HK1005542B - 1,3-oxathiolanes useful in the treatment of hepatitis - Google Patents

Description

The present invention relates to the use of nucleoside analogues in the treatment of viral infections. More specifically it is concerned with the use of 1,3-oxathiolane nucleoside analogues in the treatment of hepatitis, in particular hepatitis B.

Hepatitis B is a viral disease transmitted orally or parenterally by contaminated material such as blood and blood products, contaminated needles, sexually and vertically from infected or carrier mothers to their off-spring. In those areas of the world where the disease is common, vertical transmission at an early age results in a high proportion of infected individuals becoming chronic carriers of hepatitis B. There are an estimated 280,000,000 carriers of hepatitis B worldwide. At the present time there are no effective chemotherapeutic agents for the treatment of hepatitis B infections.

International patent publications WO 90/14079 and WO 90/14091, both published on November 29, 1990, describe certain 2',3'-dideoxynucleosides (specifically ddG, ddA, ddI and ddC) as effective in the treatment of both HIV and HBV infections.

European patent publication 0382526A describes a series of 1,3-oxathiolane nucleoside analogues having antiviral activity, in particular activity against HIV, the causative agent of AIDS. We have now found that certain of the compounds described in EP 0382526A are active both in vitro and in vivo against the hepatitis B virus.

International Patent Publication WO 92/15308 entitled "Use of 5-fluoro-2'-deoxy-3'-thia-cytidine for the treatment of Hepatitis B" discloses that 5-fluoro-2'-deoxy-3'-thiacytidine (FTC) and physiologically functional derivatives thereof have potent activity against HBV. WO 92/15308 forms part of the state of the art under Art. 54(3) EPC.

The present invention provides the use for the manufacture of a medicament for the treatment of hepatitis B infection of a compound of formula (I) or a pharmaceutically acceptable derivative thereof wherein Z is S, S=0 or SO₂; R₁ is hydrogen or an acyl; R₂ is: R₃ is selected from hydrogen, unsubstituted C_1-6 alkyl, and C_1-6 alkyl substituted with a heteroatom; R₄ and R₅ are each independently selected from hydrogen, C_1-6 alkyl, bromine, chlorine, fluorine and iodine; R₆ is selected from hydrogen, CN, carboxy, ethoxycarbonyl, carbamoyl and thiocarbamoyl; and X and Y are independently selected from bromine, chlorine, fluorine, iodine, amino and hydroxy groups; provided that: R₂ is not cytosine or 5-F-cytosine when Z is S.

In another aspect the invention provides the use for the manufacture of a medicament for the treatment of hepatitis B infection of a compound selected from:

• cis-2-benzoyloxymethyl-5-(cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, trans-2-benzoyloxymethyl-5-(cytoein-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, and mixtures thereof;
• cis-2-hydroxymethyl-5-(N4'-acetyl-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, trans-2-hydroxymethyl-5-(N4'-acetyl-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, and mixtures thereof;
• cis-2-benzyloylmethyl-5-(N4'-acetyl-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, trans-2-benzyloylmethyl-5-(N4'-acetyl-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, and mixtures thereof;
• cis-2-benzyloylmethyl-5-(N4'-acetyl-5-fluoro-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, trans-2-benzyloylmethyl-5-(N4'-acetyl-5-fluoro-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, and mixtures thereof;
• cis-2-hydroxymethyl-5-(cytosin-1'-yl)-3-oxo-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer;
• cis-2-hydroxymethyl-5-(thymin-N-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer;
• cis-2-hydroxymethyl-5-(N,N-dimethylaminomethylene cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer;
• and pharmaceutically acceptable salts thereof.

