AU2005273726A1 - Arene ruthenium (II) compounds and their use in cancer therapy - Google Patents

Description

WO 2006/018649 PCT/GB2005/003242 ARENE RUTHENIUM (II) COMPOUNDS AND THEIR USE IN CANCER THERAPY This invention relates to ruthenium (11) compounds, to their use in medicine, particularly for the treatment and/or prevention of cancer, and to a process for their preparation. 5 WO 01/30790 and WO 02/02572 disclose ruthenium (II) compounds for use in the treatment of cancer. These compounds can be described as half-sandwich compounds, having an arene ring bound to the ruthenium, as well as other non-arene ligands. The compounds exemplified in these applications have as one of the ligands a halo atom. 10 Without wishing to be bound by theory, it is thought that the hydrolysis of the halo atom activates the complexes and allows them to bind to DNA. The present inventors have studied the hydrolysis rates of a number of different ligands including halo and have surprisingly found that complexes containing ligands that have 15 longer hydrolysis times still exhibit anti-tumour activity. According to the present invention there is provided a ruthenium (II) compound of formula (I): fM+ R 32 y R R J_ Ru x A (C'), B . r (I) 20 or a solvate or prodrug thereof, wherein: R', R 2 , R 3 , R 4 , R 5 and R 6 are independently selected from H, C 1

..

7 alkyl, C.

20 aryl, C3-20 heterocyclyl, halo, ester, amido, acyl, sulfo, sulfonamido, ether, thioether, azo, amino, or

R

1 and R 2 together with the ring to which they are attached form a saturated or unsaturated carbocyclic or heterocyclic group containing up to three 3- to 8- membered 25 carbocyclic or heterocyclic rings, wherein each carbocyclic or heterocyclic ring may be fused to one or more other carbocyclic or heterocyclic rings; X is a neutral or negatively charged N- or S- donor ligand; WO 2006/018649 PCT/GB2005/003242 2 Y is a counterion; m is 0 or 1; q is 1, 2 or 3; C' is C 1

-

12 alkylene bound to two A groups; 5 pisOorl and ris 1 when pis0and ris2when pisl; and A and B are each independently O-donor, N-donor or S-donor ligands. When p is 1, the ligand A is bound to another ligand A such that the compound comprises two ruthenium atoms. Such complexes are called dinuclear complexes. 10 Ligands A and B may be connected to one another, but they cannot be bound to ligand X. A second aspect of the present invention provides a composition comprising a 15 compound of the first aspect and a pharmaceutically acceptable carrier or diluent. A third aspect of the invention provides the use of a compound of the first aspect in a method of therapy. 20 A fourth aspect of the invention provides the use of a compound of the first aspect in the preparation of a medicament for the treatment of cancer. A fifth aspect of the invention provides a method of treatment of a subject suffering from cancer, comprising administering to such a subject a therapeutically-effective amount of 25 a compound of the first aspect, preferably in the form of a pharmaceutical composition. Definitions N-donor ligands: N-donor ligands are ligands which bind to a metal atom via a nitrogen atom. They are well known in the art and include: nitrile ligands (N=C-R); azo ligands 30 (N=N-R); aromatic N-donor ligands; amine ligands (NRN1RN 2

RN

3 ); azide (N 3 ~); cyanide (NEC~); isothiocyanate (NCS~). In both nitrile and azo ligands R may be selected from C 17 alkyl and C 5

-

20 aryl.

WO 2006/018649 PCT/GB2005/003242 3 Aromatic N-donor ligands include optionally substituted pyridine, pyridazine, pyrimidine, purine and pyrazine. The optional substituents may be selected from cyano, halo and

C

1

.

7 alkyl. 5 RN 1 , RN 2 and RN 3 may be independently selected from H and C 1

.

7 alkyl, or if A and B are both amine ligands, RN1 on each ligand join together to form a C1.7 alkylene chain. When p is 1, RN 2 on each A ligand join together form the group C' which is C 1

-

1 2 alkylene. 10 S-donor ligands: S-donor ligands are ligands which bind to a metal atom via a sulphur atom. They are well known in the art and include: thiosulfate (S2032-); isothiocyanate (NCS~); thiocyanate (CNS~); sulfoxide ligands (RSIRS 2 SO); thioether ligands (Rs 1

R

52 S); thiolate ligands (Rs'S~); sulfinate ligands (Rs1SO2~); and sulfenate ligands (Rs1SO~), wherein RSl and RS 2 are independently selected from C1.7 alkyl and C5-20 aryl, which 15 groups may be optionally substituted. O-donor ligands: 0-donor ligands are ligands which bind to a metal atom via an oxygen atom. They are well known in the art and include: carbonate (C03-); carboxylate ligands (RcC02-); nitrate (NO 3 ); sulfate (S0 4 2 -) and sulphonate (Rs403~), wherein Rc is selected 20 from C 1

.

7 alkyl and Cs- 20 aryl and Rs' is as defined above. C1.7 Alkyl: The term "C1.7 alkyl", as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a carbon atom of a hydrocarbon compound having from 1 to 7 carbon atoms, which may be aliphatic or alicyclic, and which may be 25 saturated or unsaturated (e.g., partially unsaturated, fully unsaturated). Thus, the term "alkyl" includes the sub-classes alkenyl, alkynyl, cycloalkyl, cycloalkyenyl, cylcoalkynyl, etc., discussed below. Examples of saturated C1.7 alkyl groups include, but are not limited to, methyl (C 1 ), ethyl 30 (C2), propyl (C 3 ), butyl (C 4 ), pentyl (C 5 ), hexyl (C6) and heptyl (C). Examples of saturated linear C1.7 alkyl groups include, but are not limited to, methyl (CI), ethyl (C2), n-propyl (C 3 ), n-butyl (C4), n-pentyl (amyl) (C 5 ), n-hexyl (C 6 ), and n-heptyl (C7).

WO 2006/018649 PCT/GB2005/003242 4 Examples of saturated branched C17 alkyl groups include iso-propyl (C 3 ), iso-butyl (C 4 ), sec-butyl (C4), tert-butyl (C4), iso-pentyl (C5), and neo-pentyl (C5).

C

2

.

7 Alkenyl: The term "C2.7 alkenyl", as used herein, pertains to an alkyl group having 5 one or more carbon-carbon double bonds. Examples of C27 alkenyl groups include, but are not limited to, ethenyl (vinyl, -CH=CH 2 ), 1-propenyl (-CH=CH-CH 3 ), 2-propenyl (allyl,

-CH-CH=CH

2 ), isopropenyl (1-methylvinyl, -C(CH 3

)=CH

2 ), butenyl (C4), pentenyl (C), and hexenyl (0W). 10 C 2

.

7 Alkynyl: The term "C 2

.

7 alkynyl", as used herein, pertains to an alkyl group having one or more carbon-carbon triple bonds. Examples of C2-7 alkynyl groups include, but are not limited to, ethynyl (ethinyl, -CECH) and 2-propynyl (propargyl, -CH 2 -C=CH). C3.7 Cycloalkyl: The term "C3.7 cycloalkyl", as used herein, pertains to an alkyl group 15 which is also a cyclyl group; that is, a monovalent moiety obtained by removing a hydrogen atom from an alicyclic ring atom of a carbocyclic ring of a carbocyclic compound, which carbocyclic ring may be saturated or unsaturated (e.g., partially unsaturated, fully unsaturated), which moiety has from 3 to 7 carbon atoms. Thus, the term "C3-7 cycloalkyl" includes the sub-classes cycloalkyenyl and cycloalkynyl. Examples 20 of cycloalkyl groups include, but are not limited to, those derived from: saturated hydrocarbon compounds: cyclopropane (C3), cyclobutane (C4), cyclopentane (Cs), cyclohexane (C), cycloheptane (C7), methylcyclopropane (04), dimethylcyclopropane (C), methylcyclobutane (C), dimethylcyclobutane (C6), methylcyclopentane (C6), dimethylcyclopentane (C) 25 methylcyclohexane (C7); and unsaturated hydrocarbon compounds: cyclopropene (C3), cyclobutene (C4), cyclopentene (C), cyclohexene (C), methylcyclopropene (04), dimethylcyclopropene (C), methylcyclobutene (C5), dimethylcyclobutene (C6), methylcyclopentene (C), dimethylcyclopentene (C7). 30 The alkyl groups in the compounds of the invention may optionally be substituted. Substituents include one or more further alkyl groups and/or one or more further substituents, such as, for example, C5-20 aryl (e.g. benzyl), C3-20 heterocyclyl, cyano ( CN), nitro (-NO 2 ), hydroxyl (-OH), ester, halo, thiol (-SH), thioether and sulfonate (- WO 2006/018649 PCT/GB2005/003242 5 S(=0) 2 )OR, where R is wherein R is a sulfonate substituent, for example, a C 1 -7 alkyl group, a C3.20 heterocyclyl group, or a C 5

-

20 aryl group, preferably a C1-7 alkyl group). C2-12 alkylene: The term "C2-12 alkylene" is defined similarly to the definition of the term 5 "alkyl" but includes C2 to C12 groups and is a divalent species with radicals separated by two or more (e.g. from two to twelve) carbon atoms linked in a chain. Preferably, the alkylene groups are straight chain groups. C 2

-

12 alkylene groups are optionally substituted in the akylene chain, preferably with one or more phenylene (eg, 1-4 phenylene) and/or -CONRIa groups and/or -NR 2 a- groups, where RI" and R 2 , 10 independently represent H, C1.7 alkyl, C3-20 heterocyclyl or C 5

-

20 aryl. Preferably, Ri" and R2a are H or C1 to C3 alkyl. C-20 Aryl: The term "C.20 aryl", as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from an aromatic ring atom of an aromatic 15 compound, which moiety has from 3 to 20 ring atoms. Preferably, each ring has from 5 to 7 ring atoms. In this context, the prefixes (e.g., C320, C-7, C5.6, etc.) denote the number of ring atoms, or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, 20 the term "C-6 aryl", as used herein, pertains to an aryl group having 5 or 6 ring atoms. The ring atoms may be all carbon atoms, as in "carboaryl groups". Examples of carboaryl groups include C3.20 carboaryl, C5-20 carboaryl, C5.15 carboaryl, C.12 carboaryl, C-10 carboaryl, C-7 carboaryl, C-6 carboaryl, C5 carboaryl, and C6 carboaryl. 25 Examples of carboaryl groups include, but are not limited to, those derived from benzene (i.e., phenyl) (C6), naphthalene (C1o), azulene (Clo), anthracene (C14), phenanthrene (C14), naphthacene (C18), and pyrene (C16). 30 Examples of aryl groups which comprise fused rings, at least one of which is an aromatic ring, include, but are not limited to, groups derived from indane (e.g., 2,3-dihydro-1H indene) (Cs), indene (C), isoindene (C), tetraline (1,2,3,4-tetrahydronaphthalene (C0o), acenaphthene (C12), fluorene (C13), phenalene (C13), acephenanthrene (C15), and aceanthrene (C16).

