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Synthetic bile acid compositions and methods

Synthetic bile acid compositions and methods description/claims

This application claims the benefit under 35 U.S.C. 119(e) to provisional applications U.S. Ser. No. 60/945,035 filed on Jun. 19, 2007 and U.S. Ser. No. 60/956,875 filed on Aug. 20, 2007, each of which is incorporated herein by reference in its entirety.

The present invention relates broadly to bile acids and related compositions and methods. In one aspect, the present invention relates to deoxycholic acid and related compositions, useful intermediates, and methods for synthesis thereof. In another aspect, the present invention relates to use of the present compositions and methods as pharmaceutical compositions as well as methods for the manufacture thereof. Importantly, the bile acids of the present invention are not isolated from mammalian and microbial organisms naturally producing these acids and thus are free of any toxins and contaminants associated with such organisms.

Cholanology, the study of bile acids, and particularly bile acid chemistry has been of interest for the better part of a century. Although much is known, bile acid chemistry involves a wide variety of chemical entities, many with surprising properties. For a review, see, e.g., Mukhopadhyay, S. and U. Maitra., Current Science 87: 1666-1683 (2004) (“Chemistry and biology of bile acids”), incorporated herein by reference.

Bile acids are characterized by two connecting units, a rigid steroid nucleus and a short aliphatic side chain (see FIG. 1 of the present application). See, Hofmann, A. F., et al. For a proposed nomenclature for bile acids, see J. Lipid Res. 33:599-604 (1992). Both the nucleus and the side chain have a large number of possible steric arrangements. The nucleus can be altered by expansion or contraction of individual rings, and the side chain can be shortened or lengthened. In addition, both parts of the bile acid molecule have a large number of possible polar substituents. Ionizing groups may be present on the nucleus or the side chain. Finally, conjugating groups may be present on the nucleus (e.g., sulfate, glucuronate, phosphate) or on the side chain (glycine or taurine or other amino acids, or even sugars). The side chain structure determines the class of the compound (bile acids or bile salts).

Bile acids are amphiphiles, having both an amphiphilic and amphipathic “face”:

Hofman, A. F., News Physiol. Sci. 14: 24-29 (1999)(“Bile Acids: The good, the Bad, and the Ugly”, at 25, FIG. 1).

By convention, the hydrophobic surface is called the “β-face” and the hydrophilic surface is called the “α-face”. The β-face is lipid soluble and the α-face is relatively polar, in general. There are bile acids, such as those having polar groups (hydroxyl groups, in naturally occurring bile acids) on the hydrophobic face as well as on the hydrophilic face, e.g., ursodeoxycholic acid. The amphipathic nature of the molecule is responsible for its forming mixed micelles with amphipathic but water-insoluble lipids, such as phosphatidylcholine. Bile acids will not solubilize dietary lipids in the form of mixed micelles unless bile acids are above a critical concentration, termed the critical micellization concentration.

The bile acids found in greatest proportion in humans are chenodeoxycholic acid and deoxycholic acid. Deoxycholic acid is also known as deoxycholate, cholanoic acid, and 3α,12α-dihydroxy-5β-cholanate. In the human body deoxycholic acid is used in the emulsification of fats for the absorption in the intestine. In research, deoxycholic acid is used as a mild detergent for the isolation of membrane associated proteins. When substantially pure, deoxycholic acid is a white to off-white crystalline powder form. Deoxycholic acid is one of the four main acids produced by the liver. It is soluble in alcohol and acetic acid. The CAS number for deoxycholic acid is [83-44-3].

Rapid removal of body fat is an age-old ideal, and many substances have been claimed to accomplish such results, although few have shown results. “Mesotherapy”, or the use of injectables for the removal of fat, is not widely accepted among medical practitioners due to safety and efficacy concerns, although homeopathic and cosmetic claims have been made since the 1950's. Mesotherapy was originally conceived in Europe as a method of utilizing cutaneous injections containing a mixture of compounds for the treatment of local medical and cosmetic conditions. Although mesotherapy was traditionally employed for pain relief, its cosmetic applications, particularly fat and cellulite removal, have recently received attention in the United States. One such reported treatment for localized fat reduction, which was popularized in Brazil and uses injections of phosphatidylcholine, has been erroneously considered synonymous with mesotherapy. Despite its attraction as a purported “fat-dissolving” injection, the safety and efficacy of these cosmetic treatments remain ambiguous to most patients and physicians. See, Rotunda, A. M. and M. Kolodney, Dermatologic Surgery 32: 465-480 (2006) (“Mesotherapy and Phosphatidylcholine Injections: Historical Clarification and Review”).

