This invention relates to indolyl-pyridone derivatives having checkpoint kinase 1 (CHK1) inhibitory activity, to the use of such compounds in medicine, particularly in relation to the treatment of cancer, via the inhibition of aberrant cell proliferation, and to pharmaceutical compositions containing such compounds.

Background of the invention

Many standard cancer chemotherapeutic agents act primarily through their ability to induce DNA damage causing tumor growth inhibition. However, these agents cause cell cycle arrest by induction of checkpoints at either S-phase or G2-M boundary. The G2 arrest allows the cell time to repair the damaged DNA before entering mitosis. CHK1 and an unrelated serine/threonine kinase, CHK2, play a central role in arresting the cell cycle at the G2-M boundary (O'Connell et al EMBO J (1997) vol 16 P545-554). CHK1/2 induce this checkpoint by phosphorylating serine 216 of the CDC25 phosphatase, inhibiting the removal of two inactivating phosphates on cyclin dependent kinases (CDKs) (Zheng et al Nature (1998) vol 395 p507-510). Another overlapping pathway mediated by p53 also elicits cycle arrest in response to DNA- damage. However, p53 is mutationally inactivated in many cancers, resulting in a partial deficiency in their ability to initiate a DNA-repair response. If CHK1 activity is also inhibited in p53-negative cancers, all ability to arrest and repair DNA in response to DNA-damage is removed resulting in mitotic catastrophe and enhancing the effect of the DNA damaging agents (Konarias et al Oncogene (2001) vol 20 p7453-7463, Bunch and Eastman Clin. Can. Res. (1996) vol 2 p791-797, Tenzer and Pruschy Curr. Med Chem (2003) vol 3 p35-46). In contrast, normal cells would be relatively unaffected due to retention of a competent p53-mediated cell-cycle arrest pathway. The inhibition of DNA damage checkpoints is therefore expected to sensitise aberrantly proliferating cells to DNA damaging agents. Such sensitization is in turn expected to increase the therapeutic index of such chemotherapeutic agents or ionizing radiation. (Clary, D.O. Inhibition of Chk kinases in a leukemia model abrogates DNA damage checkpoints and promotes mitotic catastrophe. Proc Am Assoc Cancer Res (AACR) 2007, 48: Abst 5385) Therefore it is expected that efficacious inhibitors of CHK1 will lead to a corresponding Improvement in the efficacy of current DNA-damage inducing chemotherapeutic regimens (Sausville et al, J. Clinical Oncology (2001) vol19 p2319-2333). A number of putative CHK1 inhibitors are currently in phase I clinical trials including SCH900776 (Phase I dose escalation study with and without gemcitabine in patients with solid tumours or lymphoma), PF 00477736 (Phase I Study of PF-00477736 with gemcitabine in patients with advanced solid malignancies) & AZD7762 (Phase I open label multi centre dose escalation study to assess safety tolerability and pharmacokinetics of AZD7762 administered as a single intravenous agent and in combo with weekly standard dose gemcitabine in patients with advanced solid malignancies). Thus, there remains an unmet medical need for low molecular weight CHK1 inhibitors with pharmacokinetic and pharmacodynamic properties making them suitable for use as pharmaceutical agents. The object of the present invention is to provide such pharmaceutical agents and treatments.

It has now been found that certain indolyl-pyridone derivatives show efficacy as CHK1 inhibitors.

Brief description of the invention

The present invention relates to a class of substituted indolyl-pyridone compounds useful as CHK1 inhibitors, for example, for the treatment of cancer. A core indolyl- pyridone template, with substitution on the pyridone portion by a substituted-pyrazolyl amido-linked group are principle characterising features of the compounds with which the invention is concerned.