WO 2006/018649 PCT/GB2005/003242 6 Alternatively, the ring atoms may include one or more heteroatoms, as in "heteroaryl groups". Examples of heteroaryl groups include C3-20 heteroaryl, C5.20 heteroaryl, C 5

.

1 5 heteroaryl, C5-12 heteroaryl, C 5

.

1 0 heteroaryl, C5.7 heteroaryl, C5 heteroaryl, C5 heteroaryl, 5 and C6 heteroaryl. Examples of monocyclic heteroaryl groups include, but are not limited to, those derived from:

N

1 : pyrrole (azole) (CP), pyridine (azine) (C6); 10 01: furan (oxole) (C);

S

1 : thiophene (thiole) (C5);

N

1 0 1 : oxazole (C), isoxazole (Cs), isoxazine (C6);

N

2 0 1 : oxadiazole (furazan) (C5);

N

3 0 1 : oxatriazole (C5); 15 N 1

S

1 : thiazole (C), isothiazole (C);

N

2 : imidazole (1,3-diazole) (C), pyrazole (1,2-diazole) (C), pyridazine (1,2-diazine) (C6), pyrimidine (1,3-diazine) (C6) (e.g., cytosine, thymine, uracil), pyrazine (1,4-diazine) (C6);

N

3 : triazole (C), triazine (C6); and,

N

4 : tetrazole (C5). 20 Examples of heteroaryl groups which comprise fused rings, include, but are not limited to: C9 heteroaryl groups (with 2 fused rings) derived from benzofuran (01), isobenzofuran (01), indole (N 1 ), isoindole (N 1 ), indolizine (N 1 ), indoline (N 1 ), isoindoline 25 (N 1 ), purine (N 4 ) (e.g., adenine, guanine), benzimidazole (N 2 ), indazole (N 2 ), benzoxazole

(N

1 0 1 ), benzisoxazole (N101), benzodioxole (02), benzofurazan (N 2 0 1 ), benzotriazole

(N

3 ), benzothiofuran (S 1 ), benzothiazole (N 1

S

1 ), benzothiadiazole (N 2 S); C10 heteroaryl groups (with 2 fused rings) derived from chromene (01), isochromene (01), chroman (01), isochroman ( 0 1), benzodioxan (02), quinoline (N 1 ), 30 isoquinoline (N 1 ), quinolizine (N 1 ), benzoxazine (N 1 0 1 ), benzodiazine (N 2 ), pyridopyridine (N 2 ), quinoxaline (N 2 ), quinazoline (N 2 ), cinnoline (N 2 ), phthalazine (N 2 ), naphthyridine (N 2 ), pteridine (N 4 ); C11 heteroaryl groups (with 2 fused rings) derived from benzodiazepine (N 2

);

WO 2006/018649 PCT/GB2005/003242 7 C13 heteroaryl groups (with 3 fused rings) derived from carbazole (N 1 ), dibenzofuran (01), dibenzothiophene (S 1 ), carboline (N 2 ), perimidine (N 2 ), pyridoindole

(N

2 ); and, C14 heteroaryl groups (with 3 fused rings) derived from acridine (N 1 ), xanthene 5 (01), thioxanthene (SI), oxanthrene (02), phenoxathiin (01S1), phenazine (N 2 ), phenoxazine (N 1 0 1 ), phenothiazine (N 1

S

1 ), thianthrene (S 2 ), phenanthridine (N 1 ), phenanthroline (N 2 ), phenazine (N 2 ). C-20 aryl groups may optionally be substituted with one or more substituents including, 10 for example, C 1

-

7 alkyl, Cs..20 aryl, C 3

-

20 heterocyclyl, cyano, nitro, hydroxyl, ester, halo, thiol, thioether and sulfonate. C320 Heterocyclyl: The term "C320 heterocyclyl", as used herein, pertains to a monovalent moiety obtained by removing a hydrogen atom from a ring atom of a 15 heterocyclic compound, which moiety has from 3 to 20 ring atoms, of which from 1 to 10 are ring heteroatoms. Preferably, each ring has from 3 to 7 ring atoms, of which from 1 to 4 are ring heteroatoms. In this context, the prefixes (e.g., C 3

.

2 0 , C 3

.

7 , C5., etc.) denote the number of ring atoms, 20 or range of number of ring atoms, whether carbon atoms or heteroatoms. For example, the term "C- 6 heterocyclyl", as used herein, pertains to a heterocyclyl group having 5 or 6 ring atoms. Examples of groups of heterocyclyl groups include C3-20 heterocyclyl, C5-20 heterocyclyl, C3.15 heterocyclyl, C5.15 heterocyclyl, C3-12 heterocyclyl, C5-12 heterocyclyl, C3.10 heterocyclyl, C-10 heterocyclyl, C3-7 heterocyclyl, C5-7 heterocyclyl, and C5.6 25 heterocyclyl. Examples of monocyclic heterocyclyl groups include, but are not limited to, those derived from:

N

1 : aziridine (C3), azetidine (C4), pyrrolidine (tetrahydropyrrole) (C5), pyrroline (e.g., 30 3-pyrroline, 2,5-dihydropyrrole) (Cs), 2H-pyrrole or 3H-pyrrole (isopyrrole, isoazole) (C5), piperidine (C), dihydropyridine (C6), tetrahydropyridine (C6), azepine (C7); 01: oxirane (C3), oxetane (C4), oxolane (tetrahydrofuran) (C5), oxole (dihydrofuran) (Cs), oxane (tetrahydropyran) (C), dihydropyran (C), pyran (C), oxepin (C7); WO 2006/018649 PCT/GB2005/003242 8

S

1 : thiirane (C 3 ), thietane (C4), thiolane (tetrahydrothiophene) (C 5 ), thiane (tetrahydrothiopyran) (C), thiepane (07); 02: dioxolane (C5), dioxane (C), and dioxepane (7); 03: trioxane (C6); 5 N 2 : imidazolidine (C), pyrazolidine (diazolidine) (C), imidazoline (C 5 ), pyrazoline (dihydropyrazole) (C5), piperazine (C6);

N

1 0 1 : tetrahydrooxazole (C 5 ), dihydrooxazole (Cs), tetrahydroisoxazole (C 5 ), dihydroisoxazole (C 5 ), morpholine (C), tetrahydrooxazine (C6), dihydrooxazine (C), oxazine (C6); 10 N 1

S

1 : thiazoline (C5), thiazolidine (C5), thiomorpholine (C6);

N

2 0 1 : oxadiazine (C6); 0 1

S

1 : oxathiole (Cs) and oxathiane (thioxane) (C6); and

N

1 0 1

S

1 : oxathiazine (C6). 15 C3-20 heterocyclyl groups may optionally be substituted with one or more substituents including, for example, C1.7 alkyl, C-20 aryl, C3.20 heterocyclyl, cyano, nitro, hydroxyl, ester, halo, thiol, thioether and sulfonate. Halo: -F, -Cl, -Br, and -1. 20 Ester (carboxylate, carboxylic acid ester, oxycarbonyl): -C(=0)OR, wherein R is an ester substituent, for example, a C1.7 alkyl group, a C3-20 heterocyclyl group, or a C-20 aryl group, preferably a C1.7 alkyl group. Examples of ester groups include, but are not limited to, -C(=0)OCH 3 , -C(=O)OCH 2

CH

3 , -C(=0)OC(CH 3

)

3 , and -C(=0)OPh. 25 Amino: -NR 1

R

2 , wherein R 1 and R 2 are independently amino substituents, for example, hydrogen, a C1.7 alkyl group (also referred to as C1.7 alkylamino or di-C 1

.

7 alkylamino), a C3-20 heterocyclyl group, or a C-20 aryl group, preferably H or a C1.7 alkyl group, or, in the case of a "cyclic" amino group, R 1 and R 2 , taken together with the nitrogen atom to which 30 they are attached, form a heterocyclic ring having from 4 to 8 ring atoms. Amino groups may be primary (-NH 2 ), secondary (-NHR 1 ), or tertiary (-NHR 1

R

2 ), and in cationic form, may be quaternary (-*NR'R 2

R

3 ). Examples of amino groups include, but are not limited to, -NH 2 , -NHCH 3 , -NHC(CH 3

)

2 , -N(CH 3

)

2 , -N(CH 2

CH

3

)

2 , -NHCH 2 Ph and -NHPh.

