WO2008007153A2 - Antiviral compounds - Google Patents

Abstract

There are described compounds of formula (I): wherein, at least one of R1, R2 and R3 represents a group S-L- and the remainder represent H; S represents a binding group; L represents a linker chain; X represents O or NH; and pharmaceutically acceptable derivatives thereof, methods for their preparation, compositions containing them and their use as antiviral agents.

Description

Antiviral Compounds

This invention relates to novel compounds, processes for their preparation, pharmaceutical compositions containing them and methods of treatment involving their use.

Ribavirin(l-, β-D-ribofuranosyl-l,2,4-triazole-3-carboxamide) is a nucleoside analogue that has demonstrated efficacy in treating viral diseases both as monotherapy (respiratory syncytial virus, Hall, C. B. ; McBride, J. T. ; Walsh, E. E. ; Bell, D. M. ; Gala, C. L. ; Hildreth, S. ; Ten Eyck, L. G. ; W. J. Hall. Aerosolized ribavirin treatment of infants with respiratory syncytial viral infection. N. Engl. J. Med. 1983, 308, 1443- 1447), and in combination therapy with interferon-alpha (hepatitis C virus, Reichard, O.; Norkrans, G.; Fryden, A.; Braconier, J H.; Sonnerborg, A.; Weiland, O: Randomized, double blind, placebo controlled trial of interferon alpha2B with and without ribavirin for chronic hepatitis C, Lancet 1998, 351, 8387). Combinations of ribavirin with pegylated interferon cc2a and with pegylated interferon cc2b have also been reported.

Recently reported studies indicate that the in vivo utility of ribavirin can result not only from direct inhibition of viral replication, but also from its ability to enhance T cell- mediated immunity (Hultgren, C; Milich, D.R.; Weiland, O.; Sallberg, M. The antiviral compound ribavirin modulates the T helper Typel/Type2 subset balance in hepatitis B and C virusspecific immune responses, J. Gen. Virol. 1998, 79, 2381-2391 ; Ning, Q. ; Brown, D. ; Parodo, J. ; Cattral, M. ; Fung, L. ; Gorczynski, R. ; Cole, E., Fung, L.; Ding, J. W. ; Liu, M. F.; Rotstein,O. ; Phillips, M. J.; Levy, G. Ribavirin inhibits viral- induced macrophage production of tumor necrosis factor, interleukin-1, procoagulant activity fgl2 prothrombinase and preserves ThI cytokine production but inhibits Th2 cytokine response. J. Immunol. 1998, 160, 3487-3493; Martin, M. J. ; Navas, S.; Quiroga, J. A. ; Pardo, M.; Carreno, V. Effects of the ribavirin interferon alpha combination on cultured peripheral blood mononuclear cells from chronic hepatitis C patients.; Cytokine 1998, 79, 2381-2391). This immunomodulatory effect of ribavirin is demonstrable in vitro by measuring the levels of Type 1 cytokines produced by activated T cells from both humans and mice (Tarn, R. C.Pai, B.; Bard, J.; Lim, C; Averett, D. R.; Phan, U. T. ; Milovanovic, T. Ribavirin polarizes human T cell responses towards a Type 1 cytokine profile; J. Hepatol. 1999, 30, 376-382), and by other measures. The induction of a Type 1 cytokine bias by ribavirin is functionally significant in vivo in murine systems (Tarn, R. C. ; Lim, C; Bard, J.; Pai, B.: Contact hypersensitivity responses following ribavirin treatment in vivo are influenced by Type 1 cytokine polarization, regulation of ILlO expression and co-stimulatory signaling. J. Immunol. 1999, 163, 3709-3717).

Mammalian immune systems contain two major classes of lymphocytes: B lymphocytes (B cells), which originate in the bone marrow; and T lymphocytes (T cells) that originate in the thymus. B cells are largely responsible for humoral immunity (i.e. antibody production), while T cells are largely responsible for cell-mediated immunity.

T cells are generally considered to fall into two subclasses, helper T cells and cytotoxic T cells. Helper T cells activate other lymphocytes, including B cells and cytotoxic T cells, and macrophages, by releasing soluble protein mediators called cytokines that are involved in cell-mediated immunity. As used herein, lymphokines are a subset of cytokines.

Helper T cells are also generally considered to fall into two subclasses, Type 1 and Type 2. Type 1 cells produce interleukin 2 (IL-2), tumor necrosis factor (TNFa) and interferon gamma (IFNγ), and are responsible primarily for cell-mediated immunity such as delayed type hypersensitivity and antiviral immunity. In contrast, Type 2 cells produce interleukins, IL4, IL-5, IL-6, IL-9, IL-10 and IL-13, and are primarily involved in assisting humoral immune responses such as those seen in response to allergens, e. g. IgE andIgG4 antibody isotype switching (Mosmann, 1989,Annu Rev Immunol, 7: 145- 173).

As used herein, the terms Type 1 and Type 2 "responses" are meant to include the entire range of effects resulting from induction of Type 1 and Type 2 lymphocytes, respectively. Among other things, such responses include variation in production of the corresponding cytokines through transcription, translation, secretion and possibly other mechanisms, increased proliferation of the corresponding lymphocytes, and other effects associated with increased production of cytokines, including motility effects.

According to the invention there are provided compounds of formula (I),

wherein, at least one of R¹, R² and R³ represents a group S-L- and the remainder represent H, S represents a binding group, L represents a linker chain, X represents O or NH, and pharmaceutically acceptable derivatives thereof.

The present invention will now be described with reference to the following drawings, in which:

Fig. 1 shows an NMR spectrum of compound 1; Fig. 2 shows an NMR spectrum of compound 2;

Fig. 3 shows an NMR spectrum of compound 3;

Fig. 4 shows an NMR spectrum of compound 4;

Fig. 5 shows plasma concentrations of certain compounds according to the invention;

Fig. 6 shows red blood cell (RBC) concentrations of certain compounds according to the invention.

SL represents one of the following groups:

(II) (III) Wherein in formula (II), either: one of A and A' represents L and the other represents H, or A is L and -D-A' represents -OH, -OAcyl or -NHAcyl, or A represents H and D represents NH and A' = L, and in each case R⁴ = Acyl or H and L is as defined above.

Preferably, group S represents an oligosaccharide terminating in a galactosamine or galactose residue. Suitable sugars that S may represent include galactosamine, galactose or lactose.

L may be linked at any of the hydroxy substituents on the ribavirin moiety (Ia), i.e. the 2- , 3- or 5- OH groups, to give O-L-S. Alternatively, L may be linked to the ribavirin moiety (Ia), represented by the following structure,

(Ia)

by substituting any one of the 2-, 3- or 5- OH substituents, e.g. by NH-L-S. Preferably, group X represents O when either or both of R² and R³ represent S-L-, and X represents O or NH when R¹ represents S-L-.

