Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D405/00—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom
  • C07D405/02—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom containing two hetero rings
  • C07D405/04—Heterocyclic compounds containing both one or more hetero rings having oxygen atoms as the only ring hetero atoms, and one or more rings having nitrogen as the only ring hetero atom containing two hetero rings directly linked by a ring-member-to-ring-member bond
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P1/00—Drugs for disorders of the alimentary tract or the digestive system
  • A61P1/16—Drugs for disorders of the alimentary tract or the digestive system for liver or gallbladder disorders, e.g. hepatoprotective agents, cholagogues, litholytics
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P31/00—Antiinfectives, i.e. antibiotics, antiseptics, chemotherapeutics
  • A61P31/12—Antivirals
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P31/00—Antiinfectives, i.e. antibiotics, antiseptics, chemotherapeutics
  • A61P31/12—Antivirals
  • A61P31/14—Antivirals for RNA viruses
  • A61P31/18—Antivirals for RNA viruses for HIV
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P35/00—Antineoplastic agents
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
  • A61P37/00—Drugs for immunological or allergic disorders
  • A61P37/02—Immunomodulators
  • A61P37/04—Immunostimulants
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D411/00—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen and sulfur atoms as the only ring hetero atoms
  • C07D411/02—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen and sulfur atoms as the only ring hetero atoms containing two hetero rings
  • C07D411/04—Heterocyclic compounds containing two or more hetero rings, at least one ring having oxygen and sulfur atoms as the only ring hetero atoms containing two hetero rings directly linked by a ring-member-to-ring-member bond
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
  • C07H19/00—Compounds containing a hetero ring sharing one ring hetero atom with a saccharide radical; Nucleosides; Mononucleotides; Anhydro-derivatives thereof
  • C07H19/02—Compounds containing a hetero ring sharing one ring hetero atom with a saccharide radical; Nucleosides; Mononucleotides; Anhydro-derivatives thereof sharing nitrogen
  • C07H19/04—Heterocyclic radicals containing only nitrogen atoms as ring hetero atom
  • C07H19/06—Pyrimidine radicals
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
  • C07H19/00—Compounds containing a hetero ring sharing one ring hetero atom with a saccharide radical; Nucleosides; Mononucleotides; Anhydro-derivatives thereof
  • C07H19/02—Compounds containing a hetero ring sharing one ring hetero atom with a saccharide radical; Nucleosides; Mononucleotides; Anhydro-derivatives thereof sharing nitrogen
  • C07H19/04—Heterocyclic radicals containing only nitrogen atoms as ring hetero atom
  • C07H19/06—Pyrimidine radicals
  • C07H19/10—Pyrimidine radicals with the saccharide radical esterified by phosphoric or polyphosphoric acids

Definitions

• This invention is in the area of biologically active nucleosides, and specifically includes antiviral compositions that include 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3- oxathiolane ("FTC”), its physiologically acceptable
• AIDS acquired immune deficiency syndrome
• HIV human immunodeficiency virus
• these synthetic nucleosides are incorporated into a growing strand of viral DNA, causing chain termination due to the absence of the 3'-hydroxyl group.
• ( ⁇ )-dioxolane-T exhibits a modest activity against HIV (EC 50 of 20 ⁇ m in ATH8 cells), and is not toxic to uninfected control cells at a concentration of 200 ⁇ M.
• hepatitis B virus Another virus that causes a serious human health problem is the hepatitis B virus (referred to below as
• HBV is second only to tobacco as a cause of human cancer.
• the mechanism by which HBV induces cancer is
• HBV infection can lead to acute hepatitis and liver damage, that causes abdominal pain, jaundice, and elevated blood levels of certain enzymes. HBV can cause fulminant hepatitis, a rapidly progressive, often fatal form of the disease in which massive sections of the liver are destroyed.
• HBV chronic hepatitis
• Asia alone a chronic carrier of HBV
• worldwide almost 300 million carriers.
• Chronic persistent hepatitis can cause fatigue, cirrhosis of the liver, and hepatocellular
• carcinoma a primary liver cancer.
• HBV infection In western industrialized countries, high risk groups for HBV infection include those in contact with HBV carriers or their blood samples.
• the epidemiology of HBV is very similar to that of acquired immune deficiency syndrome, which accounts for why HBV infection is common among patients with AIDS or AIDS-related complex.
• HBV is more contagious than HIV.
• a human serum-derived vaccine has been developed to immunize patients against HBV. While it has been found effective, production of the vaccine is troublesome because the supply of human serum from chronic carriers is limited, and the purification procedure is long and expensive.
• nucleoside To market a nucleoside for pharmaceutical purposes, it must not only be efficacious with low toxicity, it must also be cost effective to manufacture. An extensive amount of research and development has been directed toward new, low cost processes for large scale nucleoside production. 2',3'- Dideoxynucleosides are currently prepared by either of two routes: derivatization of an intact nucleoside or
• nucleosides that contain either nonnaturally occurring bases or nonnaturally occurring carbohydrate moieties (and which therefore are not prepared from intact nucleosides), such as 1,3-oxathiolane nucleosides and 1,3-dioxolane nucleosides.
• nucleoside a nucleoside is produced that has two chiral centers (at the C1' and C4'-positions), and thus exists as a diastereomeric pair. Each diastereomer exists as a set of enantiomers. Therefore, the product is a mixture of four enantiomers.
• nonnaturally-occurring stereochemistry in either the C1' or the C4'-positions are less active than the same nucleoside with the stereochemistry as set by nature.