Detailed description of the invention

According to the present invention, there is provided a compound of formula (I) or a pharmaceutically acceptable salt thereof:

wherein R ₁ , R ₂ , R ₅ and R ₆ are independently selected from hydrogen, hydroxy, methyl, trifluoromethyl, hydroxy methyl, methoxy, trifluoromethoxy, methylamino and dimethylamino;

R ₃ and R ₄ , are independently selected from hydrogen, hydroxy, C ₁ -C ₃ alkyl, fluoro- (C _r C ₃ )-alkyl, hydroxy-(C _r C ₃ )-alkyl, C ₁ -C ₃ alkoxy, fluoro-Cd-CsJ-alkoxy, hydroxy-CC^ C ₃ )-alkoxy, -N(Rn)-R ₁₂ , -AIk-N(Rn)-R ₁₂ , -0-AIk-N(Rn)-R ₁₂ , -C(=O)OH, carboxy-(C _r C ₃ )-alkyl, or -C(=O)-NH-R ₁₃ ;

AIk is a straight or branched chain divalent C ₁ -C ₆ alkylene radical;

R ₇ and R ₈ are independently selected from hydrogen, hydroxy, or C ₁ -C ₃ alkoxy;

X is a straight chain divalent C ₁ -C ₃ alkylene radical, optionally substituted on one or more carbons by R ₉ and/or R ₁₀ ;

R ₉ and R ₁₀ are independently selected from methyl, hydroxy, or fluoro; R ₁₁ is hydrogen, C ₁ -C ₃ alkyl, or fluoro-(C _r C ₃ )-alkyl, and

R ₁₂ is C ₁ -C ₃ alkyl or hydroxy^d-CeJ-alkyl, either of which may be optionally substituted on the alkyl portion by phenyl, C ₁ -C ₃ alkoxy-(C _r C ₃ )-alkyl, 1IaIo-(C ₁ -C ₄ )- alkyl, C ₃ -C ₆ cycloalkyl, methylsulfonyl-(C ₁ -C ₃ )-alkyl or -N(R ₁₈ )-R ₁₉ ;

R ₁₃ is hydrogen, C ₁ -C ₃ alkyl, fluoro-(C ₁ -C ₃ )-alkyl, or a radical of formula -AIk-N(R ₁₄ )-

R ₁₄ and R _1S are independently selected from hydrogen, C ₁ -C ₃ alkyl, or f IuOrO-(C ₁ -C ₃ )- alkyl; or R ₁₁ and R ₁₂ , or R ₁₄ and R ₁₅ , together with the nitrogen atom to which they are respectively attached, form an optionally substituted, 4- to 6-membered, monocyclic heterocyclic ring having no more than three additional heteroatoms independently selected from oxygen, sulphur and nitrogen;

W is selected from -C(=0)-N(-R ₁₆ )- or-N(-R ₁₇ )-C(=O)-; R ₁₆ or R ₁₇ is selected from hydrogen, C ₁ -C ₃ alkyl, or fluoro-(CrC ₃ )-alkyl;

R ₁₈ and R ₁₉ are selected from hydrogen, C ₁ -C ₃ alkyl, or fluoro-(C _r C ₃ )-alkyl, or R ₁₈ and R ₁₉ together with the nitrogen atom to which they are respectively attached, form an optionally substituted, 4- to 6-membered, monocyclic heterocyclic ring having no more than three additional heteroatoms independently selected from oxygen, sulphur and nitrogen;

Y is hydrogen, C ₁ -C ₃ alkyl, C ₁ -C ₃ alkoxy, or halo; and

Q is an optionally substituted 5-membered monocyclic heteroaryl ring.

The active compounds of formula (I) are inhibitors of CHK1 , and are useful for the treatment, prevention and suppression of a proliferative disease such as cancer in combination with radiotherapy or chemotherapy.

According to a further embodiment of the present invention there is provided the use of a compound of formula (I), or a pharmaceutically acceptable salt thereof, in the manufacture of a medicament for enhancing a therapeutic effect of radiation or chemotherapy in the treatment of cancer.

According to a further embodiment of the present invention there is provided a method of treatment of cancer comprising administration to a subject in need of such treatment an effective dose of the compound of formula (I), or a pharmaceutically acceptable salt thereof.

According to a further embodiment of the present invention there is provided a pharmaceutical composition comprising a compound of formula (I), or a

pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier.