Preferably, L includes COCH₂-, CO- or benzylene which is linked to -O- or -X- of the ribavirin moiety (Ia).

Preferably, R¹ represents L and R² and R³ both represent H, or

X represents O, R¹ represents H, R² represents L and R³ represents H, or X represents O and R¹ represents H, R² represents H and R³ = L, or X represents O and R¹ represents H, R² represents L and R³ represents L.

L may be further substituted by S', where S' has the same definition as S defined above. Preferably, S binds to an asialoglycoprotein receptor.

Preferably, L represents one of the following groups:

(IV) wherein, n is an integer from 0 to 6 inclusive;

Y represents O; -OCH₂-; -(CR⁶R⁷)d-, where R⁶ and R⁷ independently represent H or alkyl; cycloalkylene; arylene; or single bond; and d represents an integer from 0 to 6 inclusive;

or

(V) wherein, p and z independently represent 1 or 2; s represents an integer from 1 to 4; b, c, r and t independently integers from 0 to 3 inclusive;

Q and Q' independently represent -(CR⁶R⁷)_qCONH-, where R⁶ and R⁷ are as defined above, and q is 1 or 2; or a single bond;

T is CH or N; U is a single bond, -CONH- or -CO-; or

(VI) wherein,

E represents -(CR⁶R⁷)_q-, where R⁶ and R⁷ are as defined above, q is as defined above; or benzylene;

Z represents a single bond, -CO-, -NHCO(CH₂)_r-, wherein r is as defined above;

or

(VII)

w represents 0 or 1 ; q is as defined above; U' represents -CO- or -CONH-;

Z' represents -ONHCO-CH₂-

or H; and

S is as defined above.

Although it is not necessary for the functioning of the invention, we prefer that L is cleavably connected to the ribavirin moiety (Ia), such that in vivo, particularly in hepatocytes, the compound of formula (I) releases ribavirin or an antiviral derivative thereof. Where L is linked to a ribavirin 5 -hydroxy substituent, it is preferably cleavably linked. However, linkages at the 2- or 3- hydroxyl position may be metabolically stable, as the compounds of formula (I) may be active as such.

According to the invention we also provide a process for the production of a compound of formula (I), or a pharmaceutically acceptable derivative thereof, which comprises a) reacting a compound of formula (VIII),

Si-L-Zi (VIII) in which Zi represents a leaving group,

Si is a group S as defined above or a protected S, and L is as defined above, with a compound of Formula (IX),

Ra (IX)

in which R_a is a ribavirin or protected ribavirin, or b) reacting a compound of Formula (X),

Z₂-L-R_a (X)

in which Z₂ is a leaving group and L and R_a are as defined above, with a compound of Formula (XI),

Sa (XI)

in which S_a is a group S as defined above, or a protected derivative thereof, and where desired or necessary, converting the resulting compound into a compound of formula (I) by removing protecting groups.

Reactions (a) and (b) may be carried out using conventional conditions well known to the person skilled in the art of synthetic organic chemistry. Conditions are described, for example, in standard text books of practical organic chemistry, e.g. Fieser, Organic Syntheses, and the like.

Specific compounds of formula (I) may be synthesised as follows:

Scheme 1:

Compound 1

Figure 1 shows an NMR spectrum of compound 1.

Scheme 2:

Compound 2

Figure 2 shows an NMR spectrum of compound 2. Scheme 3:

Compound 3 Figure 3 shows an NMR spectrum of compound 3.

Scheme 4:

Compound 4 Figure 4 shows an NMR spectrum of compound 4.

Scheme 5:

Reaction conditions: i MeOH, acetone, 2,2-dimethoxy propane, HCl_(g) ii NaH, THF, 70°C then alkyl iodide, 0°C iii 70% aqueous AcOH, 90°C then acetic anhydride, pyridine iv Triazole, DBU, TMSOTf, MeCN v Pd/C, MeOH, hydrogen

Compound 5

Reaction conditions: i DCM, HBr/AcOH, 0°C then benzyl glycolate, DCM, AgOTf, 0°C to RT ii Pd/C, EtOH, hydrogen iii PFP, DCC, DCM, DMAP then NH₂CH₂CH₂NHZ, DMF, NEt₃ iv Pd/C, EtOH, hydrogen v PFP, DCC, DCM, DMAP, Ribavirin derivative vi 7N NH₃, MeOH

Scheme 6:

Reaction conditions: i Diol protection ii Pyridine, MsCl, DMAP iii NaN₃, DMF, 60°C iv 30% aqueous TFA v TES-Cl, pyridine vi Pd/C, EtOH, hydrogen

Reaction conditions: i DCM, HBr/AcOH, 0°C then benzyl glycolate, DCM, AgOTf, 0°C to RT ii Pd/C, EtOH, hydrogen iii PFP, DCC, DCM, DMAP, Ribavirin derivative, DMF, NEt₃ iv TFA, THF, MeOH v 7N NH₃, MeOH

Scheme 7:

Reaction conditions: i MeOH, acetone, 2,2-dimethoxy propane, HCl^g) ii NaH, THF, 70°C then alkyl iodide, 0°C iii 70% aqueous AcOH, 90°C then acetic anhydride, pyridine iv Triazole, DBU, TMSOTf, MeCN v Pd/C, MeOH, hydrogen

Reaction conditions: i BoC₂O, K₂CO₃, aq. Dioxane ii DCM, MsCl, NEt₃, 0°C iii DMF, NaN₃, 85°C iv Pd/C, EtOH, hydrogen

Reaction conditions: i DCM, HBr/AcOH, 0°C then benzyl glycolate, DCM, AgOTf, 0°C to RT ii Pd/C, EtOH, hydrogen iii PFP, DCC, DCM, DMAP, then amine, DMF, NEt₃ iv Pd/C, EtOH, hydrogen v PFP, DCC, DCM, DMAP, Ribavirin derivative vi 7N NH₃, MeOH

Scheme 8:

Reaction conditions: i MeOH, acetone, 2,2-dimethoxy propane, HCl^g) ii NaH, THF, 70°C then alkyl iodide, 0°C iii 70% aqueous AcOH, 90°C then acetic anhydride, pyridine iv Triazole, DBU, TMSOTf, MeCN v Pd/C, MeOH, hydrogen

Reaction conditions: i BoC₂O, K₂CO₃, aq. Dioxane ii Amination of alcohol

Compound 8

Reaction conditions: i DCM, HBr/AcOH, 0°C then benzyl glycolate, DCM, AgOTf, 0°C to RT ii Pd/C, EtOH, hydrogen iii PFP, DCC, DCM, DMAP, then amine, DMF, NEt₃ iv Pd/C, EtOH, hydrogen v PFP, DCC, DCM, DMAP, Ribavirin derivative. vi 7N NH₃, MeOH