• Carter, et al. have reported that the concentration of the (-)-enantiomer of carbovir (2',3'-didehydro-2',3'- dideoxyguanosine) in cell culture required to reduce the reverse transcriptase activity by 50% (EC 50 ) is 0.8 ⁇ M,
• 1,3-oxathiolane nucleosides can be prepared with high diastereoselectivity (high percentage of nucleoside with a ß configuration of the bond from the C1'-carbon to the heterocyclic base) by careful selection of the Lewis acid used in the condensation process. It was discovered that condensation of a 1,3-oxathiolane nucleoside with a base occurs with almost complete ß-stereospecificity when stannic chloride is used as the condensation catalyst. Other Lewis acids provide low (or no) C1'-ß selectivity or simply fail to catalyze the reactions.
• nucleosides prepared by condensing a carbohydrate-like moiety with a base.
• a method and composition for the treatment of HIV and HBV infections in humans and other host animals includes administering an effective amount of 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane, a pharmaceutically acceptable derivative thereof, including a 5' or N 4 alkylated or acylated derivative, or a pharmaceutically acceptable salt thereof, in a
• FTC 2-hydroxymethyl-5-(5- fluorocytosin-1-yl)-1,3-oxathiolane
• FTC and its enantiomers are nontoxic to peripheral human bone marrow cells at concentrations up to 50 ⁇ M and other cell lines at concentrations up to 200 ⁇ M.
• FTC- TP is a major intracellular metabolite in PBMC and HepG2 cells. FTC-TP competitively inhibits HIV-1 reverse
• RT transcriptase
• FTC-TP can be shown to be a potent DNA chain terminator when HIV-RT is used (C-stops).
• Chronic treatment with FTC is not toxic to rodents, even at oral doses of 85 mg/kg per day for at least two months.
• the pharmacokinetics of FTC in rhesus monkeys indicates high oral bioavailability (approximately 73 ⁇ 6%) and a plasma terminal half life of approximately 1.34 ⁇ 0.18 (mean of oral and I.V. administration).
• a process for the resolution of a racemic mixture of nucleoside enantiomers, including the racemic mixture of FTC, is also disclosed that includes the step of exposing the racemic mixture to an enzyme that preferentially catalyzes a reaction in one of the enantiomers.
• the process can be used to resolve a wide variety of nucleosides, including
• the process can also be used to resolve nucleoside derivatives that contain additional heteroatoms in the carbohydrate moiety, for example, ( ⁇ )-FTC and ( ⁇ )-BCH-189.
• the resolution of nucleosides can be performed on large scale at moderate cost.
• FTC was resolved into its (+)-ß-D and (-) -B-L enantiomers.
• the (-)-ß-L- enantiomer appears to be more potent that the (+)-ß-D- enantiomer against HIV, HBV, and SIV.
• the (+)-enantiomer of FTC is also active against HIV, HBV, and SIV.
• FIG. 1 is an illustration of the chemical structure of 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3- oxathiolane ("FTC").
• Figure 2 is an illustration of a method for the preparation of 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane.
• Figure 3 is a flow chart of the specificity of alkaline phosphatase and snake venom phosphodiesterase for the (+) and (-) enantiomers of FTC.
• Figure 4 is a graph indicating the progress of lipase-catalyzed hydrolysis of the 5'-butyryl ester of FTC over time using the enzymes Amano PS-800® (-open square-) and PLE (-open circle with dot-).
• Figure 5 is a graph of the effect of concentration ( ⁇ M) of racemic and enantiomerically enriched FTC (prepared by the method of Example 4) versus the percent inhibition of human PBM cells infected with HIV-1.
• Figure 6 is a graph of the effect of concentration ( ⁇ M) of racemic and enantiomerically enriched FTC (prepared by method of Example 3) on the percent inhibition of human PBM cells infected with HIV-1. ((-darkened circle-, ( ⁇ )-FTC), (-open circle-, (-)-FTCC), (-darkened square-, (+)-FTC) .
• Figure 7 is a graph of the uptake of tritiated ( ⁇ )- FTC in human PBM cells (average of two determinations) in time (hours) versus pmol/10 6 cells.
• Figure 8 is a graph of the egress of radiolabeled ( ⁇ )-FTC from human PBM cells, measured in hours versus pmol/10 6 cells.
• Figure 9 illustrates the presence of [ 3 H]-( ⁇ )-FTC and its phosphorylated derivatives in human HepG-2 cells (average of two determinations) incubated in media containing 10 ⁇ M [ 3 H]-( ⁇ )-FTC, measured in pmol/10 6 cells over time.
• Figure 10 illustrates the egress of [ 3 H]-( ⁇ )-FTC and its phosphorylated derivatives in human HepG2 in pmol/10 6 cells over time cells after pulsing cells with 10 ⁇ M [ 3 H]- ( ⁇ )-FTC (700 DPM/pmole) for 24 hours, and evaluating the concentration of compound 24 hours after removal.
• Figure 11 illustrates the decrease in the combined concentration of [ 3 H]-( ⁇ )-FTC and its phosphorylated
• Figure 12 is a graph of the effect of the
• enantiomerically enriched nucleoside refers to a nucleoside composition that includes at least 95% of a single enantiomer of that nucleoside.
• FTC refers to 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane (the racemic form or enantiomers), also referred to as 2'-deoxy-5-fluoro-3'-thiacytidine.
• the term ( ⁇ )-FTC refers to ( ⁇ )-ß-D.L-2-h ⁇ droxvmethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane.
• the term (-)-FTC refers to (-)-ß-L- 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane.
• (+)-FTC refers to (+)-ß-D- 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane.
• FTC-MP As used herein, the terms FTC-MP, FTC-DP, and FTC- TP refer to the monophosphate, diphosphate, and triphosphate of FTC, respectively.
• BCH-189 refers to 2- hydroxymethyl-5-(cytosin-1-yl)-1,3-oxathiolane.
• preferential enzyme catalysis refers to catalysis by an enzyme that favors one substrate over another.
• a leaving group means a functional group that forms an incipient carbonation when it separates from the molecule that it is attached to.