WO 2006/018649 PCT/GB2005/003242 9 Examples of cyclic amino groups include, but are not limited to, aziridino, azetidino, pyrrolidino, piperidino, piperazino, morpholino, and thiomorpholino. 5 Amido (carbamoyl, carbamyl, aminocarbonyl, carboxamide): -C(=O)NRR 2 , wherein R' and R 2 are independently amino substituents, as defined for amino groups. Examples of amido groups include, but are not limited to, -C(=O)NH 2 , -C(=O)NHCH 3 , -C(=O)N(CH 3

)

2 ,

-C(=O)NHCH

2

CH

3 , and -C(=O)N(CH 2

CH

3

)

2 , as well as amido groups in which R 1 and R 2 , together with the nitrogen atom to which they are attached, form a heterocyclic structure 10 as in, for example, piperidinocarbonyl, morpholinocarbonyl, thiomorpholinocarbonyl, and piperazinocarbonyl. Acyl (keto): -C(=O)R, wherein R is an acyl substituent, for example, a C1-7 alkyl group (also referred to as C1.7 alkylacyl or C1-7 alkanoyl), a C3-2o heterocyclyl group (also 15 referred to as C3.20 heterocyclylacyl), or a C520 aryl group (also referred to as C-20 arylacyl), preferably a C 1

.

7 alkyl group. Examples of acyl groups include, but are not limited to, -C(=O)CH 3 (acetyl), -C(=O)CH 2

CH

3 (propionyl), -C(=O)C(CH 3

)

3 (t-butyryl), and -C(=O)Ph (benzoyl, phenone). 20 Sulfo: -S(=0) 2 0H, -SO 3 H. Sulfonamido (sulfinamoyl; sulfonic acid amide; sulfonamide): -S(=0) 2

NRR

2 , wherein R, and R 2 are independently amino substituents, as defined for amino groups. Examples of sulfonamido groups include, but are not limited to, -S(=0) 2

NH

2 , -S(=O) 2

NH(CH

3 ), 25 -S(=0) 2

N(CH

3

)

2 , -S(=O) 2

NH(CH

2

CH

3 ), -S(=0) 2

N(CH

2

CH

3

)

2 , and -S(=0) 2 NHPh. Ether: -OR, wherein R is an ether substituent, for example, a C1-7 alkyl group (also referred to as a C1.7 alkoxy group), a C3-20 heterocyclyl group (also referred to as a C3-20 heterocyclyloxy group), or a C520 aryl group (also referred to as a C5.20 aryloxy group), 30 preferably a C1.7 alkyl group. Thioether (sulfide): -SR, wherein R is a thioether substituent, for example, a C1.7 alkyl group (also referred to as a C1.7 alkylthio group), a C320 heterocyclyl group, or a C520 aryl WO 2006/018649 PCT/GB2005/003242 10 group, preferably a C 1

.

7 alkyl group. Examples of C1.7 alkylthio groups include, but are not limited to, -SCH 3 and -SCH 2

CH

3 . Azo: -N=N-R, where R is an azo substituent, for example a C 1

.

7 alkyl group, a C3-20 5 heterocyclyl group, or a C 5

.

2 0 aryl group, preferably a C1.7 alkyl group. Examples of azo groups include, but are not limited to, -N=N-CH 3 and -N=N-Ph. Heterocyclic ring: The term "heterocyclic ring" as used herein refers to a 3-, 4-, 5-, 6-, 7-, or 8- (preferably 5-, 6- or 7-) membered saturated or unsaturated ring, which may be 10 aromatic or non-aromatic, containing from one to three heteroatoms independently selected from N, 0 and S, e.g. indole (also see above). Carbocyclic ring: The term "carbocyclic ring" as used herein refers to a saturated or unsaturated ring, which may be aromatic or non-aromatic, containing from 3 to 8 carbon 15 atoms (preferably 5 to 7 carbon atoms) and includes, for example, cyclopropane, cyclobutane, cyclopentane, cyclohexane and cycloheptane (also see above). Includes Other Forms Unless otherwise specified, included in the above are the well known ionic, solvate, and 20 protected forms of these substituents. For example, a reference to carboxylic acid (-COOH) also includes the anionic (carboxylate) form (-COO~) or solvate thereof, as well as conventional protected forms. Similarly, a reference to an amino group includes the protonated form (-N*HR 1

R

2 ) or solvate of the amino group, as well as conventional protected forms of an amino group. Similarly, a reference to a hydroxyl group also 25 includes the anionic form (-O~) or solvate thereof, as well as conventional protected forms. Isomers Certain compounds may exist in one or more particular geometric, optical, enantiomeric, 30 diasteriomeric, epimeric, atropic, stereoisomeric, tautomeric, conformational, or anomeric forms, including but not limited to, cis- and trans-forms; E- and Z-forms; c-, t-, and r forms; endo- and exo-forms; R-, S-, and meso-forms; D- and L-forms; d- and I-forms; (+) and (-) forms; keto-, enol-, and enolate-forms; syn- and anti-forms; synclinal- and anticlinal-forms; a- and p-forms; axial and equatorial forms; boat-, chair-, twist-, WO 2006/018649 PCT/GB2005/003242 11 envelope-, and halfchair-forms; and combinations thereof, hereinafter collectively referred to as "isomers" (or "isomeric forms"). Note that, except as discussed below for tautomeric forms, specifically excluded from the 5 term "isomers," as used herein, are structural (or constitutional) isomers (i.e., isomers which differ in the connections between atoms rather than merely by the position of atoms in space). For example, a reference to a methoxy group, -OCH 3 , is not to be construed as a reference to its structural isomer, a hydroxymethyl group, -CH 2 OH. Similarly, a reference to ortho-chlorophenyl is not to be construed as a reference to its 10 structural isomer, meta-chlorophenyl. However, a reference to a class of structures may well include structurally isomeric forms falling within that class (e.g., C 1

.

7 alkyl includes n-propyl and iso-propyl; butyl includes n-, iso-, sec-, and tert-butyl; methoxyphenyl includes ortho-, meta-, and para-methoxyphenyl). 15 The above exclusion does not pertain to tautomeric forms, for example, keto-, enol-, and enolate-forms, as in, for example, the following tautomeric pairs: keto/enol (illustrated below), imine/enamine, amide/imino alcohol, amidine/amidine, nitroso/oxime, thioketone/enethiol, N-nitroso/hydroxyazo, and nitro/aci-nitro. 1 ,OH H O --- =C=C :Zs2 C=C' H+ keto enol enolate 20 Note that specifically included in the term "isomer" are compounds with one or more isotopic substitutions. For example, H may be in any isotopic form, including 1 H, 2 H (D), and 3 H (T); C may be in any isotopic form, including 12C, 13 C, and 14C; 0 may be in any isotopic form, including 160 and 180; and the like. 25 Unless otherwise specified, a reference to a particular compound includes all such isomeric forms, including (wholly or partially) racemic and other mixtures thereof, for example, a mixture enriched in one enantiomer. Methods for the preparation (e.g., asymmetric synthesis) and separation (e.g., fractional crystallisation and 30 chromatographic means) of such isomeric forms are either known in the art or are readily obtained by adapting the methods taught herein, or known methods, in a known manner.

WO 2006/018649 PCT/GB2005/003242 12 Solvates It may be convenient or desirable to prepare, purify, and/or handle a corresponding solvate of the active compound. The term "solvate" is used herein in the conventional sense to refer to a complex of solute (e.g., active compound, salt of active compound) 5 and solvent. If the solvent is water, the solvate may be conveniently referred to as a hydrate, for example, a mono-hydrate, a di-hydrate, a tri-hydrate, etc. Unless otherwise specified, a reference to a particular compound also include solvate forms thereof. 10 Chemically Protected Forms It may be convenient or desirable to prepare, purify, and/or handle the active compound in a chemically protected form. The term "chemically protected form" is used herein in the conventional chemical sense and pertains to a compound in which one or more 15 reactive functional groups are protected from undesirable chemical reactions under specified conditions (e.g., pH, temperature, radiation, solvent, and the like). In practice, well known chemical methods are employed to reversibly render unreactive a functional group, which otherwise would be reactive, under specified conditions. In a chemically protected form, one or more reactive functional groups are in the form of a protected or 20 protecting group (also known as a masked or masking group or a blocked or blocking group). By protecting a reactive functional group, reactions involving other unprotected reactive functional groups can be performed, without affecting the protected group; the protecting group may be removed, usually in a subsequent step, without substantially affecting the remainder of the molecule. See, for example, Protective Groups in Organic 25 Synthesis (T. Green and P. Wuts; 3rd Edition; John Wiley and Sons, 1999). Unless otherwise specified, a reference to a particular compound also includes chemically protected forms thereof. 30 A wide variety of such "protecting," "blocking," or "masking" methods are widely used and well known in organic synthesis. For example, a compound which has two nonequivalent reactive functional groups, both of which would be reactive under specified conditions, may be derivatized to render one of the functional groups "protected," and therefore unreactive, under the specified conditions; so protected, the WO 2006/018649 PCT/GB2005/003242 13 compound may be used as a reactant which has effectively only one reactive functional group. After the desired reaction (involving the other functional group) is complete, the protected group may be "deprotected" to return it to its original functionality. 5 For example, a hydroxy group may be protected as an ether (-OR) or an ester (-OC(=O)R), for example, as: a t-butyl ether; a benzyl, benzhydryl (diphenylmethyl), or trityl (triphenylmethyl) ether; a trimethylsilyl or t-butyldimethylsilyl ether; or an acetyl ester