Scheme 9:

Reaction conditions: i MeOH, acetone, 2,2-dimethoxy propane, HCl^g) ii NaH, THF, 70°C then alkyl iodide, 0°C iii 70% aqueous AcOH, 90°C then acetic anhydride, pyridine iv Triazole, DBU, TMSOTf, MeCN v Pd/C, MeOH, hydrogen

Reaction conditions: i BoC₂O, NaOH, dioxane, water ii DCC, DMAP, DCM, H₂N(CH₂) ₂NHZ iii HCl, MeOH, THF

Compound 9 Reaction conditions: i DCM, HBr/AcOH, 0°C then benzyl glycolate, DCM, AgOTf, 0°C to RT ii Pd/C, EtOH, hydrogen iii PFP, DCC, DCM, DMAP, then amine, DMF, NEt₃ iv Pd/C, EtOH, hydrogen v PFP, DCC, DCM, DMAP, Ribavirin derivative vi 7N NH₃, MeOH Scheme 10:

Reaction conditions: i MeOH, acetone, 2,2-dimethoxy propane, HCl^g) ii NaH, THF, 70°C then alkyl iodide, 0°C iii 70% aqueous AcOH, 90°C then acetic anhydride, pyridine iv Triazole, DBU, TMSOTf, MeCN v Pd/C, MeOH, hydrogen

Reaction conditions: i TBTU, DMF, NEt₃ ii HCl, MeOH, THF

Compound 10

Reaction conditions: i DCM, HBr/AcOH, 0°C then benzyl glycolate, DCM, AgOTf, 0°C to RT ii Pd/C, EtOH, hydrogen iii PFP, DCC, DCM, DMAP then amine, DMF, NEt₃ iv Pd/C, EtOH, hydrogen v PFP, DCC, DCM, DMAP, Ribavirin derivative vi 7N NH₃, MeOH

Scheme 11:

Reaction conditions: i MeOH, acetone, 2,2-dimethoxy propane, HCl^g) ii NaH, THF, 70°C then alkyl iodide, 0°C iii 70% aqueous AcOH, 90°C then acetic anhydride, pyridine iv Triazole, DBU, TMSOTf, MeCN v Pd/C, MeOH, hydrogen

Reaction conditions: i Boc₂O, CHCl₃, 0°C ii Acrylonitrile, AcOH iii Hydrogen, Raney-Ni, 1.4N NaOH, EtOH

Compound 11

Reaction conditions: i DCM, HBr/AcOH, 0°C then benzyl glycolate, DCM, AgOTf, 0°C to RT ii Pd/C, EtOH, hydrogen iii PFP, DCC, DCM, DMAP then amine, DMF, NEt₃ iv 5% TFA, DCM v PFP, DCC, DCM, DMAP, Ribavirin derivative vi 7N NH₃, MeOH

Scheme 12:

Reaction conditions: i DCM, HBr/AcOH, 0°C then HOCH₂COOMe , DCM, AgOTf, 0°C to RT ii Na, MeOH, CHCl₃ then DOWEX (H+) iii CSA, PhCH(OMe)₂, DMF 60°C, 260mBar

Reaction conditions: i HC(OMe)₃,PPTS, THF ii CDI, NEt₃, DMF then ZNH(CH₂)₂NH₂ iii Pd/C, MeOH, hydrogen iv MeOH, 80°C v 2% TFA in MeOH

Scheme 13:

Reaction conditions: i MeOH, acetone, 2,2-dimethoxy propane, HCl^g) ii NaH, THF, 70°C then alkyl iodide, 0°C iii 70% aqueous AcOH, 90°C then acetic anhydride, pyridine iv Triazole, DBU, TMSOTf, MeCN v Pd/C, MeOH, hydrogen

Reaction conditions: i Ac₂O, iodine ii HBr/AcOH iii Benzyl glycolate, AgOTf, 0°C to RT iv Pd/C, EtOH, hydrogen v PFP, DCC, DCM, then H₂NCH₂CH₂NHZ, Et₃N, DMF vi Pd/C, EtOH, hydrogen vii Ribavirin derivative, PFP, DCC, DCM, then amine, Et₃N, DMF viii 7N NH₃, MeOH

Scheme 14:

Reaction conditions: i MeOH, acetone, 2,2-dimethoxy propane, HCl^g) ii NaH, THF, 70°C then alkyl iodide, 0°C iii 70% aqueous AcOH, 90°C then acetic anhydride, pyridine iv Triazole, DBU, TMSOTf, MeCN v Pd/C, MeOH, hydrogen

Compound 14 Reaction conditions: (R = Z, Fmoc, Boc): i a) HATU, DIPEA, DMF, b) Ac₂O, pyridine ii R=Z: Pd/C, hydrogen, TFA (1 eqv), EtOH ; R=Fmoc: piperidne; R=Boc: TFA/DCM, 1/1, v/v iii Ribavirin derivative, PFP, DCC, DCM, then amine, NEt₃, DMF iv 7N NH₃, MeOH Scheme 15:

Reaction conditions: i DCM, HBr/AcOH, 0°C then HOCH₂COOMe , DCM, AgOTf, 0°C to RT ii Na, MeOH, CHCl₃ then DOWEX (H⁺) iii CSA, PhCH(OMe)₂, DMF 60°C, 260mBar iv NaOH (leq), MeOH:H₂O (v:v 3:1) then IM HCl (0.95 eq).

Reaction conditions: i HC(OMe)₃, PPTS, THF ii ECDI, DCM, DMAP iii Pd/C, EtOH, hydrogen, TFA iv HATU, DIPEA, DMF 4% TFA, MeOH/H₂O

Scheme 16:

Reaction conditions: i DCM, HBr/AcOH, 0°C then HOCH₂COOMe , DCM, AgOTf, 0°C to RT ii Na, MeOH, CHCl₃ then DOWEX (H⁺) iii CSA, PhCH(OMe)₂, DMF 60°C, 260mBar iv NaOH (leq), MeOH:H₂O (v:v 3:1) then IM HCl (0.95 eq).

Compound 16

Reaction conditions: i HC(OMe)₃, PPTS, THF ii ECDI, DCM, DMAP iii Pd/C, EtOH, hydrogen, TFA iv HATU, DIPEA, DMF v 4% TFA, MeOH/H₂O

Scheme 17:

Reaction conditions: i DCM, HBr/AcOH, 0°C then HOCH₂COOMe , DCM, AgOTf, 0°C to RT ii Na, MeOH, CHCl₃ then DOWEX (H+) iii CSA, PhCH(OMe)₂, DMF 60°C, 260mBar iv NaOH (leq), MeOH:H₂O (v:v 3:1) then IM HCl (0.95 eq).

