulpholipo-polysaccharides as disclosed in WO 96/20008 includes two steps; (1) first, the polysaccharide is contacted with an acoychloride and then (2) the lipidic polysaccharide derivative is contacted with a sulphonating agent. Both steps are considered to be ad random chemical addition reactions, meaning that the probability of each hydroxyl on the polysaccharide molecule being esterified, is equal and does not change during the process. This method of preparation of sulpholipo-polysaccharides results in the formation of different sulpholipo-polysaccharides derivatives varying in the number of fatty acid esters present per polysaccharide molecule, the number of sulfate esters present per polysaccharide molecule, the number of hydroxyl groups per polysaccharide molecule and the distribution of the fatty acid esters, the sulfate esters and the hydroxyl groups over the polysaccharide molecule. The number of chemically distinct sulpholipo-polysaccharides derivatives in a preparation obtained is determined by the number of distinct polysaccharide molecules in the starting material and by the number of hydroxyl groups per polysaccharide molecule.
To illustrate this point of the many, chemically distinct, sulpholipo-polysaccharide derivatives present in a preparation of sulpholipo-polysaccharide, the following example is included as disclosed by Hilgers et al. (WO 96/20008).
The best chemically-defined sulpholipo-polysaccharide derivative preparation known in the art, is the sulpholipo-polysaccharide preparation obtained from beta-cyclodextrin (also known as sulpholipo-cyclodextrin). This sulpholipo-cyclodextrin preparation is obtained from a polysaccharide with 7 glucose molecules per polysaccharide molecule. This sulpholipo-cyclodextrin preparation is derived from the lowest molecular weight polysaccharide and with the least number of hydroxyl groups disclosed. Beta-cyclodextrin has a molecular weight of 1153 Da and has 21 hydroxyl groups per molecule. These hydroxyl groups may be added chemically by a fatty acid ester or a sulfate ester or may remain unchanged. The derivatives present in a sulpholipo-cyclodextrin preparation vary in the number of fatty acid esters per beta-cyclodextrin molecule, the number of sulfate esters per beta-cyclodextrin molecule, the number of hydroxyl groups per beta-cyclodextrin molecule and the distribution of these fatty acid esters, sulfate esters and hydroxyl groups over the beta-cyclodextrin molecule. The number of chemically distinct derivatives in a sulpholipo-cyclodextrin preparation prepared according to the method known in the art (Vaccine 17, pp. 219-228, 1999; WO 96/20222) is extremely high. When the distribution of the fatty acid esters, the sulfate esters and the hydroxyl groups over the beta-cyclodextrine molecule is not taking into account, the number of chemically distinct derivatives in a sulpholipo-cyclodextrin preparation can be several hundreds (e.g. 210). In addition, when the distribution of the fatty acid esters, the sulfate esters and the hydroxyl groups over the beta-cyclodextrine molecule is taken into account, the number of chemically distinct derivatives in a sulpholipo-cyclodextrin preparation is33+{(33)7−33}/7=1,494,336,195.
The concentration of the chemically distinct derivatives present in a sulpholipo-cyclodextrin preparation can be modulated by varying the molar ratios or the weight ratios of the starting materials, i.e. beta-cyclodextrin, acoylchloride and sulphonating agent, as disclosed by Hilgers et al. (WO 96/20222). The concentration of the chemically distinct derivatives present in a sulpholipo-cyclodextrin preparation can be estimated mathematically. Provided that both chemical reactions involved in the preparation of the sulphoplipo-polysaccharide derivatives are fully ad random, the maximal concentration of a certain derivative present in a sulpholipo-cyclodextrin preparation is most often less than 5%. A preparation of sulpholipo-polysaccharide obtained from a polysaccharide with even larger numbers of hydroxyl groups per molecule than beta-cyclodextrin, will contain an even higher number of chemically distinct derivatives and contains accordingly lower concentrations of each derivative.
Thus it can be concluded that a sulpholipo-polysaccharide preparation obtained as disclosed by Hilgers et al. (WO 96/20222; WO 96/20008) contains many chemically distinct derivatives, which may be disadvantageous under certain circumstances. Also, the fact that a specific derivative is present only in very small amounts could be disadvantageous.
A drawback of the sulpholipo-polysaccharides is that they have various physical, chemical and physicochemical properties (such as solubility, tensio-activity) which while being appropriate for their intended use (e.g. as detergent or emulsifier), are not appropriate for use with other molecules and/or other uses. For this reason, it is desired to separate the ‘inappropriate’ sulpholipo-polysaccharide derivatives from ‘appropriate’ sulpholipo-polysaccharide derivatives. Such separation might be carried out by classical separation techniques well-known in the art. However, as has been mentioned, the concentration of the ‘appropriate’ derivative(s) in a sulpholipo-polysaccharide preparation are relatively low. Also, the chemical and physical properties of the ‘inappropriate’ sulpholipo-polysaccharide derivatives and of the ‘appropriate’ sulpholipo-polysaccharide derivatives may be quite similar. Therefore, the separation procedure may be complicated, costly and time-consuming.
A further drawback of the preparation of sulpholipo-polysaccharides as disclosed by Hilgers et al. (WO 96/20222; WO 96/20008) includes the fact that relatively large quantities of organic solvents are used which need to be removed from the final sulpholipo-polysaccharide preparation. This can often prove difficult and/or involve the use of procedures which are difficult, costly, and even dangerous, especially on an industrial scale.
Accordingly, there remains a clear need for sugar derivatives which possess physicochemical and/or biological and/or biopharmaceutical properties that permit a wide use for various purposes. There further remains a need for an easy, safe and inexpensive method for the preparation of such sugar derivatives on an industrial scale.
It is an object of the present invention to provide sugar derivatives which are capable of forming stable formulations with a wide variety of water-immiscible molecules. The objective sugar derivatives should possess highly advantageous physical and/or physicochemical and/or biological and/or pharmaceutical properties, making them suitable for use in a variety of applications, such as medical applications, for instance in the preparation of vaccines and/or adjuvants for vaccines. It is further an object of the invention to provide a simple, easy, and inexpensive method for the preparation of such sugar derivatives.