(-OC(=O)CH

3 , -OAc). 10 For example, an aldehyde or ketone group may be protected as an acetal (R-CH(OR) 2 ) or ketal (R 2

C(OR)

2 ), respectively, in which the carbonyl group (>C=O) is converted to a diether (>C(OR) 2 ), by reaction with, for example, a primary alcohol. The aldehyde or ketone group is readily regenerated by hydrolysis using a large excess of water in the presence of acid. 15 For example, an amine group may be protected, for example, as an amide (-NRCO-R) or a urethane (-NRCO-OR), for example, as: a methyl amide (-NHCO-CH 3 ); a benzyloxy amide (-NHCO-OCH 2

C

6

H

5 , -NH-Cbz); as a t-butoxy amide (-NHCO-OC(CH 3

)

3 , -NH-Boc); a 2-biphenyl-2-propoxy amide (-NHCO-OC(CH 3

)

2

CH

4

C

6

H

5 , -NH-Bpoc), as a 9 20 fluorenylmethoxy amide (-NH-Fmoc), as a 6-nitroveratryloxy amide (-NH-Nvoc), as a 2-trimethylsilylethyloxy amide (-NH-Teoc), as a 2,2,2-trichloroethyloxy amide (-NH-Troc), as an allyloxy amide (-NH-Alloc), as a 2(-phenylsulphonyl)ethyloxy amide (-NH-Psec); or, in suitable cases (e.g., cyclic amines), as a nitroxide radical (>N-O). 25 For example, a carboxylic acid group may be protected as an ester for example, as: an

C

1

.

7 alkyl ester (e.g., a methyl ester; a t-butyl ester); a C 1

.

7 haloalkyl ester (e.g., a

C

1

.

7 trihaloalkyl ester); a triC 1

.

7 alkylsilyl-C 1

-

7 alkyl ester; or a C 5

.

20 aryl-C 1

.

7 alkyl ester (e.g., a benzyl ester; a nitrobenzyl ester); or as an amide, for example, as a methyl amide. 30 For example, a thiol group may be protected as a thioether (-SR), for example, as: a benzyl thioether; an acetamidomethyl ether (-S-CH 2

NHC(=O)CH

3

).

WO 2006/018649 PCT/GB2005/003242 14 Prodrugs It may be convenient or desirable to prepare, purify, and/or handle the active compound in the form of a prodrug. The term "prodrug," as used herein, pertains to a compound 5 which, when metabolised (e.g., in vivo), yields the desired active compound. Typically, the prodrug is inactive, or less active than the active compound, but may provide advantageous handling, administration, or metabolic properties. Unless otherwise specified, a reference to a particular compound also include prodrugs 10 thereof. For example, some prodrugs are esters of the active compound (e.g., a physiologically acceptable metabolically labile ester). During metabolism, the ester group (-C(=O)OR) is cleaved to yield the active drug. Such esters may be formed by esterification, for 15 example, of any of the carboxylic acid groups (-C(=O)OH) in the parent compound, with, where appropriate, prior protection of any other reactive groups present in the parent compound, followed by deprotection if required. Examples of such metabolically labile esters include those of the formula -C(=O)OR 20 wherein R is:

C

1 .yalkyl (e.g., -Me, -Et, -nPr, -iPr, -nBu, -sBu, -iBu, -tBu);

C

1 -yaminoalkyl (e.g., aminoethyl; 2-(N,N-diethylamino)ethyl; 2-(4-morpholino)ethyl); and 25 acyloxy-C 1

.