Compound 17

Reaction conditions: i HC(OMe)₃, PPTS, THF ii ECDI₅ DCM, DMAP iii 4% TFA, MeOH/H₂O

Scheme 18:

Reaction conditions: i TIPS-Cl, imidazole, DMF ii Ag₂O, TBAI, DCM, 4-nitrobenzyl bromide iii Pd/C, EtOH/DCM, hydrogen

Compound 18 Reaction conditions: i DCM, HBr/AcOH, 0°C then benzyl glycolate, DCM, AgOTf, 0°C to RT ii Pd/C, EtOH, hydrogen iii HATU, DIPEA, DMF, Ribavirin derivative iv TBAF, THF, DIPEA, DMF v NH₃, MeOH

Scheme 19:

Reaction conditions: i TIPS-Cl, imidazole, DMF ii Ag₂O, TBAI, DCM, 4-nitrobenzyl bromide iii Pd/C, EtOH/DCM, hydrogen

Compound 19

Reaction conditions: i DCM, HBr/AcOH, 0°C then benzyl glycolate, DCM, AgOTf, 0°C to RT ii Pd/C, EtOH, hydrogen iii HATU, DIPEA, DMF, Ribavirin derivative iv TBAF, THF, DIPEA, DMF v NH₃, MeOH

Scheme 20:

Compound 20 Scheme 21:

Compound 21

Scheme 22:

Compound 22 Scheme 23:

Compound 23

Scheme 24:

Compound 24

Scheme 25:

Compound 25

Scheme 26:

Compound 26

Scheme 27:

Scheme 28:

Compound 28

Scheme 29:

Compound 29

Scheme 30:

Compound 30

Scheme 31 :

Compound 31

Scheme 32:

Compound 32

In the above processes it may be necessary for any functional groups, e.g. hydroxy or amino groups, present in the starting materials to be protected. Suitable protecting groups and methods for their removal are, for example, those described in "Protective Groups in Organic Synthesis" by T.W. Greene and P.G.M. Wuts, John Wiley and Sons Inc., 1991.

Hydroxy groups may, for example, be protected by arylmethyl groups such as phenylmethyl, diphenylmethyl or triphenylmethyl, or as tetrahydropyranyl derivatives.

When S, L or the ribavirin moity includes an amino protecting group, suitable amino protecting groups include arylmethyl groups such as benzyl, (R,S)-a-phenylethyl, diphenylmethyl or triphenylmethyl, and acyl groups such as acetyl, trichloroacetyl or trifluoroacetyl. Conventional methods of deprotection may be used.

Arylmethyl groups may, for example, be removed by hydrogeno lysis in the presence of a metal catalyst e.g. palladium on charcoal. Tetrahydropyranyl groups may be cleaved by hydrolysis under acidic conditions. Acyl groups may be removed by hydrolysis with a base such as sodium hydroxide or potassium carbonate, or a group such as trichloroacetyl may be removed by reduction with, for example, zinc and acetic acid.

Other compounds of formula (I) may be made from commercially available starting materials using analogous processes. Pharmaceutically acceptable derivatives of the compound of formula (I) include pharmaceutically acceptable salts, esters and amides thereof.

Suitable pharmaceutically acceptable salts of the compounds of formula (I) include acid addition salts derived from inorganic and organic acids, such as hydrochlorides, hydrobromides, hydroiodides, sulphates, phosphates, maleates, tartrates, citrates, benzoates, 4-methoxybenzoates, 2- or 4-hydroxybenzoates, 4-chlorobenzoates, benzenesulphonates, p-toluenesulphonates, naphthalenesulphonates, methanesulphonates, sulphamates, ascorbates, salicylates, acetates, diphenylacetates, triphenylacetates, adipates, fumarates, succinates, lactates, glutarates, gluconates, hydroxy-naphthalenecarboxylates, e.g. 1 -hydroxy or 3-hydroxy-2- naphthalenecarboxylates, or oleates.

The compounds may also form salts with suitable bases. Examples of such salts include alkali metal, e.g. sodium and potassium, and alkaline earth metal, e.g. calcium and magnesium, and ammonium, salts.

The compound of formula (I) may be obtained in the form of a salt, conveniently a pharmaceutically acceptable salt. Where desired, such salts may be converted to the free bases using conventional methods. Pharmaceutically acceptable salts may be prepared by reacting the compound of formula (I) with an appropriate acid or base in the presence of a suitable solvent.

Suitable pharmaceutically acceptable esters of the compounds of formula (I) include alkyl C_1-4 esters, e.g. ethyl ester. The esters may be made by conventional techniques, e.g. esterification or transesterification.

Suitable amides include unsubstituted or mono- or di-substituted alkyl C_1-4 or phenyl amides, and may be made by conventional techniques, e.g. reaction of an ester of the corresponding acid with ammonia or an appropriate amine. The compounds of formula (I) may exhibit tautomerism, they may also contain one or more asymmetric carbon atoms and may therefore exhibit optical and/or diastereoisomerism. Diastereoisomers may be separated using conventional techniques, e.g. chromatography or fractional crystallisation. The various optical isomers may be isolated by separation of a racemic or other mixture of the compounds using conventional, e.g. fractional crystallisation or HPLC, techniques. Alternatively the desired optical isomers may be made by reaction of the appropriate optically active starting materials under conditions which will not cause racemisation.

By the term MW we mean microwave radiation.

By the term alkyl we mean straight, branched or cyclic saturated or unsaturated alkyl groups. Preferably alkyl is C_1-6, more preferably C_1-4, for example methyl. Cycloalkylene includes C₃-C₈ cycloalkylene, including cyclohexylene and preferably includes the following group:

Arylene includes phenylene and preferably includes the following group:

We prefer compounds of formula (I) in which R¹ represents S-L-. We further prefer compounds of formula (I) in which X represents O.

Suitable sugars that may be mentioned include galactosamine, galactose and lactose. The sugar may be cleavably linked to -L- by any residue which may be cleaved in vivo, to release the parent sugar. The sugar may linked to -L- by an oxygen or a nitrogen; for example the sugar may be a 6-galactosyl residue or a 5- galactosamine residue.

Specific examples of L include:

wherein r, n and S are as defined above.

When R⁴ represents acyl, acyl includes alkanoyl C₁-C₆, preferably acetyl. We particularly prefer combinations of S-L that are likely to bind and to be cleaved by asialoglycoprotein within hepatocytes, to release ribavirin.