Terminology

As used herein, the term "(C _a -C _b )alkyl" wherein a and b are integers refers to a straight or branched chain alkyl radical having from a to b carbon atoms. Thus when a is 1 and b is 6, for example, the term includes methyl, ethyl, n-propyl, isopropyl, n- butyl, isobutyl, sec-butyl, t-butyl, n-pentyl and n-hexyl. As used herein the term "divalent (C _a -C _b )alkylene radical" wherein a and b are integers refers to a saturated hydrocarbon chain having from a to b carbon atoms and two unsatisfied valences, such as -CH ₂ -, -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ -, - CH ₂ CH(CH ₃ )CH ₂ - and -CH ₂ C(CH ₃ ) ₂ CH ₂ -. For the avoidance of doubt, it is to be understood that a divalent branched chain (C _a -C _b )alkylene radical includes those wherein one of the carbons of the hydrocarbon chain is a ring carbon of a cycloalkyl ring (ie is a spiro centre), such as those of formulae (II):

As used herein, the term "fluoro-(C _a -C _b )-alkyl" wherein a and b are integers refers to a straight or branched chain alkyl radical having from a to b carbon atoms substituted by one or more fluoro atoms. The term includes, for example, fluoromethyl, difluoromethyl and trifluoromethyl.

As used herein the term "cycloalkyl" refers to a saturated carbocyclic radical having from 3-8 carbon atoms and includes, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl and cyclooctyl.

As used herein the term "carbocyclic" refers to a mono- or bi-cyclic radical whose ring atoms are all carbon, and includes monocyclic aryl, cycloalkyl, and cycloalkenyl radicals, provided that no single ring present has more than 8 ring members. A "carbocyclic" group includes a mono-bridged or multiply-bridged cyclic alkyl group.

As used herein the term "aryl" refers to a mono-, bi- or tri-cyclic carbocyclic aromatic radical. Illustrative of such radicals are phenyl, biphenyl and napthyl.

As used herein the unqualified term "heteroaryl" refers to a mono-, bi- or tri-cyclic aromatic radical containing one or more heteroatoms selected from S, N and O. Illustrative of such radicals are thienyl, benzthienyl, furyl, benzfuryl, pyrrolyl, imidazolyl, benzimidazolyl, thiazolyl, benzthiazolyl, isothiazolyl, benzisothiazolyl, pyrazolyl, oxazolyl, benzoxazolyl, isoxazolyl, benzisoxazolyl, isothiazolyl, triazolyl, tetrazolyl, benztriazolyl, thiadiazolyl, oxadiazolyl, pyridinyl, pyridazinyl, pyrimidinyl, pyrazinyl, triazinyl, indolyl and indazolyl. As used herein the unqualified term "heterocyclyl" or "heterocyclic" includes

"heteroaryl" as defined above, and in particular refers to a mono-, bi- or tri-cyclic non- aromatic radical containing one or more heteroatoms selected from S, N and O, to groups consisting of a monocyclic non-aromatic radical containing one or more such heteroatoms which is covalently linked to another such radical or to a monocyclic carbocyclic radical, and to a mono-, bi- or tri-cyclic non-aromatic radical containing one or more heteroatoms selected from S, N and O which is mono-bridged or multiply-bridged. Illustrative of such radicals are pyrrolyl, furanyl, thienyl, piperidinyl, imidazolyl, oxazolyl, isoxazolyl, thiazolyl, thiadiazolyl, pyrazolyl, pyridinyl, pyrrolidinyl, pyrimidinyl, morpholinyl, piperazinyl, indolyl, morpholinyl, benzfuranyl, pyranyl, isoxazolyl, benzimidazolyl, methylenedioxyphenyl, ethylenedioxyphenyl, maleimido and succinimido groups.