7 alkyl (e.g., acyloxymethyl; acyloxyethyl; pivaloyloxymethyl; acetoxymethyl; 30 1 -acetoxyethyl; 1 -(1 -methoxy-1 -methyl)ethyl-carbonxyloxyethyl; 1-(benzoyloxy)ethyl; isopropoxy-carbonyloxymethyl; 1-isopropoxy-carbonyloxyethyl; cyclohexyl-carbonyloxymethyl; 1 -cyclohexyl-carbonyloxyethyl; WO 2006/018649 PCT/GB2005/003242 15 cyclohexyloxy-carbonyloxymethyl; 1 -cyclohexyloxy-carbonyloxyethyl; (4-tetrahydropyranyloxy) carbonyloxymethyl; 1-(4-tetrahydropyranyloxy)carbonyloxyethyl; 5 ( 4 -tetrahydropyranyl)carbonyloxymethyl; and 1-( 4 -tetrahydropyranyl)carbonyloxyethyl). Also, some prodrugs are activated enzymatically to yield the active compound, or a compound which, upon further chemical reaction, yields the active compound (for 10 example, as in ADEPT, GDEPT, LIDEPT, etc.). For example, the prodrug may be a sugar derivative or other glycoside conjugate, or may be an amino acid ester derivative. Use of Compounds of the Invention The invention provides compounds of formula (I), or solvates or prodrugs thereof ("active 15 compounds"), for use in a method of treatment of the human or animal body. Such a method may comprise administering to such a subject a therapeutically-effective amount of an active compound, preferably in the form of a pharmaceutical composition. The term "treatment" as used herein in the context of treating a condition, pertains 20 generally to treatment and therapy, whether of a human or an animal (e.g. in veterinary applications), in which some desired therapeutic effect is achieved, for example, the inhibition of the progress of the condition, and includes a reduction in the rate of progress, a halt in the rate of progress, amelioration of the condition, and cure of the condition. Treatment as a prophylactic measure (i.e. prophylaxis) is also included. 25 The term "therapeutically-effective amount" as used herein, pertains to that amount of an active compound, or a material, composition or dosage form comprising an active compound, which is effective for producing some desired therapeutic effect, commensurate with a reasonable benefit/risk ratio. 30 Administration The active compound or pharmaceutical composition comprising the active compound may be administered to a subject by any convenient route of administration, whether systemically/ peripherally or at the site of desired action, including but not limited to, oral WO 2006/018649 PCT/GB2005/003242 16 (e.g. by ingestion); topical (including e.g. transdermal, intranasal, ocular, buccal, and sublingual); pulmonary (e.g. by inhalation or insufflation therapy using, e.g. an aerosol, e.g. through mouth or nose); rectal; vaginal; parenteral, for example, by injection, including subcutaneous, intradermal, intramuscular, intravenous, intraarterial, 5 intracardiac, intrathecal, intraspinal, intracapsular, subcapsular, intraorbital, intraperitoneal, intratracheal, subcuticular, intraarticular, subarachnoid, and intrasternal; by implant of a depot, for example, subcutaneously or intramuscularly. The subject may be a eukaryote, an animal, a vertebrate animal, a mammal, a rodent 10 (e.g. a guinea pig, a hamster, a rat, a mouse), murine (e.g. a mouse), canine (e.g. a dog), feline (e.g. a cat), equine (e.g. a horse), a primate, simian (e.g. a monkey or ape), a monkey (e.g. marmoset, baboon), an ape (e.g. gorilla, chimpanzee, orang-utan, gibbon), or a human. 15 Formulations While it is possible for the active compound to be administered alone, it is preferable to present it as a pharmaceutical composition (e.g. formulation) comprising at least one active compound, as defined above, together with one or more pharmaceutically acceptable carriers, adjuvants, excipients, diluents, fillers, buffers, stabilisers, 20 preservatives, lubricants, or other materials well known to those skilled in the art and optionally other therapeutic or prophylactic agents. Thus, the present invention further provides pharmaceutical compositions, as defined above, and methods of making a pharmaceutical composition comprising admixing at 25 least one active compound, as defined above, together with one or more pharmaceutically acceptable carriers, excipients, buffers, adjuvants, stabilisers, or other materials, as described herein. The term "pharmaceutically acceptable" as used herein pertains to compounds, 30 materials, compositions, and/or dosage forms which are, within the scope of sound medical judgement, suitable for use in contact with the tissues of a subject (e.g. human) without excessive toxicity, irritation, allergic response, or other problem or complication, commensurate with a reasonable benefit/risk ratio. Each carrier, excipient, etc. must WO 2006/018649 PCT/GB2005/003242 17 also be "acceptable" in the sense of being compatible with the other ingredients of the formulation. Suitable carriers, excipients, etc. can be found in standard pharmaceutical texts, for 5 example, Remington's Pharmaceutical Sciences, 18th edition, Mack Publishing Company, Easton, Pa., 1990. The formulations may conveniently be presented in unit dosage form and may be prepared by any methods well known in the art of pharmacy. Such methods include the 10 step of bringing into association the active compound with the carrier which constitutes one or more accessory ingredients. In general, the formulations are prepared by uniformly and intimately bringing into association the active compound with liquid carriers or finely divided solid carriers or both, and then if necessary shaping the product. 15 Formulations may be in the form of liquids, solutions, suspensions, emulsions, elixirs, syrups, tablets, losenges, granules, powders, capsules, cachets, pills, ampoules, suppositories, pessaries, ointments, gels, pastes, creams, sprays, mists, foams, lotions, oils, boluses, electuaries, or aerosols. 20 Formulations suitable for oral administration (e.g. by ingestion) may be presented as discrete units such as capsules, cachets or tablets, each containing a predetermined amount of the active compound; as a powder or granules; as a solution or suspension in an aqueous or non-aqueous liquid; or as an oil-in-water liquid emulsion or a water-in-oil liquid emulsion; as a bolus; as an electuary; or as a paste. 25 A tablet may be made by conventional means, e.g., compression or moulding, optionally with one or more accessory ingredients. Compressed tablets may be prepared by compressing in a suitable machine the active compound in a free-flowing form such as a powder or granules, optionally mixed with one or more binders (e.g. povidone, gelatin, 30 acacia, sorbitol, tragacanth, hydroxypropylmethyl cellulose); fillers or diluents (e.g. lactose, microcrystalline cellulose, calcium hydrogen phosphate); lubricants (e.g. magnesium stearate, talc, silica); disintegrants (e.g. sodium starch glycolate, cross linked povidone, cross-linked sodium carboxymethyl cellulose); surface-active or dispersing or wetting agents (e.g. sodium lauryl sulfate); and preservatives (e.g. methyl WO 2006/018649 PCT/GB2005/003242 18 p-hydroxybenzoate, propyl p-hydroxybenzoate, sorbic acid). Moulded tablets may be made by moulding in a suitable machine a mixture of the powdered compound moistened with an inert liquid diluent. The tablets may optionally be coated or scored and may be formulated so as to provide slow or controlled release of the active 5 compound therein using, for example, hydroxypropylmethyl cellulose in varying proportions to provide the desired release profile. Tablets may optionally be provided with an enteric coating, to provide release in parts of the gut other than the stomach. Formulations suitable for topical administration (e.g. transdermal, intranasal, ocular, 10 buccal, and sublingual) may be formulated as an ointment, cream, suspension, lotion, powder, solution, past, gel, spray, aerosol, or oil. Alternatively, a formulation may comprise a patch or a dressing such as a bandage or adhesive plaster impregnated with active compounds and optionally one or more excipients or diluents. 15 Formulations suitable for topical administration in the mouth include losenges comprising the active compound in a flavoured basis, usually sucrose and acacia or tragacanth; pastilles comprising the active compound in an inert basis such as gelatin and glycerin, or sucrose and acacia; and mouthwashes comprising the active compound in a suitable liquid carrier. 20 Formulations suitable for topical administration to the eye also include eye drops wherein the active compound is dissolved or suspended in a suitable carrier, especially an aqueous solvent for the active compound. 25 Formulations suitable for nasal administration, wherein the carrier is a solid, include a coarse powder having a particle size, for example, in the range of about 20 to about 500 microns which is administered in the manner in which snuff is taken, i.e. by rapid inhalation through the nasal passage from a container of the powder held close up to the nose. Suitable formulations wherein the carrier is a liquid for administration as, for 30 example, nasal spray, nasal drops, or by aerosol administration by nebuliser, include aqueous or oily solutions of the active compound. Formulations suitable for administration by inhalation include those presented as an aerosol spray from a pressurised pack, with the use of a suitable propellant, such as WO 2006/018649 PCT/GB2005/003242 19 dichlorodifluoromethane, trichlorofluoromethane, dichoro-tetrafluoroethane, carbon dioxide, or other suitable gases. Formulations suitable for topical administration via the skin include ointments, creams, 5 and emulsions. When formulated in an ointment, the active compound may optionally be employed with either a paraffinic or a water-miscible ointment base. Alternatively, the active compounds may be formulated in a cream with an oil-in-water cream base. If desired, the aqueous phase of the cream base may include, for example, at least about 30% w/w of a polyhydric alcohol, i.e., an alcohol having two or more hydroxyl groups 10 such as propylene glycol, butane-1,3-diol, mannitol, sorbitol, glycerol and polyethylene glycol and mixtures thereof. The topical formulations may desirably include a compound which enhances absorption or penetration of the active compound through the skin or other affected areas. Examples of such dermal penetration enhancers include dimethylsulfoxide and related analogues. 15 When formulated as a topical emulsion, the oily phase may optionally comprise merely an emulsifier (otherwise known as an emulgent), or it may comprises a mixture of at least one emulsifier with a fat or an oil or with both a fat and an oil. Preferably, a hydrophilic emulsifier is included together with a lipophilic emulsifier which acts as a stabiliser. It is 20 also preferred to include both an oil and a fat. Together, the emulsifier(s) with or without stabiliser(s) make up the so-called emulsifying wax, and the wax together with the oil and/or fat make up the so-called emulsifying ointment base which forms the oily dispersed phase of the cream formulations. 25 Suitable emulgents and emulsion stabilisers include Tween 60, Span 80, cetostearyl alcohol, myristyl alcohol, glyceryl monostearate and sodium lauryl sulphate. The choice of suitable oils or fats for the formulation is based on achieving the desired cosmetic properties, since the solubility of the active compound in most oils likely to be used in pharmaceutical emulsion formulations may be very low. Thus the cream should 30 preferably be a non-greasy, non-staining and washable product with suitable consistency to avoid leakage from tubes or other containers. Straight or branched chain, mono- or dibasic alkyl esters such as di-isoadipate, isocetyl stearate, propylene glycol diester of coconut fatty acids, isopropyl myristate, decyl oleate, isopropyl palmitate, butyl stearate, 2-ethylhexyl palmitate or a blend of branched chain esters known as Crodamol CAP may WO 2006/018649 PCT/GB2005/003242 20 be used, the last three being preferred esters. These may be used alone or in combination depending on the properties required. Alternatively, high melting point lipids such as white soft paraffin and/or liquid paraffin or 5 other mineral oils can be used. Formulations suitable for rectal administration may be presented as a suppository with a suitable base comprising, for example, cocoa butter or a salicylate. 10 Formulations suitable for vaginal administration may be presented as pessaries, tampons, creams, gels, pastes, foams or spray formulations containing in addition to the active compound, such carriers as are known in the art to be appropriate. Formulations suitable for parenteral administration (e.g. by injection, including 15 cutaneous, subcutaneous, intramuscular, intravenous and intradermal), include aqueous and non-aqueous isotonic, pyrogen-free, sterile injection solutions which may contain anti-oxidants, buffers, preservatives, stabilisers, bacteriostats, and solutes which render the formulation isotonic with the blood of the intended recipient; and aqueous and non aqueous sterile suspensions which may include suspending agents and thickening 20 agents, and liposomes or other microparticulate systems which are designed to target the compound to blood components or one or more organs. Examples of suitable isotonic vehicles for use in such formulations include Sodium Chloride Injection, Ringer's Solution, or Lactated Ringer's Injection. Typically, the concentration of the active compound in the solution is from about 1 ng/ml to about 10 pg/ml, for example from 25 about 10 ng/ml to about 1 pg/ml. The formulations may be presented in unit-dose or multi-dose sealed containers, for example, ampoules and vials, and may be stored in a freeze-dried (lyophilised) condition requiring only the addition of the sterile liquid carrier, for example water for injections, immediately prior to use. Extemporaneous injection solutions and suspensions may be prepared from sterile powders, granules, and tablets. 30 Formulations may be in the form of liposomes or other microparticulate systems which are designed to target the active compound to blood components or one or more organs.

WO 2006/018649 PCT/GB2005/003242 21 Dosage It will be appreciated that appropriate dosages of the active compounds, and compositions comprising the active compounds, can vary from patient to patient. Determining the optimal dosage will generally involve the balancing of the level of 5 therapeutic benefit against any risk or deleterious side effects of the treatments of the present invention. The selected dosage level will depend on a variety of factors including, but not limited to, the activity of the particular compound, the route of administration, the time of administration, the rate of excretion of the compound, the duration of the treatment, other drugs, compounds, and/or materials used in combination, 10 and the age, sex, weight, condition, general health, and prior medical history of the patient. The amount of compound and route of administration will ultimately be at the discretion of the physician, although generally the dosage will be to achieve local concentrations at the site of action which achieve the desired effect without causing substantial harmful or deleterious side-effects. 15 Administration in vivo can be effected in one dose, continuously or intermittently (e.g. in divided doses at appropriate intervals) throughout the course of treatment. Methods of determining the most effective means and dosage of administration are well known to those of skill in the art and will vary with the formulation used for therapy, the purpose of 20 the therapy, the target cell being treated, and the subject being treated. Single or multiple administrations can be carried out with the dose level and pattern being selected by the treating physician. In general, a suitable dose of the active compound is in the range of about 100 pg to 25 about 250 mg per kilogram body weight of the subject per day. Where the active compound is a salt, an ester, prodrug, or the like, the amount administered is calculated on the basis of the parent compound and so the actual weight to be used is increased proportionately. 30 Cancers Examples of cancers which may be treated by the active compounds include, but are not limited to, a carcinoma, for example a carcinoma of the bladder, breast, colon (e.g. colorectal carcinomas such as colon adenocarcinoma and colon adenoma), kidney, epidermal, liver, lung, for example adenocarcinoma, small cell lung cancer and non-small WO 2006/018649 PCT/GB2005/003242 22 cell lung carcinomas, oesophagus, gall bladder, ovary, pancreas e.g. exocrine pancreatic carcinoma, stomach, cervix, thyroid, prostate, or skin, for example squamous cell carcinoma; a hematopoietic tumour of lymphoid lineage, for example leukemia, acute lymphocytic leukemia, B-cell lymphoma, T-cell lymphoma, Hodgkin's lymphoma, non 5 Hodgkin's lymphoma, hairy cell lymphoma, or Burkett's lymphoma; a hematopoietic tumor of myeloid lineage, for example acute and chronic myelogenous leukemias, myelodysplastic syndrome, or promyelocytic leukemia; thyroid follicular cancer; a tumour of mesenchymal origin, for example fibrosarcoma or habdomyosarcoma; a tumor of the central or peripheral nervous system, for example astrocytoma, neuroblastoma, glioma 10 or schwannoma; melanoma; seminoma; teratocarcinoma; osteosarcoma; xenoderoma pigmentoum; keratoctanthoma; thyroid follicular cancer; or Kaposi's sarcoma. Examples of other therapeutic agents that may be administered together (whether concurrently or at different time intervals) with the compounds of the formula (1) include 15 but are not limited to topoisomerase inhibitors, alkylating agents, antimetabolites, DNA binders and microtubule inhibitors (tubulin target agents), such as cisplatin, cyclophosphamide, doxorubicin, irinotecan, fludarabine, 5FU, taxanes, mitomycin C or radiotherapy. For the case of active compounds combined with other therapies the two or more treatments may be given in individually varying dose schedules and via different 20 routes. The combination of the agents listed above with a compound of the present invention would be at the discretion of the physician who would select dosages using his common general knowledge and dosing regimens known to a skilled practitioner. 25 Where the compound of the formula (1) is administered in combination therapy with one, two, three, four or more, preferably one or two, preferably one other therapeutic agents, the compounds can be administered simultaneously or sequentially. When administered sequentially, they can be administered at closely spaced intervals (for example over a 30 period of 5-10 minutes) or at longer intervals (for example 1, 2, 3, 4 or more hours apart, or even longer periods apart where required), the precise dosage regimen being commensurate with the properties of the therapeutic agent(s).