Most preferably, compounds of formula (I) include: Compound 1

Compound 2

Compound 3

Compound 4

Preferably, compounds of formula (I) additionally include: Compound 5

Compound 6

Compound 7

Compound 8

Compound 9

Compound 10

Compound 11

Compound 12

Compound 13

Compound 14

Compound 15

Compound 16

Compound 17

Compound 18

Compound 19

Compound 20

Compound 21

Compound 22

Compound 23

Compound 24

Compound 25

Compound 26

Compound 27

Compound 28

Compound 29

Compound 30

Compound 31

Compound 32

The compounds of formula (I) are useful in that they exhibit pharmacological activity in animals. In particular the compounds are prodrugs of ribavirin. The compounds of the invention may be used to treat an infection, an infestation, a cancer or tumor or an autoimmune disease. It is further contemplated that the compounds of the invention may be used to target conditions or diseases in specific organs of a patient, such as the liver or heart.

Infections contemplated to be treated with the compounds of the present invention include respiratory syncytial virus (RSV), hepatitis B virus (HBV), hepatitis C virus (HCV), herpes simplex type 1 and 2, herpes genitalis, herpes keratitis, herpes encephalitis, herpes zoster, human immunodeficiency virus (HIV), influenza A virus, hantann virus (hemorrhagic fever), human papilloma virus (HPV), measles, and fungus.

Infestations contemplated to be treated with the compounds of the present invention include protozoan infestations, as well as helminth and other parasitic infestations.

Cancers or tumors contemplated to be treated include those caused by a virus, and the effect may involve inhibiting the transformation of virus-infected cells to a neoplastic state, inhibiting the spread of viruses from transformed cells to other normal cells and/or arresting the growth of virus-transformed cells.

Autoimmune and other diseases contemplated to be treated include arthritis, psoriasis, bowel disease, juvenile diabetes, lupus, multiple sclerosis, gout and gouty arthritis, rheumatoid arthritis, rejection of transplantation, giant cell arteritis, allergy and asthma.

Still other contemplated uses of the compounds according to the present invention include use as intermediates in the chemical synthesis of other nucleoside or nucleotide analogs that are, in turn, useful as therapeutic agents or for other purposes.

In yet another aspect, a method of treating a mammal comprises administering a therapeutically and/or prophylactically effective amount of a pharmaceutical containing a compound of the present invention. In this aspect the effect may relate to modulation of some portion of the mammal's immune system, especially modulation of lymphokines profiles of Typel and Type 2 with respect to one another. Where modulation of Type 1 and Type 2 lymphokines occurs, it is particularly contemplated that the modulation may include suppression of both Type 1 and Type 2, and more preferably stimulation of Type llymphokines, or a relative increase of a type 1 response to a type 2 response.

Combination therapies according to the present invention comprise the administration of at least one compound of the present invention or a functional derivative thereof and at least one other pharmaceutically active ingredient. The active ingredient (s) and pharmaceutically active agents may be administered separately or together and when administered separately this may occur simultaneously or separately in any order. The amounts of the active ingredient (s) and pharmaceutically active agent (s) and the relative timings of administration will be selected in order to achieve the desired combined therapeutic effect. Preferably, the combination therapy involves the administration of one compound of the present invention or a physiologically functional derivative thereof and one of the agents mentioned herein below.

Examples of other drugs or active ingredients contemplated to be effective in combination with a modulator according to Formula (I) are anti-viral agents such as interferon, including but not limited to interferon α- and γ-, Ribavirin, acyclovir, and AZT™ ; anti-fungal agents such as tolnaftate, Fungizone™, Lotrimin™, Mycelex™, Nystatin and Amphoteracin ; anti-parasitics such as Mintezol™, Niclocide™, Vermox™, andFlagyl™, bowel agents such as Immodium™, Lomotil™ and Phazyme™ ; anti-tumor agents such as interferon α- and γ-, Adriamycin™, Cytoxan™, Itnuran ™, Methotrexate, Mithracin, TiazofurinT-Nl. Taxon; dermatologic agents such as Aclovate™, Cyclocort™, Denorex, Florone™, Oxsoralen™, coal tar and salicylic acid; migraine preparations such as ergotamine compounds; steroids and immunosuppresants not listed above, including cyclosporins, Diprosone™, hydrocortisone; Floron, Lidex, Topicort and Valisone ; and metabolic agents such as insulin, and other drugs which may not nicely fit into the above categories, including cytokines such as IL2, IL4, IL6, IL8, ILlO and IL12.

Especially preferred primary drugs are AZT, 3TC, 8-substituted guanosine analogs, 2,3-dideoxynucleosides, interleukin II, interferons such as α- and γ-interferons, tucaresol, levamisole, isoprinosine and cyclolignans. Other drugs that may be mentioned are Toll-like receptor (TLR) agonists, such as Actilon, other immunomodulators and protease/polymerase inhibitors.

Examples of such further therapeutic agents include agents that are effective for the modulation of immune system or associated conditions such as AZT, 3TC, 8- substituted guanosine analogs, 2', 3'-dideoxynucleosides, interleukin II, interferons, such as α-interferon, tucaresol, levamisole, isoprinosile and cyclolignans. Certain compounds according to the present invention may be effective for enhancing the biological activity of certain agents according to the present invention by reducing the metabolism or inactivation of other compounds and as such, are co-administered for this intended effect.

With respect to dosage, one of ordinary skill in the art will recognize that a therapeutically effective amount will vary with the infection or condition to be treated, its severity, the treatment regimen to be employed, the pharmacokinetics of the agent used, as well as the patient (animal or human) treated.

For the above mentioned uses the doses administered will, of course, vary with compound employed, the mode of administration and the treatment desired. However, in general, satisfactory results are obtained when the compound of formula (I) is administered at a daily dosage of from about 1 μg to about 20 mg per kg of animal body weight, preferably given in divided doses 1 to 4 times a day, e.g. twice a day (BID) or in sustained release form. For man the total daily dose is in the range of from 70 μg to 1 ,400 mg and unit dosage forms suitable for administration comprise from 20 μg to 1,400 mg of the compound admixed with a solid or liquid pharmaceutical diluent or carrier.

While treatment success may be achieved with some viral infections at relatively low plasma concentrations of the compounds of formula (I), other viral infections may require relatively high dosages. It is contemplated, however, that an appropriate regimen may be developed by administering a small amount, and then increasing the amount until the side effects become unduly adverse, or the intended effect is achieved. The compounds of formula (I) may be used on their own or in the form of appropriate pharmaceutical compositions for topical, enteral or parenteral administration.

Compositions in a form suitable for topical administration to the lung include aerosols, e.g. pressurised or non-pressurised powder compositions; compositions in a form suitable for oesophageal administration include tablets, capsules and dragees; compositions in a form suitable for administration to the skin include creams, e.g. oil- in-water emulsions or water-in-oil emulsions; compositions in a form suitable for administration intravenously include injections and infusions; and compositions in a form suitable for administration to the eye include drops and ointments.