Unless otherwise specified in the context in which it occurs, the term "substituted" as applied to any moiety herein means substituted with at least one substituent, for example selected from (d-CβJalkyl, (CrC ₆ )alkoxy, hydroxy, hydroxy(CrC ₆ )alkyl, mercapto, mercapto(CrC ₆ )alkyl, (C _r C ₆ )alkylthio, halo (including fluoro and chloro), trifluoromethyl, trifluoromethoxy, nitro, nitrile (-CN), oxo, phenyl, -COOH, -COOR ^A , -COR ^A , -SO ₂ R ^A , -CONH ₂ , -SO ₂ NH ₂ , -CONHR ^A , -SO ₂ NHR ^A , -CONR ^A R ^B , -SO ₂ NR ^A R ^B , -NH ₂ , -NHR ^A , -NR ^A R ^B , -OCONH ₂ , -OCONHR ^A , -OCONR ^A R ^B , -NHCOR ^A ,

-NHCOOR ^A , -NR ^B COOR ^A , -NHSO ₂ OR ^A , -NR ^B SO ₂ OR ^A , -NHCONH ₂ ,

-NR ^A CONH ₂ , -NHCONHR ⁸ _, -NR ^A CONHR ^B , -NHCONR ^A R ^B _, or -NR ^A CONR ^A R ^B wherein R ^A and R ^B are independently a (C _r C ₅ )alkyl group, or R ^A and R ^B when attached to the same nitrogen may form a cyclic amino ring such as a morpholinyl, piperidinyl or piperazinyl ring. An "optional substituent" or "susbtituent" may be one of the foregoing substituent groups.

As used herein the term "salt" includes base addition, acid addition and quaternary salts. Compounds of the invention which are acidic can form salts, including pharmaceutically or veterinarily acceptable salts, with bases such as alkali metal hydroxides, e.g. sodium and potassium hydroxides, alkaline earth metal hydroxides e.g. calcium, barium and magnesium hydroxides, with organic bases e.g. N-ethyl piperidine, dibenzylamine and the like. Those compounds (I) which are basic can form salts, including pharmaceutically or veterinarily acceptable salts with inorganic acids, e.g. with hydrohalic acids such as hydrochloric or hydrobromic acids, sulphuric acid, nitric acid or phosphoric acid and the like, and with organic acids e.g. with acetic, tartaric, succinic, fumaric, maleic, malic, salicylic, citric, methanesulphonic and p-toluene sulphonic acids and the like.

For a review on suitable salts, see Handbook of Pharmaceutical Salts: Properties, Selection, and Use by Stahl and Wermuth (Wiley-VCH, Weinheim, Germany, 2002).

Compounds of the invention are expected to be isolatable as hydrates and solvates. The term 'solvate' is used herein to describe a molecular complex comprising the compound of the invention and a stoichiometric amount of one or more

pharmaceutically acceptable solvent molecules, for example, ethanol. The term 'hydrate' is employed when said solvent is water. Any reference herein to a compound of formula(l) is to be understood as including such hydrates and solvates.

Compounds with which the invention is concerned which may exist in one or more stereoisomeric form, because of the presence of asymmetric atoms or rotational restrictions, can exist as a number of stereoisomers with R or S stereochemistry at each chiral centre or as atropisomeres with R or S stereochemistry at each chiral axis. The invention includes all such enantiomers and diastereoisomers and mixtures thereof.

So-called 'pro-drugs' of the compounds of formula (I) are also within the scope of the invention. Thus certain derivatives of compounds of formula (I) which may have little or no pharmacological activity themselves can, when administered into or onto the body, be converted into compounds of formula (I) having the desired activity, for example, by hydrolytic cleavage. Such derivatives are referred to as 'prodrugs'. Further information on the use of prodrugs may be found in Pro-drugs as Novel Delivery Systems, Vol. 14, ACS Symposium Series (T. Higuchi and W. Stella) and Bioreversible Carriers in Drug Design, Pergamon Press, 1987 (ed. E. B. Roche, American Pharmaceutical Association).