In a further aspect the invention provides the use for the manufacture of a medicament for the treatment of hepatitis B infections of a compound selected from:

1. 1) cis-2-hydroxymethyl-5-(5'-fluorocytosin-1'-yl)-1,3-oxathiolane or a pharmaceutically acceptable salt thereof, in the form of a racemic mixture or a single enantiomer,
2. 2) trans-2-hydroxymethyl-5-(5'-fluorocytosin-1'-yl)-1,3-oxathiolane or a pharmaceutically acceptable salt thereof, in the form of a racemic mixture or a single enantiomer, and
3. 3) mixtures thereof;

at least one other therapeutically active antiviral agent; and optionally, a pharmaceutically acceptable carrier.

It will be appreciated by one of skill in the art that when R₁ is an acyl group, the compounds of formula (I) are esters. Preferred esters include a carboxyl function R-CO-O in which the non-carbonyl moiety R is selected from hydrogen, straight or branched chain alkyl (e.g. methyl, ethyl, n-propyl, t-butyl, n-butyl), alkoxyalkyl (e.g., methoxymethyl), aralkyl (e.g. benzyl), aryloxyalkyl (e.g. phenoxymethyl), aryl (e.g. phenyl optionally substituted by halogen, C_1-4 alkyl or C_1-4 alkoxy); substituted dihydro pyridinyl (e.g. N-methyldihydro pyridinyl); sulphonate esters such as alkyl- or aralkylsulphonyl (e.g. methanesulphonyl); sulfate esters, amino acid esters (e.g. L-valyl or L-isoleucyl) and mono-, di- or tri-phosphate esters.

Also included within the scope of such esters are esters derived from polyfunctional acids such as carboxylic acids containing more than one carboxyl group, for example, dicarboxylic acids HO₂C(CH₂)_nCO₂H where n is an integer of 1 to 10 (for example, succinic acid) or phosphoric acids. Methods for preparing such esters from the corresponding alcohol are well known. See, for example, Hahn et al., "Nucleotide Dimers as Anti Human Immunodeficiency Virus Agents", Nucleotide Analogues, pp. 156-159 (1989) and Busso et al., "Nucleotide Dimers Suppress HIV Expression In Vitro", AIDS Research and Human Retroviruses, 4(6), pp. 449-455 (1988).

With regard to the above described esters, unless otherwise specified, any alkyl moiety present advantageously contains 1 to 16 carbon atoms, particularly 1 to 4 carbon atoms and could contain one or more double bonds. Any aryl moiety present in such esters advantageously comprises a phenyl group.

In particular the esters may be a C_1-16 alkyl ester, an unsubstituted benzoyl ester or a benzoyl ester substituted by at least one halogen (bromine, chlorine, fluorine or iodine), C_1-6 alkyl, saturated or unsaturated C_1-6 alkoxy, nitro or trifluoromethyl groups. In more detail, by the term "pharmaceutically acceptable derivative" is meant any pharmaceutically acceptable salt of a compound of formula (I).

It will be appreciated by those skilled in the art that the compounds of formula (I) may be modified to provide pharmaceutically acceptable derivatives thereof, at functional groups in both the base moiety and at the oxathiolane ring.

Pharmaceutically acceptable salts of the compounds of formula (I) include those derived from pharmaceutically acceptable inorganic and organic acids and bases. Examples of suitable acids include hydrochloric, hydrobromic, sulphuric, nitric, perchloric, fumaric, maleic, phosphoric, glycollic, lactic, salicylic, succinic, toluene-p-sulphonic, tartaric, acetic, citric, methanesulphonic, formic, benzoic, malonic, naphthalene-2-sulphonic and benzenesulphonic acids. Other acids such as oxalic, while not in themselves pharmaceutically acceptable, may be useful in the preparation of salts useful as intermediates in obtaining the compounds of the invention and their pharmaceutically acceptable acid addition salts.

Salts derived from appropriate bases include alkali metal (e.g., sodium), alkaline earth metal (e.g., magnesium), ammonium and NR₄+ (where R is C_1-4 alkyl) salts.

References hereinafter to a compound according to the invention includes both the compound of formula (I) and its pharmaceutically acceptable derivatives.