According to the invention there is also provided a pharmaceutical composition comprising, preferably less than 80% and more preferably less than 50% by weight of, a compound of formula (I), or a pharmaceutically acceptable derivative thereof, in admixture with a pharmaceutically acceptable diluent or carrier. Examples of such diluents and carriers are: for tablets and dragees - lactose, starch, talc, stearic acid; for capsules - tartaric acid or lactose; and for injectable solutions - water, alcohols, glycerin, vegetable oils.

When the compound of formula (I) is to be administered to the lung it may be inhaled as a powder which may be pressurised or non-pressurised. Pressurised powder compositions of the compounds of formula (I) may contain a liquified gas propellant or a compressed gas. In non-pressurised powder compositions the active ingredient in finely divided form may be used in admixture with a larger-sized pharmaceutically acceptable carrier comprising particles of up to, for example, 100μm in diameter.

Suitable inert carriers include, e.g. crystalline lactose.

The compounds of formula (I) have the advantage that they are less toxic, more efficacious, are longer acting, have a broader range of activity, are more potent, produce fewer side effects, are more easily absorbed or have other useful pharmacological properties, than compounds of a similar structure. To prepare the pharmaceutical compositions according to the present invention, a therapeutically effective amount of one or more of the compounds according to the present invention is preferably intimately admixed with a pharmaceutically acceptable carrier according to conventional pharmaceutical compounding techniques to produce a dose. A carrier may take a wide variety of forms depending on the form of preparation desired for administration, e.g. oral or parenteral. In preparing pharmaceutical compositions in oral dosage form, any of the usual pharmaceutical media may be used. Thus, for liquid oral preparations such as suspensions, elixirs and solutions, suitable carriers and additives including water, glycols, oils, alcohols, flavouring agents, preservatives, colouring agents and the like may be used. For solid oral preparations such as powders, tablets, capsules, and for solid preparations such as suppositories, suitable carriers and additives including starches, sugar carrier, such as dextrose, mannitol, lactose and related carriers, diluents, granulating agents, lubricants, binders, disintegrating agents and the like may be used. If desired, the tablets or capsules may be enteric-coated or sustained release by standard techniques.

For parenteral formulations, the carrier will usually comprise sterile water or aqueous sodium chloride solution, though other ingredients including those that aid dispersion may be included. Of course, where sterile water is to be used and maintained as sterile, the compositions and carriers must also be sterilized. Injectable suspensions may also be prepared, in which case appropriate liquid carriers, suspending agents and the like may be employed.

The compounds of formula (I) have the advantage that they are less toxic, more efficacious, are longer acting, have a broader range of activity, are more potent, produce fewer side effects, are more easily absorbed or have other useful pharmacological properties, than compounds of a similar structure, in particular ribavirin.

In particular, we have found that the compounds of formula (I) are excluded from red blood cells, unlike ribavirin which is rapidly taken up and leads to anaemia. Blood partitioning of compounds of the invention and of ribavirin has been determined using whole human blood. Compounds, at a nominal concentration of 50μM were incubated at 37⁰C for up to 2 hours and concentrations determined in both the plasma and red blood cell fractions. Red cell samples were also treated with phosphatise to release potential phosphorylated parent compound and/or ribavirin which may have been formed.

Ribavirin was seen to enter red cells and accumulate as phophorylated ribavarin during the course of the 2 hour incubation. This accumulation was mirrored by a decrease in plasma ribavirin, such that the final ratio of total ribavirin in red cells to that in plasma was approximately 7:1. For the glycosylated ribavirin derivatives tested, red cell penetration was poor and there was no evidence that parent compounds or phosphorylated forms accumulated in the cells during the incubation. Indeed, the compounds of the invention showed higher concentrations in plasma than in red cells throughout the incubation, with red celhplasma ratios between 0.1:1 and 0.3:1 at 2 hours. No ribavirin was detected in any of these incubates.

This suggests that the compounds of the invention will be less toxic than ribavirin, may be used at both lower and higher doses, and for a longer treatment regime, than corresponding therapies with ribavirin.

In separate experiments, we have established the uptake of compounds of the invention into the HepG2 cell line, using a similar methodology to that described above.

Compounds 1, 2, 4, 5 and 8-19 appear stable in plasma.

Compounds 5-19 appear stable in simulated gastric fluid.

Compounds 6 and 7 enter Hep-G2 cells over a period of 90 minutes.

Compounds 6, 7, 15 and 16 liberate free ribavirin in Hep-G2 and SK-Hepl cells.

In particular, compounds 1-4, 20-23, 29 and 30 show inhibition of bovine viral diarrhea virus (BVDV) immunofocus formation. The method for testing the level of inhibition of BVDV immunofocus formation involves adding the compound and BVDV to a cover plate of bovine kidney cells. A control is set up in which ribavirin and BVDV are similarly added to a cover plate of bovine kidney cells. The cover plates are then left overnight. The percentage inhibition of BVDV immunofocus formation is expressed by comparing the degree of inhibition shown in the cover plate containing the compound against the inhibition shown in the control.

A more detailed description of the assay is as follows:

Method for BVDV assay

The appropriate number of 19mm coverslips were dipped in 70% ethanol, blotted and air dried in 12 well tissue culture plates. Each inhibitor and control Ribavirin was diluted to 5 mM in PBS. MDBK NBL cells (ATCC) were used between passages pi 16 and pi 25. Culture medium was aspirated from flask(s) and cells washed with PBS. An appropriate volume (~0.5ml/25cm²) Trypsin versine was added to the cells and incubated at 37°C/5% CO₂ until cells were detatched from the flask (3-5min). Cells were then resuspended in at least 5vol of cell culture medium. A viable cell count was performed by mixing 0.1 ml cell suspension with 0.1ml Trypan Blue. Viable and non- viable cells were counted in the three corner squares of a haemocytometer. The cells were then diluted to a density of 3.5 x 10⁵ / ml in cell culture medium. Stock BVDV (lot 1, ~3 x 10⁶ TCIU / ml) was added to the cell suspension to give a titre of - 6.5 x 10³ TCIU / ml. The diluted inhibitors were mixed with the cell/virus suspension to give a final inhibitor concentration of 50 μM (1 in 1000 dilution). For each inhibitor 750 μl volume of the cell/virus/inhibitor mix was added to 3 wells of the 12 well tissue culture plates containing ethanol washed coverslips. Plates were incubated at 5% CO₂; 37°C overnight. Working quickly to avoid drying of coverslips, cells were fixed and stained as follows.