• the invention as disclosed herein is a method and composition for the treatment of HIV and HBV infections, and other viruses replicating in like manner, in humans or other host animals, that includes administering an effective amount of the ( ⁇ )-ß-D.L. the (-)-ß-L or (+)-ß-D enantiomer of 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane, a pharmaceutically ("physiologically") acceptable derivative, including a 5' or N 4 alkylated or acylated derivative, or a pharmaceutically ("physiologically") acceptable salt thereof, in a pharmaceutically acceptable carrier.
• the compounds of this invention either possess antiretroviral activity, such as anti-HIV-1, anti-HIV-2 and anti-simian immunodeficiency virus (anti-SIV) activity, themselves or are metabolized to a compound that exhibits antiretroviral activity.
• anti-SIV anti-simian immunodeficiency virus
• FTC and its pharmaceutically acceptable derivatives or pharmaceutically acceptable formulations containing these compounds are useful in the prevention and treatment of HIV infections and other related conditions such as AIDS-related complex (ARC), persistent generalized lymphadenopathy (PGL), AIDS-related neurological conditions, anti-HIV antibody positive and HIV-positive conditions, Kaposi's sarcoma, thrombocytopenia purpurea and opportunistic infections.
• these compounds or formulations can be used prophylactically to prevent or retard the progression of clinical illness in individuals who are anti-HIV antibody or HIV-antigen positive or who have been exposed to HIV.
• HBV infections and other related conditions such as anti-HBV antibody positive and HBV-positive
• the present invention includes the following features:
• compositions comprising ( ⁇ )-ß-D.L-2- hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3- oxathiolane, its (-) or (+) enantiomer, or a pharmaceutically acceptable derivative or salt thereof together with a pharmaceutically acceptable carrier;
• R 1a is hydrogen or a hydroxyl protecting group, including an acyl group, and L is a leaving group; and optionally removing any hydroxyl protecting group,
• R 1a is as defined above and R 1b is an amino protecting group
• a fluorinating agent serving to introduce a fluorine atom in the 5-position of the cytosine ring
• enantiomer of 2-hydroxymethyl-5-(5-fluorocytosin-1- yl)-1,3-oxathiolane which comprises subjecting the compound or derivative (e.g. 5'-ester) thereof in the form of a mixture of (-) and (+) enantiomers to conditions or reacting with reagents serving to separate the enantiomers and if necessary converting the resulting derivative to the parent compound.
• the hydroxy protecting group includes protecting groups described in detail below, including acyl (e.g. acetyl), arylacyl (e.g. benzoyl or substituted benzoyl), trityl or monomethoxytrityl, benzyl or substituted benzyl, trisubstituted silyl, including
• trialkylsilyl e.g. dimethyl-t-butylsilyl
• the 5-fluorocytosine compound can be optionally protected with trisubstituted silyl groups.
• the protecting groups can be removed in a conventional manner.
• the leaving group L is a leaving group typical of those known in the art of nucleoside chemistry, e.g. halogen such as chlorine or bromine, alkoxy such as methoxy or ethoxy, or acyl such as acetyl or benzoyl.
• reaction in process e) (i) can be carried out in an organic solvent (e.g., 1,2-dichloroethane or acetonitrile) in the presence of a Lewis acid, preferably stannic chloride, or trimethylsilyl triflate.
• organic solvent e.g., 1,2-dichloroethane or acetonitrile
• Lewis acid preferably stannic chloride, or trimethylsilyl triflate.
• R 1a is defined above
• a reducing agent e.g., lithium aluminum hydride
• a carboxylic acid anhydride e.g. acetic anhydride
• acylation e.g. chlorinating or brominating reagents for halogenation, or alkylating reagents.
• the compound of formula D can be prepared by reaction of a compound of formula E
• the 5-fluoro substituent can be introduced by methods known in the art (M.J. Robins, et al., in Nucleic Acid Chemistry, Part 2, L.B. Townsend and R.S. Tipson, editors, J. Wiley and Sons, New York, 895-900 (19/8) and references therein; R. Duschinsky in Nucleic Acid Chemistry, Part 1, L.B. Townsend and R.S. Tipson, editors, J. Wiley and Sons, New York 43-46 (1978) and references
• the fluorinating agent may be, for example, trimethylhypofluorite in fluorotrichloromethane.
• the compound of formula C can be treated with 1,2,4-triazole, together with 4- chlorophenyl dichlorophosphate, to form the corresponding 4- (1,2,4-triazoylyl) compound which is then converted to the desired 4-amino (cytidine) compound by reaction with for example, methanol.
• FTC can be converted into a pharmaceutically acceptable ester by reaction with an appropriate esterifying agent, for example, an acid halide or anhydride.
• an appropriate esterifying agent for example, an acid halide or anhydride.
• pharmaceutically acceptable derivative can be converted into a pharmaceutically acceptable salt thereof in a conventional manner, for example, by treatment with an appropriate base.
• the ester or salt of FTC can be converted into FTC, for example, by hydrolysis.
• the antivirally active compound disclosed herein is 2-hydroxymethyl-5-(5-fluorocytosin-1-yl)-1,3-oxathiolane (see Figure 1), in the racemic form or as an isolated enantiomer.
• the active compound can be administered as any derivative that upon administration to the recipient, is capable of providing directly or indirectly, the parent FTC compound, or that exhibits activity itself.
• Nonlimiting examples are the pharmaceutically acceptable salts
• the acyl group is a carboxylic acid ester in which the non-carbonyl moiety of the ester group is selected from straight, branched, or cyclic alkyl,
• triphosphate ester trityl or monomethoxytrityl, substituted benzyl, trialkylsilyl (e.g. dimethyl-t-butylsilyl) or
• Aryl groups in the esters optimally comprise a phenyl group.
• the alkyl group can be straight, branched, or cyclic, and is optimally a C, to C 18 group.