As will be appreciated by those skilled in the art, references herein to treatment extend to prophylaxis as well as to the treatment of established infections of symptoms.

The compounds of formula (I) both as the racemic mixture and as the individual enantiomers have been found to inhibit the hepatitis B virus both in vitro and in vivo.

It will be appreciated that the amount of a compound of the invention required for use in treatment will vary not only with the particular compound selected but also with the route of administration, the nature of the condition being treated and the age and condition of the patient and will be ultimately at the discretion of the attendant physician or veterinarian. In general however a suitable dose will be in the range of from about 0.1 to about 750 mg/kg of bodyweight per day preferably in the range of 0.5 to 60 mg/kg/day, most preferably in the range of 1 to 20 mg/kg/day.

The desired dose may conveniently be presented in a single dose or as divided doses administered at appropriate intervals, for example as two, three, four or more sub-doses per day.

The compound is conveniently administered in unit dosage form; for example containing 10 to 1500 mg, conveniently 20 to 1000 mg, most conveniently 50 to 700 mg of active ingredient per unit dosage form.

Ideally the active ingredient should be administered to achieve peak plasma concentrations of the active compound of from about 1 to about 75 µM, preferably about 2 to 50 µM, most preferably about 3 to about 30 µM. 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 orally administered as a bolus containing about 1 to about 100 mg of the active ingredient. Desirable blood levels may be maintained by a continuous infusion to provide about 0.01 to about 5.0 ing/kg/hour or by intermittent infusions containing about 0.4 to about 15 mg/kg of the active ingredient.

While it is possible that, for use in therapy, a compound of the invention may be administered as the raw chemical it is preferable to present the active ingredient as a pharmaceutical formulation.

The invention thus further provides a pharmaceutical formulation comprising a compound of formula (I) or a pharmaceutically acceptable derivative thereof together with one or more pharmaceutically acceptable carriers therefor and, optionally, other therapeutic and/or prophylactic ingredients.., The carrier(s) must be "acceptable" in the sense of being compatible with the other ingredients of the formulation and not deleterious to the recipient thereof.

Pharmaceutical formulations include those suitable for oral, rectal, nasal, topical (including buccal and sub-lingual), vaginal or parenteral (including intramuscular, sub-cutaneous and intravenous) administration or in a form suitable for administration by inhalation or insufflation. The formulations may, where appropriate, be conveniently presented in discrete dosage units and may be prepared by any of the methods well known in the art of pharmacy. All methods include the step of bringing into association the active compound with liquid carriers or finely divided solid carriers or both and then, if necessary, shaping the product into the desired formulation.

Pharmaceutical formulations suitable for oral administration may conveniently be presented as discrete units such as capsules, cachets or tablets each containing a predetermined amount of the active ingredient; as a powder or granules; as a solution, a suspension or as an emulsion. The active ingredient may also be presented as a bolus, electuary or paste. Tablets and capsules for oral administration may contain conventional excipients such as binding agents, fillers, lubricants, disintegrants, or wetting agents. The tablets may be coated according to methods well known in the art. Oral liquid preparations may be in the form of, for example, aqueous or oily suspensions, solutions, emulsions, syrups or elixirs, or may be presented as a dry product for constitution with water or other suitable vehicle before use. Such liquid preparations may contain conventional additives such as suspending agents, emulsifying agents, non-aqueous vehicles (which may include edible oils), or preservatives.

The compounds according to the invention may also be formulated for parenteral administration (e.g. by injection, for example bolus injection or continuous infusion) and may be presented in unit dose form in ampoules, pre-filled syringes, small volume infusion or in multi-dose containers with an added preservative. The compositions may take such forms as suspensions, solutions, or emulsions in oily or aqueous vehicles, and may contain formulatory agents such as suspending, stabilizing and/or dispersing agents. Alternatively, the active ingredient may be in powder form, obtained by aseptic isolation of sterile solid or by lyophilization from solution, for constitution with a suitable vehicle, e.g. sterile, pyrogen-free water, before use.