Plates removed from incubator. Supernatant was removed by aspiration. 1 ml PBS added to wells and aspirated (x3 times per well). 0.5 ml 4% Paraformaldehyde in PBS added to each well and incubated 20 min at ambient temperature. 4% Paraformaldehyde was removed by aspiration. ImI PBS added to wells and aspirated (x3 times per well)

1 ml 0.1% Triton X100 in PBS added to each well and incubated 7 min at ambient temperature. 4% 0.1% Triton XlOO was removed by aspiration. 1 ml PBS added to wells and aspirated (x3 times per well). On the third wash, the PBS was not aspirated.

1° Antibody: Mouse anti-BVDV (Bovine Viral Diarrhoea Virus Type 1 E2 (gp53)) catalogue no. 157 VMRD.

Diluted 1:100 in PBS + 10% FCS.

For each coverslip to be stained, 30μl diluted antibody was placed on the upturned lid of a 12-well plate and the coverslips containing cells were carefully removed from the wells and placed face down over the diluted antibody droplet.

Coverslips were diluted with antibody 60 min at ambient temperature.

After incubation, coverslips were carefully lifted and returned face up to the 12 well dish containing ImI PBS per well.

2 ml PBS added to wells and aspirated (x3 times per well). On the third wash, the PBS was not aspirated.

2° Antibody: Alexa Fluor 594 conjugate donkey anti-mouse IgG monoclonal. Catalogue Number - A21203 (Molecular Probes, Invitrogen).

Diluted 1:200 in PBS + 10% FCS.

For each coverslip to be stained, 30μl diluted antibody was placed on the upturned lid of a 12-well plate and the coverslips containing cells were carefully removed from the wells and placed face down over the diluted antibody droplet. Coverslips were diluted with antibody 60 min at ambient temperature.

After incubation, coverslips were carefully lifted and returned face up to the 12 well dish containing ImI PBS per well.

2 ml PBS added to wells and aspirated (x4 times per well). On the fourth wash, the PBS was not aspirated.

Coverslips (in PBS) were viewed on a fluorescent microscope and cells displaying cytoplasmic fluorescence were counted.

Compound detection by MS-MS

Materials

All general solvents and reagents used for analyses performed by BioFocus DPI were of analytical or appropriate equivalent grade and were stored according to suppliers' recommendations. Any details of reagent suppliers and the equipment used in these experiments which are not detailed in this report, are held on file at BioFocus DPI, Cambridge, UK.

The glycosylated ribavirin derivatives were supplied as 5OmM solutions. These stock materials and any working solutions prepared from them were stored at approximately - 20⁰C.

Human plasma (Lot# 17-133) used in the assay was supplied, frozen, by SCIPAC (SCIPAC, Broad Oak Enterprise Village, Broad Oak Road, Sittingbourne, Kent, ME9 8AQ) and was stored at approximately -20⁰C prior to use.

Methods

Mass spectrometry

A Micromass Quattro Micro mass spectrometer (S/N: QAA028, Waters Ltd, 730-740 Centennial Court, Centennial Park, Hertfordshire) was used for this study. The settings of the electrospray ion source used for method development and subsequent data acquisition are detailed in Table 1 :

Table 1 : Instrument parameters

Parameter Setting

Capillary voltage (kV) 3.0

Extractor cone voltage

3 (V)

RF lens (V) 0.2

Source temp (oC) 120

Desolvation gas temp

250 (oC)

Desolvation gas flow

350 (L/h)

Cone gas flow (L/h) 100

Multiple reaction monitoring (MRM) methods were created using QuanOptimise software

(Waters Ltd 730-740 Centennial Court, Centennial Park, Hertfordshire.). The parameters selected are shown in Table 2.

Table 2: Compound tune parameters

Compound Ionisation Transition Cone Collision mode voltage energy

(V) (eV)

Ribavirin ESP+ 245.15 > 112.78 18 10

Compound 28 ESP+ 548.80 > 26 28 96.70

Compound 29 ESP+ 506.05 > 18 22 96.81

Compound 1 ESP+ 479.01 > 112.78 26 16

Compound 20 ESP+ 507.10 > 113.10 18 16

Compound 2 ESP+ 509.08 > 112.91 26 16

Compound 30 ESP+ 509.10 > 112.97 18 22

Compound 4 ESP+ 505.21 > 287.92 60 28

399.09

Compound 32 ESP+ 96.74 26 28 >

Methylcytidine ESP+ 258.18 > 125.89 18 10

Method files were created which contained the transitions (listed above in table 2) for the analyte, ribavirin and the analytical internal standard methylcytidine.

Chromatography

Chromatographic gradient methods previously developed for analysis of ribavirin and derivatives of ribavirin were used for these analyses.

The chromatographic conditions used are detailed in Table 3 and compound retention times in Table 4. Table 3: Chromatographic conditions

* Phenomenex column (Phenomenex, Melville House, Queens avenue, Hurdsfield Ind Est,

Macclesfield, SKlO 2BN)

Table 4: Chromatographic retention times

Once methods were created which contained working detection parameters for ribavirin, the novel derivatives and the internal standard 3 -methylcytidine, fresh dilutions in 50:50 (v/v) acetonitrile:water were made from the 5OmM stocks and the ribavirin content of these solutions was quantified.

This analysis indicated measurable levels of ribavirin to be present in stock solutions of Compounds 29 and 30. However, repeat injections of the 50:50 solvent solutions from the same vials indicated that the ribavirin content was increasing over a relatively short period (<3 hours) in this mixture. These results are shown in table 5.

Table 5: Ribavirin detected in 50μM dilutions prepared from stock supplies (dilutions in 50:50, v/v, acetontrile:water for MS)

Plasma Stability

Compound stock solutions, supplied at 5OmM, were diluted 1:500 in water to give 100μM working solutions.

Ribavirin and the standard compound, bisacodyl, were also diluted to 100μM in water. The aqueous working solutions were added (n=2) to human plasma (SCIPAC, Lot# 17- 133) at a final concentration oflOμM; initiating the incubations. The incubates were then transferred to a shaking water bath, maintained at 37oC.

Aliquots of plasma (50μl) were removed at prescribed time-points (0, 5, 15, 30 and 120 minutes), mixed with acetonitrile (100μl) and centrifuged at 4000rpm for 15 minutes prior to MS analysis of supernatant. As Compounds 29 and 30 had shown some instability in solution when awaiting MS analysis, the time between sampling of plasma incubates and processing via MS was kept to a minimum for these two compounds.

Red blood cell exclusion and plasma stability Materials

All general solvents and reagents used for analyses performed by BioFocus DPI were of analytical or appropriate equivalent grade and were stored according to suppliers' recommendations. Any details of reagent suppliers and the equipment used in these experiments which are not detailed in this report, are held on file at BioFocus DPI, Cambridge, UK.