WO 2006/018649 PCT/GB2005/003242 23 The compounds of the invention may also be administered in conjunction with non chemotherapeutic treatments such as radiotherapy, photodynamic therapy, gene therapy; surgery and controlled diets. 5 Preferences

R

1

-R

6 In one group of embodiments of the present invention, R' and R 2 together with the ring to which they are attached form a saturated or unsaturated carbocyclic or heterocyclic group containing up to 3- to 8- membered carbocyclic or heterocyclic rings, wherein each 10 carbocyclic or heterocyclic ring may be fused to one or more other carbocyclic or heterocyclic rings. In this group of embodiments, it is preferred that R 3 , R 4 , R 5 and R 6 are H. 15 R 1 and R 2 together with the ring to which they are bound in compounds of formula (I) may represent an ortho- or peri-fused carbocyclic or heterocyclic ring system.

R

1 and R 2 together with the ring to which they are bound may represent a wholly carbocyclic fused ring system such as a ring system containing 2 or 3 fused carbocyclic 20 rings, e.g. optionally substituted, optionally hydrogenated naphthalene or anthracene. Alternatively, R 1 and R 2 together with the ring to which they are bound in compounds of formula (I) may represent a fused tricyclic ring such as anthracene or a mono, di, tri, tetra or higher hydrogenated derivative of anthracene. For example, R1 and R 2 together with 25 the ring to which they are bound in formula (1) may represent anthracene, 1, 4 dihydroanthracene or 1, 4, 9, 10-tetrahydroanthracene.

R

1 and R 2 together with the ring to which they are bound in formula (I) may also represent: WO 2006/018649 PCT/GB2005/003242 24 coIIDQ 9 -8 oor In another group of embodiments, R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are independently selected from H, C 1

.

7 alkyl, C5-2o aryl, C3- 2 0 heterocyclyl, halo, ester, amido, acyl, sulfo, 5 sulfonamido, ether, thioether, azo and amino. In this group of embodiments, R', R 2 , R 3 ,

R

4 , R 5 and R 6 are preferably independently selected from H, C1-7 alkyl, C 5

-

2 0 aryl and ester. Of these H and C1-7 alkyl (in particular C1.3 alkyl)are most preferred. In this group of embodiments, four, five or six of R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are preferably 10 hydrogen, with the other (if any) groups being selected from C 1

-

7 alkyl, Cs-20 aryl, C 3

-

20 heterocyclyl, halo, ester, amido, acyl, sulfo, sulfonamido, ether, thioether, azo and amino, or more preferably CI. alkyl, C9-20 aryl and ester, and most preferably C 1

.

7 alkyl (in particular C1-3 alkyl). If two of R 1 , R 2 , R 3 , R 4 , R 5 and R 6 are not H, then these groups are preferably meta or para to one another, and more preferably para to one another. 15 Examples of particularly preferred substitutent patterns include, but are not limited to: phenyl; 1-methyl; and 4-iso-propyl. A and B 20 It is preferred that A and B together represent NRN 4 RN5-(CRc1R 2 )n-NRN6RN7, wherein Rc and RC 2 are independently selected from H and C1.4 alkyl, RN 4 , RN5, RN' and RN 7 are independently selected from H and C1.4 alkyl, and n is an integer from 1 to 4. Preferably, R 1 4 and R 1 5 are both hydrogen. Preferably n is 2 or 3, more preferably 2. 25 RN 4 , RN5, RN6 and RN 7 are preferably H or methyl and, more preferably, all of RN 4 , RN5 RN6 and RN 7 are H.

WO 2006/018649 PCT/GB2005/003242 25 When RN 4 is present in A, then p is 0. When RN 4 is absent, then p is I and C' takes the place of RN 4 . In a group of embodiments, RN 4 is absent from A, p is I and preferably C' is

C

4

.

10 alkylene with no substituents (e.g. hexylene). 5 Examples of dinuclear complexes of this group of embodiments are those in which pairs of A and B together with linker C' represent:

H

2 N NH-(CH 2

)

6 -HN NH 2

H

2 N NH NH NH2 H2N CH2 NH2 H 2 N NH-(CH 2 )x(NH)(CH 2 )x--HN NH 2 H2N NH 2

H

2 N NH-(CH 2 )x(NH)(CH 2 )y(NH)(CH2). -HN NH 2

(CH

2 )n H2N NH2 H2N NH2 H 2 N NH-(CH 2 )x(CONH)(CH2)y(NHOC)(CH 2 )x--HN NH 2 0 (CH 2 ). a

H

2 N NH-C-(CH 2

)

4 C-NH NH 2 -0 NH 2

H

2 N a O (CH 2 )-HN0C-F3\---C0NH-(H 2 )n 0

H

2 N NH-(CH 2 )s-HN NH 2 -0 NH 2

H

2 N a.. wherein each n', n", x', x" and y' independently represents an integer from 1 to 12, preferably 1 to 6. 10 X When X is an N-donor ligand, it is preferably selected from azide, isothiocyanate, and optionally substituted pyridine ligands. Of these, azide and isothiocyanate are preferred. 15 When X is an optionally substituted pyridine ligand, the ligand is preferably at least mono-substituted, and may be di-substituted. These substituents are preferably selected from halo (e.g. chloro, flouro), cyano, and lower alkyl (e.g. methyl). Of these, chloro, WO 2006/018649 PCT/GB2005/003242 26 cyano and methyl are preferred. Preferred substituent patterns include, but are not limited to, 3-, 5-dichloro, 4-cyano and 3-methyl. In some embodiments, X is selected from nitrile ligands (NEC-R); azo ligands (N=N-R); 5 amine ligands (N RN1RN 2

RN

3 ); azide (N 3 ~); cyanide (NEC~) and isothiocyanate (NCS~). If X is an S-donor ligand, it is preferably a thiolate ligand, for example, PhS-. yq 10 yq- in compounds of formula (I) is a counterion and is only present in the compound when the complex containing the metal ion is charged. yq- is preferably a non nucleophilic anion such as PF 6 ~, BF 4 , BPh 4 --or CF 3 0 2 SO- ,for example. General Synthesis Methods 15 The present invention also provides a process for preparing the compounds of the invention which comprises the reaction of a compound of formula [(rn 6 C 6 (Rl)(R 2

)(R

3

)(R

4

)(R)(R

6 ))RuABC][Yq], which may be in the form of a monomer or a dimer, with AgNO 3 in a suitable solvent for the reaction, followed by removal of AgCI and reaction with MX, optionally in the presence, or with subsequent addition of, yq-, in a 20 suitable solvent for the reaction, wherein R', R 2 , R 3 , R 4 , R , R , X, A, B and Y are as defined above for the compounds of the invention, and M is an appropriate cation, e.g. Na*. Preferred reaction conditions include: 25 (a) stirring the starting ruthenium complex, as described above, in a 1:1 mixture of MeOH and H 2 0 as a solvent with AgNO 3 ; (b) filtering off the AgCl precipitate formed; (c) adding MX (which may be dissolved by heating, if necessary) and allowing to react; 30 (d) adding a source of yq-, such as a compound of formula (NH 4 *)Yq, e.g., NH 4

PF

6 , and evaporating the filtrate to yield the product. The filtrate may be purified, for example, by recrystalisation from acetone.

WO 2006/018649 PCT/GB2005/003242 27 The following non-limiting examples illustrate the present invention. Examples General Methods 5 Electrospray lonisation Mass Spectrometry (ESI-MS): Positive-ion electrospray ionisation mass spectra were obtained with a Platform I mass spectrometer (Micromass, Manchester, U.K.). For offline ESI-MS assays, the samples were prepared in 50%

CH

3 CN / 50% H 2 0 (v/v) and infused directly into the mass spectrometer at 6 [LL min-. The ions were produced in an atmospheric pressure ionisation (API) / ESI ion source. 10 For the online LC-ESI-MS assays, a Waters 2690 HPLC system was interfaced with the mass spectrometer, using the same column and gradients as described above for the HPLC assays with a flow rate of 1.0 mL min- and a splitting ratio of 1/5. The spray voltage was 3.50-3.68 kV. The cone voltage was varied over the range of 15-30 V as required. The capillary temperature was 338 K for direct infusion and 413 K for the HPLC 15 sampling, with a 450 L W flow of nitrogen drying gas. The quadrupole analyser, operated at a background pressure of 2 x 10-5 Torr, was scanned at 300 Da s- for direct infusion and 750 Da s- for HPLC sampling. Data were collected (for 10 scans during the direct infusion assays) and analysed on a Mass Lynx (ver. 2.3) Windows NT PC data system using the Max Ent Electrospray software algorithm and calibrated versus an Nal 20 calibration file. The mass accuracy of all measurements was within 0.1 m/z unit. X-ray crystallography: All data were collected at 150 K on a Bruker Smart Apex CCD diffractometer equipped with an Oxford Cryosystems low-temperature device. Following application of a multi-scan absorption correction (SADABS)(Sheldrick, G.M., SADABS, 25 Program for carrying-out multiscan absorption corrections, University of Gttingen, Germany, 1998) the structures were all solved by direct methods (Shelxs, SIR92, Dirdif) (Sheldrick, G.M., SHELXS and SHELXL. Programs for the solution and refinement of crystal structures, University of G6ttingen, Germany, 1998; Altomare, A., et a., A. J. App. Crystallogr., 26, 343-350 (1993); Beurskens, P.T., et al., The DIRDIF96 Program 30 System, Technical Report of the Crystallography Laboratory, University of Nijmegen, The Netherlands (1996)) and refined against F 2 using all data (SHELXL) (Betteridge, P.W., et al., J. Apple. Cryst., 36, 1487 (2003)) WO 2006/018649 PCT/GB2005/003242 28 Comparative Example 1: Synthesis of [(N 6