For topical administration to the epidermis the compounds according to the invention may be formulated as ointments, creams or lotions, or as a transdermal patch. Ointments and creams may, for example, be formulated with an aqueous or oily base with the addition of suitable thickening and/or galling agents. Lotions may be formulated with an aqueous or oily base and will in general also contain one or more emulsifying agents, stabilizing agents, dispersing agents, suspending agents, thickening agents, or coloring agents.

Formulations suitable for topical administration in the mouth include lozenges comprising active ingredient in a flavored base, usually sucrose and acacia or gum tragacanth; pastilles comprising the active ingredient in an inert base such as gelatin and glycerin or sucrose and acacia; and mouthwashes comprising the active ingredient in a suitable liquid carrier.

Pharmaceutical formulations suitable for rectal administration wherein the carrier is a solid are most preferably presented as unit dose suppositories. Suitable carriers include cocoa butter and other materials commonly used in the art, and the suppositories may be conveniently formed by admixture of the active compound with the softened or melted carrier(s) followed by chilling and shaping in moulds.

Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or sprays containing in addition to the active ingredient such carriers as are known in the art to be appropriate.

For intra-nasal administration the compounds of the invention may be used as a liquid spray or dispersible powder or in the form of drops.

Drops may be formulated with an aqueous or non-aqueous base also comprising one or more dispersing agents, solubilizing agents or suspending agents. Liquid sprays are conveniently delivered from pressurized packs.

For administration by inhalation the compounds according to the invention are conveniently delivered from an insufflator, nebulizer or a pressurized pack or other convenient means of delivering an aerosol spray. Pressurized packs may comprise a suitable propellant such as dichlorodifluoromethane, trichlorofluoromethane, dichlorotetrafluoroethane, carbon dioxide, nitrogen or other suitable gas. In the case of a pressurized aerosol the dosage unit may be determined by providing a valve to deliver a metered amount.

Alternatively, for administration by inhalation or insufflation, the compounds according to the invention may take the form of a dry powder composition, for example a powder mix of the compound and a suitable powder base such as lactose or starch. The powder composition may be presented in unit dosage form in, for example, capsules or cartridges or e.g. gelatin or blister packs from which the powder may be administered with the aid of an inhalator or insufflator.

When desired the above described formulations adapted to give sustained release of the active ingredient may be employed.

The pharmaceutical compositions according to the invention may also contain other active ingredients such as antimicrobial agents, or preservatives.

The compounds of the invention may also be used in combination with other therapeutic agents for example other antiinfective agents. In particular the compounds of the invention may be employed together with known antiviral, antibacterial, antifungal or immunomodulating agents.

The invention thus provides, in a further aspect, a combination comprising a compound of formula (I) or a physiologically acceptable derivative thereof together with another therapeutically active agent, in particular an antiviral, antibacterial, antifungal or immunomodulating agents.

The combinations referred to above may conveniently be presented for use in the form of a pharmaceutical formulation and thus pharmaceutical formulations comprising a combination as defined above together with a pharmaceutically acceptable carrier therefor comprise a further aspect of the invention.

The individual components of such combinations may be administered either sequentially or simultaneously in separate or combined pharmaceutical formulations.

When a compound of formula (I) or a pharmaceutically acceptable derivative thereof is used in combination with a second therapeutic agent active against the same virus the dose of each compound may be either the same as or differ from that when the compound is used alone. Appropriate doses will be readily appreciated by those skilled in the art.

The invention is illustrated by the following examples which should not be interpreted as a limitation of the invention.