• compositions of FTC include, but are not limited to:
• R, and R 2 are independently selected from the group consisting of alkyl and acyl, specifically including but not limited to methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, sec-butyl, t-butyl, isopentyl, amyl, t-pentyl, 3-methylbutyryl, hydrogen succinate, 3- chlorobenzoate, cyclopentyl, cyclohexyl, benzoyl, acetyl, pivaloyl, mesylate, propionyl, butyryl, valeryl, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, oleic, amino acids including but not limited to alanyl, valinyl, leucinyl, isoleucinyl, prolinyl, phenylalaninyl,
• R 1 and R 2 can be H.
• FTC or its derivatives can be provided in the form of pharmaceutically acceptable salts.
• pharmaceutically acceptable salts or complexes refers to salts or complexes of FTC that retain the desired biological activity of the parent compound and exhibit minimal, if any, undesired toxicological effects.
• Nonlimiting examples of such salts are (a) acid addition salts formed with inorganic acids (for example, hydrochloric acid, hydrobromic acid, sulfuric acid, phosphoric acid, nitric acid, and the like), and salts formed with organic acids such as acetic acid, oxalic acid, tartaric acid, succinic acid, malic acid,
• ascorbic acid benzoic acid, tannic acid, pamoic acid,
• alginic acid polyglutamic acid, naphthalenesulfonic acids, naphthalenedisulfonic acids, and polygalacturonic acid;
• base addition salts formed with polyvalent metal cations such as zinc, calcium, bismuth, barium, magnesium, aluminum, copper, cobalt, nickel, cadmium, sodium, potassium, and the like, or with an organic cation formed from N,N-dibenzylethylene-diamine, ammonium, or ethylenediamine; or
• Modifications of the active compound can affect the bioavailability and rate of metabolism of the active species, thus providing control over the delivery of the active species. Further, the modifications can affect the antiviral activity of the compound, in some cases increasing the activity over the parent compound. This can easily be assessed by preparing the derivative and testing its antiviral activity according to the methods described herein, or other method known to those skilled in the art.
• 1,4-dibutyryl-2-butene-1,4-diol is a colorless to slightly yellow, clear liquid.
• 1,4-Dibutyryl-2-butene-1,4-diol (1.365 mol) was dissolved. in 4L of dry CH 2 Cl 2 in a dry, 5L 3-neck flask
• the tube is optimally not a fritted, gas bubbling tube that will clog on exposure to the
• the ozone was then introduced at 8 to 8.5 psi. Upon completion, the ozone flow was stopped, and oxygen was bubbled through the solution for about a half an hour before 3 equivalents of Me 2 S were added. The flask was removed from the cooling bath and transported to a hood where it was stirred for about 2 days to affect complete reduction. The solution was evaporated and put under vacuum for several hours.
• This reaction typically yields approximately 95% of protected aldehyde (2-butyryloxyacetaldehyde), a colorless to yellow, clear liquid.
• the aldehyde (1.0 equivalent) was dissolved in toluene to provide a 0.80 to 0.85M solution in a flask equipped with a Dean Stark-type trap.
• Thioglycolic acid (1.1 equiv.) was added and the mixture was heated to reflux.
• the reaction typically provides a 90% yield of 2- (butyryloxy)-methyl-5-oxo-1,3-oxathiolane.
• Prog, rate - 10o/min; Final T - 240oC) typically indicates a purity of approximately 70%.
• 5-Fluorocytosine (1.05 equivalents based on amount of acetylated lactol obtained in the previous step using GC indication of purity) was silylated by reflux in at least 10 equivalents of hexamethyldisilazane containing a catalytic amount of pure ammonium sulfate (0.05 to 0.10 eq.) for two hours after the solution turned clear.
• the flask was then sealed tightly and the solvent removed using a vacuum pump with an auxiliary trap.
• reaction solution was stirred for 2 hours, at which point the completion of reaction was indicated by TLC.
• the reaction solution was then diluted with dichloromethane (500 ml) and quenched with ammonium hydroxide solution.
• the ammonium hydroxide solution (100 ml) was added slowly
• FTC-5'-butyrate (8.74 gm; 0.026 mol) was dissolved in 250 ml methanol. Sodium methoxide (2.85 gm; 0.052 gm) was added at room temperature. The reaction was stirred for 1 hour, at which point the completion of reaction was confirmed by TLC. NH 4 Cl solution (10 ml) was added to quench the reaction, and then the solvent was removed under reduced pressure. The residue was absorbed on silica gel (5gm) and passed through a small column using ethyl acetate:ethanol as an eluent (9:1). The product-containing fractions were combined and evaporated to give a sticky solid which was washed with dry ether to give white solid FTC (6.00 gm, 88%).
• a method for the resolution of racemic mixtures of nucleoside enantiomers, including but not limited to the (+) and (-) enantiomers of FTC.
• the method can also be used to resolve racemic mixtures of carbohydrates or carbohydrate-like moieties, such as derivatives of 1,3-oxathiolane and 1,3-dioxolane.
• the method involves the use of an enzyme that preferentially catalyzes a reaction of one enantiomer in a racemic mixture. The reacted enantiomer is separated from the unreacted enantiomer on the basis of the new difference in physical structure.
• the method includes reacting the C5*-hydroxyl group of a mixture of nucleoside racemates with an acyl compound to form C5'-esters in which the nucleoside is in the "carbinol" end of the ester.
• the racemic mixture of nucleoside C5'-esters is then treated with an enzyme that preferentially cleaves, or hydrolyses, one of the enantiomers and not the other, in a given time period.
• An advantage of this method is that it can be used to resolve a wide variety of nucleosides, including
• the method can also be used to resolve nucleoside derivatives that contain additional heteroatoms in the carbohydrate moiety, for example, FTC and BCH-189.