WO 2006/133160 (incorporated herein by reference in its entirety including figures) describes methods for lipomodeling, e.g., reduction of a fat depot, by administering a neuropeptide Y receptor antagonist to the site of the fat depot. Kolonin M. G. et al., Nat. Med. June 10(6):625-32 (2004), describes fat selective pro-apoptotic peptides having potent fat cell killing effects. The described pro-apoptotic peptides require access to the vasculature to kill.

Recently published literature reports that deoxycholic acid has fat removing properties when injected into fatty deposits in vivo. See, WO 2005/117900 and WO 2005/112942, as well as US2005/0261258; US2005/0267080; US2006/127468; and US20060154906, all incorporated herein by reference in their entirety including figures). Deoxycholate injected into fat tissue has two effects: 1) it kills fat cells via a cytolytic mechanism; and 2) it causes skin tightening. Both of these effects are required to mediate the desired aesthetic corrections (i.e., body contouring). Because deoxycholate injected into fat is rapidly inactivated by exposure to protein and then rapidly returns to the intestinal contents, its effects are spatially contained. As a result of this attenuation effect that confers clinical safety, fat removal therapies typically require 4-6 sessions. This localized fat removal without the need for surgery is beneficial not only for therapeutic treatment relating to pathological localized fat deposits (e.g., dyslipidemias incident to medical intervention in the treatment of HIV), but also for cosmetic fat removal without the attendant risk inherent in surgery (e.g., liposuction). See, Rotunda et al., Dermatol. Surgery 30: 1001-1008 (2004) (“Detergent effects of sodium deoxycholate are a major feature of an injectable phosphatidylcholine formulation used for localized fat dissolution”) and Rotunda et al., J. Am. Acad. Dermatol. (2005: 973-978) (“Lipomas treated with subcutaneous deoxycholate injections”), both incorporated herein by reference.

Pharmaceutical grade bile acid preparations are commercially available at relatively low cost. This low cost is due to the fact that the bile acids are obtained from animal carcasses, particularly large animals such as cows and sheep. Importantly, as with all medicaments from animal sources, there is concern that the animal-derived bile acid products may contain animal pathogens and other harmful agents such as animal or microbial metabolites and toxins, including bacterial toxins such as pyrogens.

Such animal pathogens can include prions, which are thought to be a type of infectious pathogenic protein that may cause prion diseases. Prion diseases are degenerative disorders of the nervous system. One such disease, “Mad cow” disease (thought to be a variant of Creutzfeldt-Jakob disease (CJD)), is thought to be caused by a prion present in edible beef from diseased cows. Most cases are sporadic with unknown mode of transmission; some cases are inherited; and a small number have been transmitted by medical procedures. The spread of human prion diseases through consumption of infected material has been implicated historically in kuru and recently in variant CJD. Other animal prion diseases (scrapie of sheep, transmissible mink encephalopathy, chronic wasting disease of cervids, and bovine spongiform encephalopathy) all seem to be laterally transmitted by contact with infected animals or by consumption of infected feed. Risk assessment and predictions of future events pertaining to prion diseases are difficult to ascertain because of the different modes of transmission, the unpredictable species barriers, the variable distribution of infectivity in tissues, and strain variations found in some diseases.

In general, animal products may be exposed to microbial organisms which produce pyrogens (fever-causing substances). Bacterial contaminants of food and/or pharmaceutical products are also a serious issue as evidenced by contamination of food stuffs by enterohemoragic E. coli. Products such as meats derived from cows as well as produce such as apples, spinach, and the like, have been implicated in such contamination. In such cases, it is the toxin produced by the bacteria (rather than the bacteria itself) that produces adverse effects in humans. Such adverse effects include severe diarrhea, kidney failure and in the extreme situations, death. Bacterial endotoxins, a type of pyrogen, must be substantially excluded from all pharmaceutical compositions.

Animal products are generally purified by a process of elimination, i.e., rather than selecting the end-product from a mix, the end product is the material remaining after exclusion of impurities. And, in addition to the potential animal moieties such as pathogens, another artifact of purification from animal sources is that the end-product is a mixture of one or more bile acids. For example, commercial preparations of deoxycholic acid contain some chenodoxycholic acid, as well as cholic acid, which is a precursor to both deoxycholic acid and chenodeoxycholic acid in mammalian bile acid synthesis. Because the exact proportion of deoxy/cheno/cholic is not preselected, this may result in lot-to-lot variation when contemplating manufacturing large amounts of bile acids. Such lot-to-lot variation can be problematic and may engender additional steps in garnering regulatory approvals or quality control, particularly in efforts to produce a pharmaceutical composition. Clearly, producers would desire lot-to-lot predictability in manufacturing bile acid pharmaceutical compositions.

Currently, the concerns regarding animal-derived products containing animal pathogens and other harmful agents has been addressed by sourcing from isolated and inspected animals. For example, deoxycholic acid from animals in New Zealand are a source of bile acids for human use under US regulatory regimes, as long as the animals continue to remain isolated and otherwise free of observable pathogens.

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