Example 1 cis- and trans-2-benzoyloxymethyl-5-(N ₄ '-acetyl-5'-fluoro-cytosin-1'-yl)-1,3-oxathiolane

5-Fluorocytosine (4.30 g, 33.3 mmol), hexamethyldisilazane (25 ml) and ammonium sulfate (120 mg) were boiled under reflux until the cytosine dissolved (3 hours) and then further refluxed for z hours. The hexamethyldisilazane is evaporated in vacuo and toluene (100 nl) was added to the residue to co-evaporate the solvents. The resulting solution, bis(trimethylsilyl)-fluoro-cytosine in dichloromethane (40 ml) was added under argon to a solution of 2-benzoyloxymethyl-5-acetoxy-1,3-oxathiolane (8.537 g, 30.3 mmol) in dry dichloromethane (100 ml) and molecular sieves (4A, 2 g) previously prepared under argon and cooled at 0°C for 20 minutes. [(Trifluoromethane-sulfonyl)oxy]trimethylsilane (6 ml, 31 mmol) was added to this mixture at 0°C and the resulting solution was stirred at 25°C for approximately 18 hours. The reaction mixture was then treated with 300 ml of saturated solution of sodium bicarbonate and stirred at room temperature for 2 hours. The filtrate was shaken two times with 300 ml of brine and one time with distilled water. The organic layer was dried over magnesium sulfate, filtered and evaporated to dryness. This afforded a crude 5-fluoro-cytosine derivative (10.1 g). R_f:0.57 (EtOAc:MeOH 9:1).

This residue was acetylated in the next step without further purification. The crude material was dissolved in dry dichloromethane (120 ml) in a 500 ml round bottom flask under argon. Triethylamine (12.7 ml, 91.9 mmol) and dimethyl aminopyridine (111 mg, 0.9 mmol) were added to the solution. The flask was then immersed in an ice bath for 1 hour under argon. Acetic anhydride (4.3 ml, 45 mmol), distilled over sodium acetate, was syringed into the cooled flask. The mixture was stirred overnight and then carefully decanted into an erlenmeyer flask containing saturated sodium bicarbonate solution. The product was then washed with distilled water followed by brine solution. The methylene chloride portions were dried and evaporated under high vacuum to dryness, yielding an acetylated α/β mixture as a colorless foam, weighing 9.6 g after drying. Flash chromatography of this material using ethylacetate:methanol (9:1) afforded 3.1 g, 7.8 mmol (46%) pure trans-(benzoyloxymethyl-5-(N₄'-acetyl-5'-fluoro-cytosin-1'-yl)-1,3-oxathiolane) and 3.5 g, 8.9 mmol (30%) pure cis-(benzoyloxymethyl-5-(N₄'-acetyl-5'-fluoro-cytosin-1'-yl)-1,3-oxathiolane). trans-isomer: R_f:0.65 in ethyl acetate:methanol 9:1 U.V.: (MeOH) Lambda max: 309 nm ¹H-NMR δ (ppm in CDCl₃) 8.77 (b, 1H; C₄'-NH-Ac) 8.06 (m, 2H; aromatic) 7.70 (d, 1H; C₆'-H, J_6'F=6.3Hz) 7.62 (m, 1H; aromatic) 7.49 (m, 2H; aromatic) 6.51 (dd, 1H; C₅-H) 5.91 (dd, 1H; C₂-H) 4.48 (dd, 2H; C₂-CH ₂OCOC₆H₅) 3.66 (dd, 1H; C₄-H) 3.34 (dd, 1H; C₄-H) 2.56 (s, 3H; NH-COCH ₃) cis-isomer: R_f:0.58 in ethyl acetate:methanol 9:1 U.V.: (MeOH) Lambda max: 309nm ¹H-NMR δ (ppm in CDCl₃) 8.72 (b, 1H; C₄'-NH-AC) 8.06 (m, 2H; aromatic) 7.87 (d, 1H; C₆'-H, J_6F=6.2Hz) 7.60 (m, 1H; aromatic) 7.49 (m, 2H; aromatic) 6.32 (dd, 1H; C₅-H) 5.47 (dd, 1H; C₂-H) 4.73 (dd, 2H; C₂-CH ₂OCOC₆H₅) 3.62 (dd, 1H; C₄-H) 3.19 (dd, 1H; C₄-H) 2.55 (s, 3H; NH-COCH ₃)