• Another advantage of this method is that it is regioselective. Enzymes that hydrolyse esters typically do not catalyze extraneous reactions in other portions of the molecule. For example, the enzyme lipase catalyses the hydrolysis of the ester of 2-hydroxymethyl-5-oxo-1,3- oxathiolane without hydrolysing the internal lactone. This contrasts markedly with "chemical" approaches to ester hydrolysis.
• Still another advantage of this method is that the separation of the unhydrolysed enantiomer and the hydrolysed enantiomer from the reaction mixture is quite simple.
• the unhydrolysed enantiomer is more lipophilic than the
• hydrolysed enantiomer and can be efficiently recovered by simple extraction with one of a wide variety of nonpolar organic solvents or solvent mixtures, including hexane and hexane/ether.
• the less lipophilic, more polar hydrolysed enantiomer can then be obtained by extraction with a more polar organic solvent, for example, ethyl acetate, or by lyophilization, followed by extraction with ethanol or methanol.
• Alcohol should be avoided during the hydrolysis because it can denature enzymes under certain conditions.
• nucleoside enantiomer With the proper matching of enzyme and substrate, conditions can be established for the isolation of either nucleoside enantiomer.
• the desired enantiomer can be
• Enzymes that catalyze the hydrolysis of esters include esterases, for example pig liver esterase, Upases, including porcine pancreatic lipase and Amano PS-800 lipase, substillisin, and ⁇ -chymotrypsin.
• Figure 3 is a flow chart of the specificity of alkaline phosphatase and snake venom phosphodiesterase for the (+) and (-) enantiomers of FTC.
• alkaline phosphatase hydrolyses the triphosphate of both of the enantiomers to FTC, and therefore is not effective as a separation means.
• Phosphodiesterase I preferentially
• the most effective acyl group to be used to esterify the C5'-position of the nucleoside can be determined without undue experimentation by evaluation of a number of homologs using the selected enzyme system. For example, when 1,3- oxathiolane nucleosides are esterified with butyric acid, resolutions with both pig liver esterase and Amano PS-800 proceed with high enantioselectivity (94-100% enantiomeric excess) and opposite selectivity.
• Pig liver esterase 1,3- oxathiolane nucleosides are esterified with butyric acid
• the percent enantiomeric excess reported in Table 1 is the amount of purified butyrate ester remaining in the enzyme treated mixture (i.e., the butyrate ester of (-)-FTC in the case of PLE and the butyrate ester of (+)-FTC in the case of Amano PS-800).
• Non-limiting examples of acyl groups that can be evaluated for use with a particular nucleoside enantiomeric mixture and particular enzyme include alkyl carboxylic acids and substituted alkyl carboxylic acids, including acetic acid, propionic acid, butyric acid, and pentanoic acid. With certain enzymes, it may be preferred to use an acyl compound that is significantly electron-withdrawing to facilitate hydrolysis by weakening the ester bond.
• electron-withdrawing acyl groups include ⁇ -haloesters such as 2-chloropropionic acid, 2-chlorobutyric acid, and 2- chloropentanoic acid. ⁇ -Haloesters are excellent substrates for lipases.
• the enzymatic hydrolyses are typically carried out with a catalytic amount of the enzyme in an aqueous buffer that has a pH that is close to the optimum pH for the enzyme in question. As the reaction proceeds, the pH drops as a result of liberated carboxylic acid. Aqueous base should be added to maintain the pH near the optimum value for the enzyme. The progress of the reaction can be easily
• the hydrophobic ester (the unhydrolysed enantiomer) and the more polar alcohol (the hydrolysed enantiomer) can be sequentially and selectively extracted from the solution by the judicious choice of organic solvents.
• the material to be resolved can be passed through a column that contains the enzyme immobilized on a solid support.
• Enzymatic hydrolyses performed under heterogeneous conditions can suffer from poor reproducibility. Therefore, it is preferred that the hydrolysis be performed under homogeneous conditions. Alcohol solvents are not preferred because they can denature the enzymes. Homogeneity can be achieved through the use of non-ionic surfactants, such as Triton X-100. However, addition of these surfactants not only assists in dissolving the starting material, they also enhance the aqueous solubility of the product. Therefore, although the enzymatic reaction can proceed more effectively with the addition of a non-ionic surfactant than under heterogeneous conditions, the isolation of both the recovered starting material and the product can be made more difficult. The product can be isolated with appropriate chromatographic and chemical (e.g., selective salt formation) techniques. Diacylated nucleosides can be used but are often quite lipophilic and hard to dissolve in the medium used.
• a number of 5'-O-acyl derivatives of FTC were prepared by selective O-acylation of the N-hydrochloride salt (see Table 1 and Figure 4) of ( ⁇ )-FTC.
• the efficiency of the hydrolysis of the derivatives by lipases was investigated.
• pig liver esterase (PLE) exhibits a high level of selectivity for the hydrolysis of the ester of the (+)-enantiomer of FTC, leaving predominately the butyrate of (-)-FTC in the HPLC-analyzed mixture.
• PS-800 hydrolyses the ester of the (-)-enantiomer of FTC
• Example 3 Procedure for the Preparation of (+)- and (-)-FTC via Enantioselective, Lipase-Catalyzed Hydrolysis of FTC Butyrate.
• reaction mixture was extracted with 2 ⁇ 80 mL of CHCI 3 and 80 mL of ethyl acetate.
• organic layer extracts were combined, dried over anhydrous MgS0 4 , filtered, and concentrated by rotary evaporation. The resulting
• Emulsions in the work-up step can be avoided by adding HCCI 3 to the reaction mixture on completion (which also serves to denature the enzyme), stripping the solvents under vacuum, and then extracting with HCCI 3 .
• (+)-FTC was isolated as a white solid (109 mg; 37% based on starting butyrate) .
• cytidine-deoxycytidine deaminase is used to resolve racemic mixtures of 2- hydroxymethyl-5-(cytosin-1-yl)-1,3-oxathiolane and its derivatives, including 2-hydroxymethyl-5-(5-fluoro-cytosin- 1-yl)-1,3-oxathiolane.