The glycosylated ribavirin derivatives were supplied as 5OmM solutions. These stock materials and any working solutions prepared from them were stored at approximately - 20°C.

Whole human blood (Batch# HHB4584) used in the assay was supplied, refrigerated, by First Link (First Link (UK) Ltd, 1 Vale Pits Road, Garretts Green, Birmingham, B33 OTD) and used immediately on receipt at BioFocus DPI (Thursday, May 17, 2007).

Methods

Mass spectrometry

A Micromass Quattro Micro mass spectrometer (S/N: QAA028, Waters Ltd, 730-740

Centennial Court, Centennial Park, Hertfordshire) was used for this study. The settings of the electrospray ion source and the individual parameters for acquisition of compound data are given above.

Chromatography

Chromatographic gradient methods previously developed for analysis of ribavirin and derivatives of ribavirin were used for these analyses.

Blood Partitioning Compound stock solutions, supplied at 5OmM, were diluted 1:1000 (n=2) in whole blood (pre-warmed to 37oC) to give 50μM incubations.

Incubations were mixed by inversion several times, the T=O sample was removed and the sample tubes were transferred to an orbital shaker in an incubator maintained at 37°C .

Aliquots of blood (ImI) were subsequently removed at prescribed time-points (30, 60 and 120 minutes), and centrifuged at 15000rpm for 5 minutes to separate plasma and red cells.

Samples of plasma were analysed directly; samples from the red cell pellets were lysed using ice-cold, purified water. 100μl aliquots of both cell lysate and plasma were then mixed with 200μl of acetonitrile to precipitate protein and extract compounds.

Blood Partitioning Experimental Procedure

1. Whole human blood pre-incubated at 37oC.

2. Compounds added to blood to give a nominal compound concentration of 50μM

3. ImI of blood removed per time point (0, 30, 60 and 120minutes)

4. Blood transferred to Eppendorf tube and centrifuged at 150Og for 5 minutes at 4⁰C (rotor pre-chilled) 5. 400μl of plasma transferred immediately to 96 deepwell plate

6. 300μl of red blood cells transferred with a positive displacement pipette to fresh Eppendorf tube

7. ImI ice-cold water added

8. Samples vortexed for 30 seconds followed by brief centrifugation

Plasma Analysis 100μl of plasma removed

200μl of acetonitrile added Samples centrifuged and supernatant analysed

Red Blood Cell Analysis 100μl lysate removed 200μl of acetonitrile added

Samples centrifuged and supernatant analysed

Plasma concentrations are illustrated in Figure 5. These show that plasma concentrations of both ribavirin and Compound 32 rapidly decrease, suggesting uptake.

Red blood cell concentrations are illustrated in Figure 6. Both ribavirin and Compound 32 rapidly increase, suggesting uptake. The levels then decrease, suggesting phosphorylation.

Compound 32 is freely permeable into Hep-G2 and SK-Hepl cells and releases ribavirin within the cells.

In particular, compounds 1, 2, 4, 20 and 28 show plasma stability over a period of 120 minutes.

Claims

Claims

1. A compound of formula (I),

(I)

wherein, at least one of R¹, R² and R³ represents a group S-L- and the remainder represent H; S represents a binding group; L represents a linker chain; X represents O or NH; and pharmaceutically acceptable derivatives thereof.

2. A compound according to claim 1, wherein S represents one of the following groups:

(II) (III) (IV) wherein, one of A and A' represents L and the other represents H; or A is L and -D-A' represents -OH, -OAcyl or -NHAcyl; or A represents H and D represents NH and A' represents L; and in each case, R⁴ represents Acyl or H; R⁵ = OH; u represents an integer from 0-3 inclusive; and L is as defined in claim 1.

3. A compound according to claim 1, wherein

X represents O and either or both of R² and R³ represent S-L-; or X represents O or NH and R¹ represents S-L-.

4. A compound according to claim 1, wherein L includes COCH₂-, CO- or benzylene which is linked to -O- or -X- of the ribavirin moiety.

5. A compound according to claim 1, wherein R¹ represents L; R² and R³ each represent H.

6. A compound according to claim 1, wherein X represents O; R¹ represents H; R² represents L; R³ represents H.

7. A compound according to claim 1, wherein X represents O; R¹ represents H; R² represents H; R³ represents L.

8. A compound according to claim 1, wherein X represents O; R¹ represents H; R² represents L; R³ represents L.

9. A compound according to claim 1, wherein S represents an oligosaccharide terminating in a galactosamine or galactose residue.

10. A compound according to claim 1 or 9, wherein S represents galactosamine, galactose or lactose.

11. A compound according to claim 1, wherein L is further substituted by S', where S' has the same definition as S defined in claim 1.

12. A compound according to claim 11, wherein S represents galactosamine, galactose or lactose.

13. A compound according to any preceding claim, wherein S binds to an asialoglycoprotein receptor.

14. A compound according to claim 1, wherein L represents one of the following groups:

wherein, n = 0 to 6; Y = O; -OCH₂-; -(CR⁶R⁷)_d-, where R⁶ and R⁷ independently represent H or alkyl; cycloalkylene; arylene; or single bond; and d = 0 to 6;

or

(V) wherein, p and z independently = 1 or 2; s = 1 to 4; b, c, r and t independently = 0 to 3; Q and Q' independently = -(CR⁶R⁷)_qCONH-, where R⁶ and R⁷ are as defined above, and q = 1 or 2; or a single bond; T = CH or N; U = single bond, -CONH- or -CO-;

or

(VI) wherein,

E = -(CR⁶R⁷)_q-, where R⁶ and R⁷ are as defined above, q is as defined above; or benzylene; Z = single bond, -CO-, -NHCO(CH₂)_r-, wherein r is as defined above;

or

(VII)

w = 0 or 1; q is as defined above; U = -CO- or -CONH-;

Z' = -ONHCO-CH₂-

or H; and

S is as defined in claim 1.

15. A compound according to claim 1, wherein L represents one of the following groups:

wherein r and n are as defined as in claim 14; and S is as defined in claim 1.

16. A compound according to claim 1, which is: Compound 1

Compound 2

Compound 3

Compound 4

17. A compound according to claim 1, which is: Compound 5

Compound 6

Compound 7

Compound 8

Compound 9

Compound 10

Compound 11

Compound 12

Compound 13

Compound 14

Compound 15

Compound 16

Compound 17

Compound 18

Compound 19

Compound 20

Compound 21

Compound 22

Compound 23

Compound 24

Compound 25

Compound 26

Compound 27

Compound 28

Compound 29

Compound 30

Compound 31

Compound 32

18. A composition comprising a compound of claim 1.

19. Use of a compound of claim 1 as a medicament.