Example 2 Cis- and trans-hydroxymethyl-5-(5'-fluorocytosin-1'-yl)-1,3-oxathiolane

1.0 g (2.54 mmol) of trans-2-benzoyloxymethyl-5-(N₄'-acetyl-5'-fluorocytosin-1'-yl)-1,3-oxathiolane was stirred in 25 ml of methanolic ammonia at 0° for 1 hour and then overnight at room temperature. The mixture was evaporated under reduced pressure. The residue as triturated twice (2 x 30 ml) with anhydrous ether. The solid residue was recrystallized in absolute ethanol to give 484 mg (1.95 mmol, 77%) of desired product trans-(hydroxymethyl-5-(5'-fluorocytosin-1'-yl)-1,3-oxathiolane): m.p. 219-221°C; R_f=0.21 in ethyl acetate: methanol (9:1), which was identified by ¹H, ¹³C-NMR and U.V. Lambda max (H₂O) 280.9 nm.

1.2 g (3.05 mmol) of cis-2-benzoyloxymethyl-5-(N₄'-acetyl-5'-fluoro-cytosin-1'-yl)-1,3-oxathiolane was stirred in 30 ml of methanolic ammonia at 0°C for 1 hour and then overnight at room temperature. The mixture was evaporated under reduced pressure. The residue was triturated twice (2 x 30 ml) with anhydrous ether. The solid residue was recrystallized in absolute ethanol to give 655 mg (2.64 mmol, 87%) of pure product cis-(hydroxymethyl-5-(5'-fluorocytosin-1'-yl)-1,3-oxathialane): m.p. 204-206°C; R_f=0.21 in ethylacetate: methanol (9:1). The desired compound was identified by ¹H, ¹³C-NMR and U.V. Lambda max (H₂O) 280.9 nm. trans-isomer: ¹H-NMR δ (ppm in DMSO-d₆): 7.85 (d, 1H; C₆'-H, J_CF=7.01 Hz) 7.83 (d, 2H; C₄'-NH₂) 6.30 (dd, 1H; C₅-H) 5.60 (t, 1H; C₂-H) 5.18 (t, 1H; C₂-CH₂-OH) 3.49 (m, 3H; C₂-CH ₂OH+C₄ H) 3.17 (dd, 1H; C₄-H) ¹³CNMR (DMSO-d₆), (Varian XL 300); δ in ppm

153.47	158.20	134.65	126.24

88.20	36.18 .	87.16	64.71

cis-isomer: ¹H-NMR δ (ppm in DMSO=d₆): 8.22 (d, 1H; C₆'-H, J_CF=7.26 Hz) 7.843 (d, 2H; C₄'-NH ₂) 6.16 (t, 1H; C₅-H) 5.43 (t, 1H; C₂-CH₂-OH) 5.19 (t, 1H; C₂-H) 3.77 (m, 2H; C₂-CH ₂OH) 3.35 (dd, 1H; C₄-H) 3.12 (dd, 1H; C₄-H) ¹³CNMR (DMSO-D₆)

			C6'
153.46	158.14	134.63	126.32

86.82	36.80	86.77	62.32

Example 3 Biological Results

• (A) Newborn ducklings were infected with duck hepatitis B virus (DHBV). After 5 to 7 days post-infection, samples of blood were taken from the ducklings and examined for DHBV DNA using dot hybridization with a specific DNA probe (Mason et al., Proc. Natl. Acad. Sci. USA 79, pp. 3997-4001 (1982)). The livers were removed from dot-blot positive ducklings and used to produce primary hepatocyte cultures infected with DHBV as previously described (Tuttleman et al., J. of Virology, 58, pp. 17-25). After 2 days in culture, antiviral agents were added to the culture media. The media were changed every 2 days and at selected times, the cells were removed and the total DNA extracted.