• the enzyme catalyses the deamination of the cytosine moiety to a uracil. It has been discovered that one of the enantiomers of 1,3-oxathiolane nucleosides is a preferred substrate for cytidine-deoxycytidine deaminase.
• the enantiomer that is not converted to a uracil derivative (and therefore is still basic) is extracted from the solution with an acidic solution. Care should be taken to avoid strong acidic solutions (pH below 3.0), that may cleave the oxathiolane ring.
• Cytidine-deoxycytidine deaminase can be isolated from rat liver or human liver, or expressed from recombinant sequences in a procaryotic system such as in E. coli .
• the method of resolution of cytidine nucleoside enantiomers using cytidine-deoxycytidine deaminase can be used as the sole method of resolution or can be used in combination with other methods of resolution, including resolution by enzymatic hydrolysis of 5'-O-nucleoside esters as described above.
• Recrystallization based on the principle that racemates are often more soluble than the corresponding individual enantiomers. Recrystallization can be performed at any stage, including on the acylated
• nucleoside is basic (for example, a cytidine) one can use chiral acids that form diastereomeric mixtures that may possess significantly different solubility properties.
• Nonlimiting examples of chiral acids include malic acid, mandelic acid, dibenzoyl tartaric acid, 3-bromocamphor-8- sulfonic acid, 10-camphorsulfonic acid, and di-p- toluoyltartaric acid.
• acylation of the free hydroxyl group with a chiral acid derivative also results in the formation of diastereomeric mixtures whose physical properties may differ sufficiently to permit separation.
• enantiomerically enriched nucleosides can be obtained or purified by passing the racemic mixture through an HPLC column that has been designed for chiral separations, including cyclodextrin bonded columns marketed by Rainin Corporation.
• Example 4 Separation of Racemic Mixtures of Nucleosides by HPLC.
• nucleosides it is often desirable to screen a number of racemic mixtures of nucleosides as a preliminary step to determine which warrant further resolution into enantiomerically enriched components and further evaluation of antiviral activity.
• the ability of nucleosides to inhibit HIV can be measured by various experimental techniques. The technique used herein, and described in detail below, measures the inhibition of viral replication in phytohemagglutinin (PHA) stimulated human peripheral blood mononuclear (PBM) cells infected with HIV-1 (strain LAV). The amount of virus produced is determined by measuring the virus-coded reverse transcriptase enzyme. The amount of enzyme produced is proportional to the amount of virus produced.
• Table 3 provides the EC 50 values (concentration of nucleoside that inhibits the replication of the virus by 50% in PBM cells, estimated 10% error factor) and IC 50 values (concentration of nucleoside that inhibits 50% of the growth of mitogen- stimulated uninfected human PBM cells) of a number of ( ⁇ )- 1,3-oxathiolane and nucleosides.
• AZT was used as a positive control.
• HIV-1 strain LAV was obtained from the Center for Disease Control, Atlanta,
• transcriptase activity were those described by McDougal et al. (J. Immun. Meth. 76, 171-183, 1985) and Spira et al. (J. Clin. Meth. 25, 97-99, 1987), except that fungizone was not included in the medium (see Schinazi, et al., Antimicrob. Agents Chemother. 32, 1784-1787 (1988); Id., 34:1061-1067 (1990)).
• the median effective (EC 50 ) concentration was determined by the median effect method (Antimicrob. Agents Chemother. 30, 491-498 (1986). Briefly, the percent
• the EC 50 is the concentration of compound at which there is a 50% inhibition of viral growth.
• the substituted cytosine 1,3-oxathiolane nucleosides are more active than the corresponding uracil nucleosides.
• the error in EC 50 and IC 50 measurements are estimated at ⁇ 10%.
• DLS-022 compound 8
• exceptional activity approximately 10 nM in PBM cells
• quite low toxicity >100 ⁇ M in PBM, Vero and CEM cells.
• the IC 50 of ( ⁇ )-FTC was over 100 ⁇ M, indicating that the compound was not toxic in uninfected PBM cells evaluated up to 100 ⁇ M.
• Example 8 Antiviral Activity of FTC Enantiomers Resolved by Method of Example 3.
• Figure 7 is a graph of the presence (uptake) of tritiated ( ⁇ )-FTC in human PBM cells (average of two
• the antiretroviral activity of FTC was measured in a number of cell lines using procedures similar, but not identical, to that set out in Example 6.
• Cell lines were obtained from either human donors, AIDS Research and
• the CEM thymidine kinase deficient cells were prepared by sequential passage of CEM cells in the presence of 5-bromo-2'-deoxyuridine. The results are provided in Table 5.
• Figure 8 is a graph of the egress of radiolabeled ( ⁇ )-FTC from human PBM cells, measured in hours after drug removal versus concentration (pmol/10 6 cells).
• FTC-triphosphate has an intracellular half- life of approximately 12 hours and can be easily detected intracellularly at concentrations of 1-5 ⁇ M 48 hours after the removal of the extracellular drug, which is well above the EC 50 for the compound.
• affinity (K 1 ) for ( ⁇ )-FTC triphosphate using HIV RT is 0.2 ⁇ M, which is below the 48 hour concentration level.
• Antiviral Res. 15:217). The antiviral evaluations were performed on two separate passages of cells. All wells, in all plates, were seeded at the same density and at the same time.
• depressions greater than 3.5-fold (for HBV virion DNA) or 3.0-fold (for HBV DNA replication intermediates) from the average levels for these HBV DNA forms in untreated cells are considered to be statistically significant [P ⁇ 0.05].
• the levels of integrated HBV DNA in each cellular DNA preparation (which remain constant on a per cell basis in these experiments) were used to calculate the levels of intracellular HBV DNA forms, thereby ensuring that equal amounts of cellular DNA were compared between separate samples.