-C

6

H

5

C

6

H

5 )Ru(en)Cl][PF 6 ] (Cl)

PF

6 H N /Ru'Cl

<,NH

2 This compound was synthesised as described in Morris, R.E., et al., J. Med. Chem., 44, 3616-3621 (2001) - compound 9. 5 Example 1: Synthesis of [(n 6

-C

6

H

5

C

6 Hs)Ru(en)N 3

][PF

6 ] (1) PF

H

2 N RuN

NH

2 N This complex was prepared by refluxing complex C1 (25.0 mg, 0.0496 mmol) and AgNO 3 (8.4 mg, 0.0494 mmol) in 2.5 mL of a 1:1 mixture of MeOH and H 2 0 for one hour. AgCl 10 was removed by filtration. NaN 3 was added (163 mg, 2.51 mmol), dissolved by heating, and left overnight. NH 4 PF6 (250 mg) was added, leading to a microcrystalline, yellow precipitate. Recrystallization of the precipitate from acetone gave a yellow crystalline product. Yield of 1: 8.6 mg (34%). Anal. Calcd for C 1 4

F

6

H

18 NsPRu: C 33.47, H 3.61, N 13.94. Found: C 33.37, H 3.46, N 15 13.68. MS: m/z 357,7 for [M-PF 6 ]* (calc. 357.1) Comparative Example 2: Synthesis of [( 1 6

-C

6

(CH

3 ))Ru(en)Cl][PF 6 ] (C2) Me PF 6 Me Me Me Me _RMe H2 R'cl This complex was prepared in an analogous manner to compound C1 in Comparative 20 Example 1 from [(" 6

-C

6

(CH

3

)

6 )RuC21 2 . Yield of C2: 68%. Anal. Calcd. for

C

1 4

F

6

H

1 2

N

2 CIPRu : C 33.59, H 4.43, N 5.60 Found: C 33.55, H 4.57, N 5.54 WO 2006/018649 PCT/GB2005/003242 29 Example 2: Synthesis of [(r]-C(CH 3 ))Ru(en)(pyridine)][PF 6

]

2 (2) Me (PF 6

)

2 Me Me Me Me -Ru Me

H

2 N R ZNH2L This complex was prepared by refluxing complex C2 (25.0 mg, 0.0496 mmol) and AgNO 3 (8.4 mg, 0.0494 mmol) in 2.5 mL of a 1:1 mixture of MeOH and H 2 0 for one hour. AgCl 5 was removed by filtration. Pyridine (101 p, 1.25 mmol) was added and the mixture was left overnight. The volume was reduced to ca. 1.5 mL by rotary evaporation and 100 mg of NH 4 PF6 was added. The yellow precipitate was dissolved in acetone. The solution was then filtered and the acetone allowed to evaporate slowly, resulting in a microcrystalline, yellow product. Yield of 2: 19.3 mg (56%). Anal. Calcd for 10 C 19

F

12

H

31

N

3

P

2 Ru: C 32.96, H 4.51, N 6.07. Found: C 33.47, H 4.50, N 6.24. Example 3: Synthesis of [(g 6

-C

6

(CH

3 ))Ru(en)(SCN)][PF] 2 (3) Me PF, Me Me Me Me H2N Ru Me

Z_,NH

2 11 C S This complex was prepared by refluxing complex C2 (25.0 mg, 0.0496 mmol) and AgNO 3 15 (7.0 mg, 0.0412 mmol) in 2.5 mL of a 1:1 mixture of MeOH and H 2 0 for one hour. AgCl was removed by filtration. KSCN was added (243 mg, 2.50 mmol) and the solution stirred for one day. 150 mg of KPF 6 was added, and enough acetone was added to dissolve the resulting precipitate. Slow evaporation of the acetone yielded yellow crystals, which were suitable for X-ray crystallography studies. Yield: 6.9 mg (26 %) 20 X-ray crystal structure determination yielded the result shown below, from which it can be seen that the isothiocyanate is bound via the nitrogen atom. Crystal data and structure refinement for compound 3 25 X-ray data: WO 2006/018649 PCT/GB2005/003242 30 Crystal Data Empirical formula C15 H26 F6 N3 0 P Ru S Formula weight 542.49 Crystal system Orthorhombic 5 Space group Pca2l Unit cell dimensions a = 14.7411(12)A a = 90 deg. b = 9.0154(7)A p 90 deg. c = 15.6070(12)A y 90 deg. Volume 2074.1(3)A 3 10 Z 4 Data Collection Instrument Bruker Smart Apex CCD 15 Solution and Refinement Solution Patterson (Dirdif) R1 0.0619 [5064 data] SiM N11E N(2E) 2012E 20 WO 2006/018649 PCT/GB2005/003242 31 Example 4: Synthesis of [(,9 6

-C(CH

3 ))Ru(en)(SPh)][PF 6 ] (4) Me PF, Me e Me Me Ru ,Me

NH

2 This complex was prepared by refluxing complex C2 (25.0 mg, 0.0496 mmol) and AgNO 3 (8.4 mg, 0.0494 mmol) in 2.5 mL of a 1:1 mixture of MeOH and H 2 0 for one hour. AgCl 5 was removed by filtration. NaSPh was added (7.9 mg, 0.0595 mmol) and the solution was left overnight. 250 mg of NH 4

PF

6 was added, leading to an orange precipitate. Slow evaporation of the acetone solution of the precipitate led to a crystalline orange product and a yellow powder, both of which, by mass spectrometry, seemed to be the desired compound. Yield: 10.2 mg (36 %). MS: m/z 433.0 for [M - PF 6 ]* (CaIc. 433.1). 10 Example 5: Synthesis of [(T 6

-C

6

(CH

3

)

6 )Ru (en)N 3

][PF

6 ] (5) Me Me PFe MeM Me H2N Ru Me 2N NH 2 11 N This complex was prepared by refluxing complex C2 (25.0 mg, 0.0496 mmol) and AgNO 3 (8.4 mg, 0.0494 mmol) in 2.5 mL of a 1:1 mixture of MeOH and H 2 0 for one hour. AgCl 15 was removed by filtration. NaN 3 was added (163 mg, 2.51 mmol), dissolved by heating, and left overnight. NH 4 PFe (250 mg) was added, leading to a microcrystalline, yellow precipitate. Recrystallization of the precipitate from acetone gave to a yellow crystalline product. Yield of 5: 16.4 mg (65%). Anal. Calcd for C 14

F

6

H

26

N

5 PRu: C 32.94, H 5.13, N 13.72. Found: C 32.32, H 4.45, N 12.63. 20 WO 2006/018649 PCT/GB2005/003242 32 Example 6: Synthesis of [(1 6

-C

6

(CH

3 ))Ru(en)(3,5-dichloropyridine)][PF 6

]

2 (6) Me - (PF 6

)

2 Me Me Me Me RuMe H2 2' N cl N I ci This complex was prepared in an analogous manner to compound 2 in Example 2. MS: m/z 616.0 for [6 - PF 6 ]* (Calc. 616.0) 5 Example 7: Synthesis of [(1 6

-C(CH

3 ))Ru(en)(3,5-difluoropyridine)][PF] 2 (7) Me 7 PF 6 Me Me Me Me H N RuMe H2 H H2 N 11 F F This complex was prepared in an analogous manner to compound 2 in Example 2. MS: m/z 583.9 for [7 - PF 6 ]* (Calc. 584.1) 10 Example 8: Synthesis of [(T 6

-C

6

(CH

3 ))Ru(en)(p-cyanopyridine)][PF] 2 (8) Me ] PF 6 Me Me Me Me RuMe H NH2 N N CN This complex was prepared in an analogous manner to compound 2 in Example 2. MS: m/z 572.9 for [8 - PF 6 ]* (Calc. 573.1) 15 X-ray data: Crystal Data Empirical formula C20 H30 F12 N4 P2 Ru Formula weight 717.49 WO 2006/018649 PCT/GB2005/003242 33 Crystal system Monoclinic Space group P2(1)/n Unit cell dimensions a = 8.6230(2)A a = 900 b = 34.7990(10)A p = 114.4360(10)0 5 c = 9.8620(3)A y 90 Volume 2694.22(13) A 3 Z 4 Data Collection Absorption correction SADABS 10 Solution and Refinement Solution direct (SHELXS-97) Program used for refinement SHELXL-97 R1 0.0575 [4950 data] 15 NIN N2 N4) Example 9: Synthesis of [(7 1 6