The DNA was spotted on nitrocellulose paper and probed with the ³²P-labelled DHBV DNA probe in accordance with the following procedure. The DNA from DHBV-infected hepatocytes was extracted and spotted onto a nitrocellulose filter. The above described ³²P-nick translated-DHBV DNA (pDH-010 = DHBV) probe was used. The DNA was extracted from 6-cm cell culture dishes at various times post-plating. In the virus control (VC) group, cells were harvested at 2, 6, 8, 10, 14, 18 and 20 days. Duplicate samples were spotted for days 14, 18 and 20. In drug-treated groups, cells were harvested on days 8, 14 and 20. Drugs were added to the culture at 2 days post-plating and maintained throughout media changes every 2 days. The total intracellular DNA was extracted from cells using the standard phenol extraction method. The cells in a 6-cm diameter Petri dish (approximately 5 x 10⁶ cells) were lysed in a lysis buffer containing 0.2% SDS, 150 mM Tris-HC1 pH 8.0, 10 mM EDTA, 5 mM EGTA, and 150 mM NaCl. The cell lysate was digested with 0.5 mg/ml of pronase E (available from Sigma) at 37°C for 2 hours and proteinized by extraction with an equal volume of phenol saturated with 20 mM Tris-HC1, pH 7.5, 0.5 mM EDTA and 0.1% 8-hydroxyquinoline. Concentrated ammonium acetate (pH 7.0 (2.5 M)) was added to the aqueous phase to yield a 0.25 M ammonium acetate solution and the nucleic acids were precipitated with 2 volumes of 100% ethanol. The pellet of nucleic acid was washed with ethanol and dried. The DNA was dissolved in a solution containing 12.5 mM Tris-HCl, pH 7.5, 10 mM EDTA, 30% glycerol and 0.01% bromophenol blue. One twelfth of the DNA sample was spotted onto the nitrocellulose for dot-blot analysis.

The drugs tested were scored on a scale of 0 (no activity) to ++++ (high activity).

The compounds tested were 1,3 oxathiolanes and two known inhibitors of hepatitis B, 2', 3'-dideoxy-guanosine (ddG) and 2,6-diaminopurine-9--D-2',3'-dideoxyribofuranoside (ddDAPR)-(European Patent publication 0302760A).

The results are shown in Table 1.

	Activity
	+
	+++
	++
	++++
ddG	++++
ddDAPR	++++

Claims (29)

1. Use for the manufacture of a medicament for the treatment of hepatitis B infection of a compound of formula (I) or a pharmaceutically acceptable salt thereof: wherein Z is S, S = O or SO₂; R₁ is hydrogen or an acyl; R₂ is: R₃ is selected from hydrogen, unsubstituted C_1-6 alkyl, and C_1-4-alkyl substituted with a heteroatom; R₄ and R₅ are each independently selected from hydrogen, C_1-6 alkyl, bromine, chlorine, fluorine, and iodine; R₆ is selected from hydrogen, CN, carboxy ethoxycarbonyl, carbamoyl and thiocarbamoyl; and X and Y are independently selected from bromine, chlorine, fluorine, iodine, amino and hydroxy groups; provided that: R₂ is not cytosine or 5-F-cytosine when Z is S.
2. The use according to claim 1, wherein the compound of formula (I) is present in its cis configuration.
3. The use according to claim 2, wherein the compound of formula (I) is present as its (-)-enantiomer.
4. The use according to claim 2, wherein the compound of formula (I) is present at its (+)-enantiomer.
5. The use according to claim 2, wherein the compound of formula (I) is present as a racemic mixture.
6. The use according to any one of claims 1-5, wherein Z is S.
7. The use according to any one of claims 1-6, wherein R₁ is H.
8. The use according to any one of claims 1-7, wherein R₂ is
9. The use according to any one of claims 1-7, wherein R₂ is:
10. The use according to any one of claims 1-9, wherein said medicament is administered at a dose of about 0.1 to 750 mg/kg of bodyweight per day.
11. The use according to any one of claims 1-10, wherein said medicament is adapted for oral, parenteral, rectal, nasal, vaginal, or topical administration.
12. The use according 10 any one of claims 1-11, wherein said medicament is present in dosage unit form.
13. The use according to any one of claims 1-12, wherein the composition contains 10 to 1500 mg of the compound of formula (I).
14. The use according to any one of claims 1-13, wherein said medicament is administered with a pharmaceutically acceptable carrier.
15. The use according to any one of claims 1 to 14, wherein the compound is adininistered in combination with a therapeutically active agent selected from antiviral, antibacterial, antifungal aod immunomodulating agents.
16. The use for the manufacture of a medicament for the treatment of hepatitis B infection of a compound selected from:

    cis-2-benzoyloxymethyl-5-(cytosin-1'-yl)-1,3-oxathiolane in the fom of a racemic mixture or a single enantiomer, trans-2-benzoyloxymethyl-5-(cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, and mixtures thereof;

    cis-2-hydroxymethyl-5-(N₄'-acetyl-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, trans-2-hydroxymethyl-5-(N₄'-acetyl-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, and mixtures thereof;

    cis-2-benzyloylmethyl-5-(N₄'-acetyl-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, trans-2-benzyloylmethyl-5-(N₄'-acetyl-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, and mixtures thereof;

    cis-2-benzyloylmethyl-5-(N₄'-acetyl-5-fluoro-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, trans-2-benzyloylmethyl-5-(N₄'-acetyl-5-fluoro-cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer, and mixtures thereof;

    cis-2-hydroxymethyl-5-(cytosin-1'-yl)-3-oxo-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer;

    cis-2-hydroxymethyl-5-(thymin-N-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer;

    cis-2-hydroxymethyl-5-(N,N-dimethylaminomethylene cytosin-1'-yl)-1,3-oxathiolane in the form of a racemic mixture or a single enantiomer; and

    pharmaceutically acceptable salts thereof.
17. The use according to claim 16, wherein the compound is present as its (-)-enantiomer.
18. The use according to claim 16, wherein the compound is present as its (+)-enantiomer.
19. the use according to claim 16, wherein the compound is present as a racemic mixture.
20. The use according to claim 16, wherein the compound is cis-2-hydroxymethyl-5-(N,N-dimethylaminomethylene-cytosin-1'-yl)-1,3-oxathiolane, or a pharmaceutically acceptable salt thereof.
21. The use according to claim 20, wherein the compound is present as a racemic mixture.
22. The use according to claim 20, wherein the compound is present as its (-)-enantiomer.
23. The use according to claim 20, wherein the compound is present as its (+)-enantiomer.
24. Use for the manufacture of a medicament for the treatment of hepatitis B infections of:

    a compound selected from

    1) cis-2-hydroxymethyl-5-(5'-fluorocytosin-1'-yl)-1,3-oxathiolane or a pharmaceutically acceptable salt thereof, in the form of a racemic mixture or a single enantiomer,

    2) trans-2-hydroxymethyl-5-(5'-fluorocytosin-1'-yl)-1,3-oxathiolane or a pharmaceutically acceptable salt thereof, in the form of a racemic mixture or a single enantiomer, and

    3) mixtures thereof;

    at least one other therapeutically active antiviral agent; and

    optionally, a pharmaceutically acceptable carrier.
25. The use according to claim 24, wherein the compound is present as a racemic mixture.
26. The use according to claim 24, wherein the compound is present as a single enantiomer.
27. The use according to claim 24, wherein the compound is present as its (-)-enantiomer.
28. The use according to claim 24, wherein the compound is present at its (+)-enantiomer.
29. The use according to any one of claims 16 to 28, wherein the medicament contains 10 to 1500 mg of said compound.