• Typical values for extracellular HBV virion DNA in untreated cells ranged from 50 to 150 pg/ml culture medium (average of approximately 76 pg/ml).
• Intracellular HBV DNA replication intermediates in untreated cells ranged from 50 to 100 pg/ ⁇ g cell DNA (average approximately 74 pg/ ⁇ g cell DNA).
• HBV virion DNA due to treatment with antiviral compounds are less pronounced, and occur more slowly, than depressions in the levels of HBV virion DNA (Korba and
• Toxicity analyses were performed to assess whether any observed antiviral effects were due to a general effect on cell viability.
• the method used herein was the
• test compounds As indicated in Table 6, no significant toxicity (greater than 50% depression of the dye uptake levels observed in untreated cells) was observed for the test compounds at the concentrations used for the antiviral evaluations. Both test compounds, (-)-FTC and (+)-FTC, appeared to be toxic at the highest concentration used for the toxicity tests (330 ⁇ M).
• HBV virion DNA and intracellular HBV replication intermediates [HBV RI] remained constant in the untreated cells over the challenge period.
• DMSO at a concentration of 1%, did not affect the levels of HBV replication in 2.2.15 cell cultures.
• HBV virion DNA significantly inhibits the synthesis of HBV virion DNA and intracellular HBV DNA at concentrations of 4, 1, and 0.25 ⁇ M.
• Intracellular HBV DNA was analyzed 24 hours following the 9th day of treatment.
• the levels of integrated HBV DNA in each cell DNA preparation were used to calculate the levels of episomal 3.2Kb HBV genomes (MONO.) and HBV DNA replication intermediates (RI).
• HBV VIRION DNA* INTRACELLULAR HBV (pg/ml CULTURE MEDIUM) (pg/ ⁇ g CELL DNA)
• Sensitivity cutoff for HBV virion DNA was 0.1 pg/ml.
• HBV DNA replication intermediates Analysis of intracellular HBV DNA was 24 hours following the 9th day of treatment.
• the levels of integrated HBV DNA in each cell DNA preparation were used to calculate the levels of episomal 3.2 kb HBV genomes (MONO.) and HBV DNA replication intermediates (RI).
• Example 14 Uptake of ( ⁇ )-FTC into Human Liver Cells; HVB Activity of FTC.
• Example 9 The procedure of Example 9 was repeated with human liver cells (HepG2 cells, available from the ATCC) to determine the uptake and metabolism of FTC in these cells. As shown in Figure 9, ( ⁇ )-FTC is taken up by HepG2 cells in large amounts. These human liver cells metabolize a large percentage of the ( ⁇ )-FTC to ( ⁇ )-FTC triphosphate.
• human liver cells HepG2 cells, available from the ATCC
• Figure 10 illustrates the egress of [ 3 H]-( ⁇ )-FTC and its phosphorylated derivatives in human HepG2 in pmol/10 6 cells over time cells after pulsing cells with 10 ⁇ M [ 3 H]- ( ⁇ )-FTC (700 DPM/pmole) for 24 hours, and evaluating the concentration of compound 24 hours after removal.
• Figure 11 illustrates the decrease in the combined concentration of [ 3 H]-( ⁇ )-FTC and its phosphorylated
• Figure 12 is a graph of the effect of the (-) and (+) enantiomers of FTC on colony formation of granulocytes-macrophage precursor cells, as measured in percent survival versus concentration in ⁇ M ((-)-FTC, open circle; (+)-FTC, darkened circle; AZT, darkened square.
• the (-)-enantiomer of FTC appears to be less toxic, i.e., have a higher IC 50 , than either the (+) -enantiomer or AZT in this cell line.
• ( ⁇ )-FTC was administered intravenously at dosages of 10, 50 and 100 mg/kg to rats, and the area under the plasma drug concentration versus time (AUC), total clearance (CL T ), steady-state volume of distribution (V ss ), mean
• AUC area under the plasma drug concentration versus time curve
• CL total clearance
• V ss steady-state volume of distribution
• MRT mean residence time
• t 1/2 half-life.
• Model-independent pharmacokinetic parameters were derived for ( ⁇ )-FTC by administration (intravenous (I.V.) and oral (P.O.)) of 33.3 mg/kg to rhesus monkeys.
• I.V. intravenous
• P.O. oral
• bioavailability of the compound in monkeys was 73% ( ⁇ 6%).
• K a first order absorption rate constant.
• Humans suffering from diseases caused by HIV or HBV infection can be treated by administering to the patient an effective amount of ( ⁇ )-FTC, or its (-) or (+) enantiomer or a pharmaceutically acceptable derivative or salt thereof in the presence of a pharmaceutically acceptable carrier or diluent.
• the active materials can be administered by any appropriate route, for example, orally, parenterally, intravenously, i ⁇ tradermally, subcutaneously, or topically, in liquid or solid form.
• the active compound is included in the pharmaceutically acceptable carrier or diluent in an amount sufficient to deliver to a patient a therapeutically effective amount of compound to inhibit viral replication in vivo, especially HIV and HBV
• inhibitory amount is meant an amount of active ingredient sufficient to exert an inhibitory effect as measured by, for example, an assay such as the ones described herein.
• a preferred dose of (-), (+), or ( ⁇ )-FTC for all of the above-mentioned conditions will be in the range from about 1 to 50 mg/kg, preferably 1 to 20 mg/kg, of body weight per day, more generally 0.1 to about 100 mg per kilogram body weight of the recipient per day.
• pharmaceutically acceptable derivatives can be calculated based on the weight of the parent nucleoside to be delivered. If the derivative exhibits activity in itself, the effective dosage can be estimated as above using the weight of the derivative, or by other means known to those skilled in the art.
• the compound is conveniently administered in unit any suitable dosage form, including but not limited to one containing 7 to 3000 mg, preferably 70 to 1400 mg of active ingredient per unit dosage form.