-C(CH

3 ))Ru(en)(3-methylpyridine)][PF] 2 (9) Me ] PF 6 Me Me Me Ru Me H2 -- 4 u ,,Me NH N Me 20 This complex was prepared in an analogous manner to compound 2 in Example 2. MS: m/z 562.1 for [9 - PF 6 ]* (Calc. 562.1) WO 2006/018649 PCT/GB2005/003242 34 X-ray data: Crystal Data Empirical formula C20 H27 F12 N3 P2 Rul Formula weight 700.45 5 Crystal system Orthorhombic Space group P n a 21 Unit cell dimensions a = 21.3199(6)A a = 90* b = 7.7155(2)A p = 9 0 c = 16.1809(5)A y 90* 10 Volume 2661.66 A 3 Z 4 Data Collection Absorption correction SADABS 15 Solution and Refinement Solution direct (SHELXS-97) Program used for refinement SHELXL-97 R1 = 0.0444 20 Ru SNI , N N7 Ci WO 2006/018649 PCT/GB2005/003242 35 Example 10: Analysis of Compounds Methods Ultraviolet and Visible (UV-Vis) Spectroscopy: A Perkin-Elmer Lambda-1 6 UV-Vis spectrophotometer was used with 1-cm path-length quartz cuvettes (0.5 mL) and a PTP1 5 Peltier temperature controller. Spectra were processed using UVWinlab software for Windows' 95. Kinetic Studies: Aliquots of stock solutions of the complexes to be tested (4 - 10 mM) in methanol were diluted to 500 [tL with water, and the absorbance at selected wavelengths 10 (determined by hydrolysis in an 19:1 mixture of water and methanol - see table 1 (A)) was then recorded at 6 to 20 second intervals depending on the hydrolysis rate of each complex at 298 K. The hydrolysis rate constant kH20 for each complex was determined by computer fit of the absorbance/time data for each complex to the first-order rate equation (eq.1), 15 A = Co + C 1 e M (1) where Co and C1 are computer-fitted constants, and A is the absorbance corresponding to time t, and the results are reported in table 1 as the half life (ty). Cytoxicity Studies 20 A2780 ( 1 st Method): A2780 cells were plated on day zero, and the complexes to be tested were added on day 3. The complex was removed on day 4 (i.e., 24 h cell exposure), and after growth in fresh medium in the absence of drug, the cells were counted on day 7. The complexes were stored in the dark at 277 K as a precaution against photochemical decomposition. The IC 50 (dose of compound required to cause 25 50% inhibition of cell growth) values are listed in Table 1. A2780 ( 2 nd method) and A549: Cell line A2780 (human ovarian carcinoma, ECACC 93112519) was maintained in medium comprising RPMI-1 640 (Sigma) with 5% Fetal 30 Bovine Serum (Invitrogen), 2mM L-Glutamine (Sigma) and 1% Penicillin / Streptomycin (Invitrogen), in T-75 flasks (Costar). Cells were passaged at approximately 75-90% confluence (1:8 dilution) using 0.25% Trypsin / EDTA (Invitrogen) WO 2006/018649 PCT/GB2005/003242 36 Cell Line A549 (human lung carcinoma, ECACC 86012804) was maintained in medium comprising DMEM (Sigma) with 10% Fetal Bovine Serum (Invitrogen), 2mM L-Glutamine (Invitrogen) and 1% Penicillin / Streptomycin (Invitrogen), in T-75 flasks (Costar). Cells were passaged at approximately 70-90% confluence (1:8 dilution) using 0.25% Trypsin / 5 EDTA (Invitrogen). Both cell lines were incubated at 37)C, 5% C0 2 , in high humidity. A2780 carcinoma cells were seeded (150pL) into 96 well plates (Nunc Maxisorp) at 5000 10 (± 10%) cells per well and incubated at 37 0 C, 5% CO 2 in high humidity for 48 hours. A549 carcinoma cells were seeded (150pL) into 96 well plates (Nunc Maxisorp) at 2000 (± 10%) cells per well and incubated at 37 0 C, 5% CO 2 in high humidity for 24 hours. The compounds to be tested were solubilised by sonication in DMSO (Fisher Scientific) 15 to provide 20mM solutions. Compounds were serially diluted with DMSO before diluting in cell culture medium to give concentrations four-fold greater than the final concentrations required in the assay. The dilutions of compound in culture medium were added to the cell plates (50pL) in triplicates to achieve final concentrations of 100pM, 50pM, 10pM, 5pM, 1pM and 0.1pM. The final DMSO concentration in each well was 20 0.5% (v/v). The plates were incubated for 24 hours at 37 0 C, 5% CO 2 , in high humidity. After 24 hours incubation, the cells were washed (200pL) twice with sterile phosphate buffered Saline (Sigma) and the cell culture medium replenished (200pL). Plates were incubated at 37 0 C, 5% C0 2 , in high humidity for 96 hours. After the incubation surviving 25 cells were fixed by the addition of 50%(w/v) Trichloroacetic acid (50pL) and incubated at 4 0 C for 1 hour. Plates were washed three times with excess tap water and air-dried. Cells were dyed by the addition of (1 OOpL) 0.4% sulforhodamine B (Sigma) solution to the plates followed by five washes (200pl) with 1 % acetic acid solution to remove excess 30 dye before air-drying. Dye was re-solubilised in (200pL) 10mM Tris buffer (Fisher Scientific) and the absorbance of each well read at both 565nm and 690nm using a BMG Fluorostar microplate reader. The reading at 690nm was subtracted from the 565nm reading, and the IC 5 0 values determined by plotting the corrected absorbance value Vs.

WO 2006/018649 PCT/GB2005/003242 37 the compound concentration in the wells (XLfit version 4.0, ID Business Solutions Ltd). These are shown below in table 1 Results 5 The results of the above analyses are shown in table 1 below. Table 1

IC

5 0 (pM) Compound A (nm) ty. (min) A2780 A2780 A549

(

1 st method) ( 2 "ld method) C1 260 5.0 8 6.5 11 1 270 367 4 14 8.5 C2 254 0.44 9 2 -a -a 3 24 4 -a -a 23 23 38 5 270 21.3 18 7.9 6 270 537 23 18 7 270 555 8 270 43.9 6 9 254 -a 50 50 a- no hydrolysis observed by UV-VIS

Claims (16)

1. A ruthenium (11) compound of formula (1): R R+ Ru x RuA-(C'), B r (I) or a solvate or prodrug thereof, wherein: 5 R', R

2 , R 3 , R 4 , R 5 and R 6 are independently selected from H, C1.7 alkyl, C 5 - 2 0 aryl, C 3 - 2 0 heterocyclyl, halo, ester, amido, acyl, sulfo, sulfonamido, ether, thioether, azo, amino, or R1 and R 2 together with the ring to which they are attached form a saturated or unsaturated carbocyclic or heterocyclic group containing up to three 3- to 8- membered carbocyclic or heterocyclic rings, wherein each carbocyclic or heterocyclic ring may be 10 fused to one or more other carbocyclic or heterocyclic rings; X is a neutral or negatively charged N- or S- donor ligand; Y is a counterion; m is 0 or 1; q is 1, 2 or 3; 15 C' is C 1 . 1 2 alkylene bound to two A groups; p isO or 1 and r is I when p is 0and r is 2 when p is 1; and A and B are each independently 0-donor, N-donor or S-donor ligands, and may be connected to one another. 20 2. A compound according to claim 1, wherein X is selected from azide, isothiocyanate, and optionally substituted pyridine ligands.

3. A compound according to claim 1, wherein X is a thiolate ligand. 25

4. A compound according to any one of claims 1 to 3, wherein A and B together represent NRN 4 RN 5 _(CRC1RC 2 )n-NRN6RN 7 , wherein Rc1 and RC 2 are independently selected WO 2006/018649 PCT/GB2005/003242 39 from H and C 1 4 alkyl, RN 4 , RN 5 , RN 6 and RN 7 are independently selected from H and C 1 4 alkyl, and n is an integer from 1 to 4.

5. A compound according to claim 4, wherein R 14 and R1 5 are both hydrogen. 5

6. A compound according to either claim 4 or claim 5, wherein n is 2.

7. A compound according to any one of claims 4 to 6, wherein RN 4 , RN5, RN6 and RN 7 are H. 10

8. A compound according to any one of claims 1 to 7, wherein R' and R 2 together with the ring to which they are attached form a saturated or unsaturated carbocyclic or heterocyclic group containing up to 3- to 8- membered carbocyclic or heterocyclic rings, wherein each carbocyclic or heterocyclic ring may be fused to one or more other 15 carbocyclic or heterocyclic rings.

9. A compound according to claim 8, wherein R 3 , R 4 , R 5 and R 6 are H.

10. A compound according to any one of claims 1 to 7, wherein R 1 , R 2 , R 3 , R 4 , R 5 and 20 R 6 are independently selected from C 1 . 7 alkyl, C5-20 aryl, C 3 - 20 heterocyclyl, halo, ester, amido, acyl, sulfo, sulfonamido, ether, thioether, azo and amino.

11. A compound according to claim 10, wherein R', R 2 , R', R 4 , R 5 and R 6 are independently selected from H and C 1 . 7 alkyl. 25

12. A compound according to either claim 10 or claim 11, wherein at least four of RI, R 2 , R 3 , R 4 , R 5 and R 6 are hydrogen.

13. A composition comprising a compound according to any one of claims 1 to 12, 30 and a pharmaceutically acceptable carrier or diluent.

14. The use of a compound according to any one of claims 1 to 12 in a method of therapy. WO 2006/018649 PCT/GB2005/003242 40

15. The use of a compound according to any one of claims 1 to 12 in the preparation of a medicament for the treatment of cancer.

16. A method of treatment of a subject suffering from cancer, comprising 5 administering to such a subject a therapeutically-effective amount of a compound according to any one of claims 1 to 12.