• a oral dosage of 50-1000 mg is usually
• the active ingredient should be administered achieve peak plasma concentrations of the active compound of from about 0.2 to 70 ⁇ M, preferably about 1.0 to 10 ⁇ M. This may be achieved, for example, by the intravenous injection of a 0.1 to 5% solution of the active ingredient, optionally in saline, or administered as a bolus of the active ingredient.
• the concentration of active compound in the drug composition will depend on absorption, inactivation, and excretion rates of the drug as well as other factors known to those of skill in the art. It is to be noted that dosage values will also vary with the severity of the condition to be alleviated. It is to be further understood that for any particular subject, specific dosage regimens should be adjusted over time according to the individual need and the professional judgment of the person
• compositions and that the concentration ranges set forth here are exemplary only and are not intended to limit the scope or practice of the claimed composition.
• the active ingredient may be administered at once, or may be divided into a number of smaller doses to be administered at varying intervals of time.
• compositions will generally include an inert
• the active compound can be any suitable pharmaceutically acceptable carrier. They may be enclosed in gelatin capsules or compressed into tablets.
• the active compound can be
• the tablets, pills, capsules, troches and the like can contain any of the following ingredients, or compounds of a similar nature: a binder such as microcrystalline cellulose, gum tragacanth or gelatin; an excipient such as starch or lactose, a disintegrating agent such as alginic acid, Primogel, or corn starch; a lubricant such as magnesium stearate or Sterotes; a glidant such as colloidal silicon dioxide; a sweetening agent such as sucrose or saccharin; or a flavoring agent such as peppermint, methyl salicylate, or orange flavoring.
• a binder such as microcrystalline cellulose, gum tragacanth or gelatin
• an excipient such as starch or lactose, a disintegrating agent such as alginic acid, Primogel, or corn starch
• a lubricant such as magnesium stearate or Sterotes
• a glidant such as colloidal silicon dioxide
• ( ⁇ )-FTC or its (-) or (+)-enantiomer or pharmaceutical acceptable derivatives or salts thereof can be administered as a component of an elixir, suspension, syrup, wafer, chewing gum or the like.
• a syrup may contain, in addition to the active
• preservatives dyes and colorings and flavors.
• pharmaceutically acceptable derivatives or salts thereof can also be mixed with other active materials that do not impair the
• intradermal, subcutaneous, or topical application can include the following components: a sterile diluent such as water for
• antibacterial agents such as benzyl alcohol or methyl parabens
• antioxidants such as ascorbic acid or sodium bisulfite
• chelating agents such as ethylenediaminetetraacetic acid
• buffers such as acetates, citrates or phosphates and agents for the adjustment of tonicity such as sodium chloride or dextrose.
• the parental preparation can be enclosed in ampoules, disposable syringes or multiple dose vials made of glass or plastic.
• preferred carriers are physiological saline or phosphate buffered saline (PBS).
• the active compounds are prepared with carriers that will protect the compound against rapid elimination from the body, such as a controlled release formulation, including implants and microencapsulated delivery systems.
• a controlled release formulation including implants and microencapsulated delivery systems.
• Biodegradable, biocompatible polymers can be used, such as ethylene vinyl acetate, polyanhydrides, polyglycolic acid, collagen, polyorthoesters, and polylactic acid. Methods for preparation of such formulations will be apparent to those skilled in the art. The materials can also be obtained commercially from Alza Corporation and Nova Pharmaceuticals, Inc.
• Liposomal suspensions are also preferred as pharmaceutically acceptable carriers. These be prepared according to methods known to those skilled in the art, for example, as described in U.S. Patent No. 4,522,811 (which is incorporated herein by reference in its entirety). For
• liposome formulations may be prepared by dissolving appropriate lipid(s) (such as stearoyl phosphatidyl ethanolamine, stearoyl phosphatidyl choline, arachadoyl phosphatidyl choline, and cholesterol) in an inorganic solvent that is then evaporated, leaving behind a thin film of dried lipid on the surface of the container.
• appropriate lipid(s) such as stearoyl phosphatidyl ethanolamine, stearoyl phosphatidyl choline, arachadoyl phosphatidyl choline, and cholesterol
• an inorganic solvent that is then evaporated, leaving behind a thin film of dried lipid on the surface of the container.
• An aqueous solution of the active compound or its monophosphate, diphosphate, and/or triphosphate derivatives are then introduced into the container.
• the container is then swirled by hand to free lipid material from the sides of the container and to disperse
• Mono, di, and triphosphate derivative of FTC can be prepared as described below.
• the monophosphate can be prepared according to the procedure of Imai et al., J. Org. Chem., 34(6), 1547-1550 (June 1969). For example, about 100 mg of FTC and about 280 ⁇ l of phosphoryl chloride are reacted with stirring in about 8 ml of dry ethyl acetate at about 0oC for about four hours. The reaction is quenched with ice. The aqueous phase is purified on an activated charcoal column, eluting with 5% ammonium hydroxide in a 1:1 mixture of ethanol and water. Evaporation of the eluant gives ammonium FTC-5'-monophosphate.
• the diphosphate can be prepared according to the procedure of Davisson et al., J. Org. Chem., 52(9), 1794-1801 (1987).
• FTC diphosphate can be prepared from the corresponding tosylate, that can be prepared, for example, by reacting the nucleoside with tosyl chloride in pyridine at room temperature fo about 24 hours, working up the product in the usual manner (e.g., by washing, drying, and crystallizing it).
• the triphosphate can be prepared according to the procedure of Hoard et al., J. Am. Chem. Soc.. 87(8), 1785-1788 (1965).
• FTC is activated (by making a imidazolide, according to methods known to those skilled in the art) and treating with .tributyl ammonium pyrophosphate in DMF.
• the reaction gives primarily the triphosphate of the nucleoside, with some unreacted monophosphate and some diphosphate. Purification by anion

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