Prodrugs in accordance with the invention can, for example, be produced by replacing appropriate functionalities present in the compounds of formula (I) with certain moieties known to those skilled in the art as 'pro-moieties' as described, for example, in Design of Prodrugs by H. Bundgaard (Elsevier, 1985). Also included within the scope of the invention are metabolites of compounds of formula (I), that is, compounds formed in vivo upon administration of the drug. Some examples of metabolites include

(i) where the compound of formula (I) contains a methyl group, an

hydroxymethyl derivative thereof (-CH ₃ -> -CH ₂ OH):

(ii) where the compound of formula (I) contains an alkoxy group, an hydroxy derivative thereof (-OR -> -OH),

(iii) where the compound of formula (I) contains a tertiary amino group, a secondary amino derivative thereof (-NR ¹ R ² -> -NHR ¹ or -NHR ² ),

(iv) where the compound of formula (I) contains a secondary amino group, a primary derivative thereof (-NHR ¹ -> -NH ₂ ),

(v) where the compound of formula (I) contains a phenyl moiety, a phenol derivative thereof (-Ph -> -PhOH), and

(vi) where the compound of formula (I) contains an amide group, a carboxylic acid derivative thereof (-CONH ₂ -> COOH).

Variable substituents present in compounds (I) will now be further described. It is to be understood in the further description that any disclosed substituent or substituent class may be present in any combination with any of the other disclosed substituent classes. Specific examples of the variable substituents include those present in the compounds of the Examples herein.

The groups R ₁ , R ₂ , R ₅ and R _&

R-i, R _∑ . R5 and R ₆ are independently selected from hydrogen, or small substituents such as hydroxy, methyl, trifluoromethyl, hydroxymethyl, methoxy, trifluoromethoxy, methylamino and dimethylamino. Currently it is preferred that R ₁ , R ₂ , R ₅ and R ₆ are each hydrogen.

The groups R ₃ and R ₄ R ₃ and R ₄ are hydrogen, hydroxy, Ci-C ₃ alkyl, fluoro-(C _r C ₃ )-alkyl, hydroxy-(C _r C ₃ )- alkyl, C ₁ -C ₃ alkoxy, fluoro-^-C^-alkoxy, hydroxy-(C ₁ -C ₃ )-alkoxy, -N(Rn)-R ₁₂ , -AIk- N(Rii)-Ri ₂ . -0-AIk-N(Rn)-R ₁₂ , -C(=O)OH, carboxy-(C _r C ₃ )-alkyl, or -C(=O)-NH-R ₁₃ .

In some embodiments of the invention, one of R ₃ and R ₄ is hydrogen and the other is selected from -N(Rn)-R ₁₂ , -AIk-N(R ₁₁ J-R ₁₂ , and -0-AIk-N(R ₁₁ J-R ₁₂ , especially the latter two. Currently it is preferred that R ₄ be hydrogen. R ₁₁ and R ₁₂ together with the nitrogen atom to which they are attached, may form an optionally substituted, 4- to 6- membered, monocyclic heterocyclic ring having no more than three additional heteroatoms independently selected from oxygen, sulphur and nitrogen. Preferred structures include those wherein R ₁₁ and R ₁₂ together with the nitrogen atom to which they are attached form an azetidine, pyrrolidine, piperidine, morpholine, or piperazine ring, optionally substituted by C ₁ -C ₃ alkyl, hydroxy-(C _r C ₃ )-alkyl, fluoro, or hydroxy. Particularly preferred are those compounds wherein R ₁₁ and R ₁₂ together with the nitrogen atom to which they are attached form 1-hydroxy-azetidin-3-yl, pyrrolidin-1-yl, piperidin-1-yl, morpholin-4-yl, piperazin-1-yl, 1-methyl-piperidin-4-yl, 1-fluoro- piperidin-4-yl, 1-hydroxy-piperidin-4-yl, 1-(hydroxymethyl)-piperidin-4-yl, or 1-methyl- piperazin-4-yl. In this subclass AIk may be, for example C ₁ -C ₆ alkylene, preferably methylene, or ethylene. In this subclass AIk may be, for example -CH ₂ -, -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ - or -CH ₂ CH(CH ₃ )CH ₂ - or a divalent branched chain alkylene radical - CH ₂ C(CHa) ₂ CH ₂ - or of formula (II):

In other embodiments of the invention, one of R ₃ and R ₄ is hydrogen and the other is selected from -N(Rn)-R ₁₂ , -AIk-N(Rn)-Ri ₂ , and -0-AIk-N(Rn)-Ri ₂ , especially the latter two, wherein R ₁₁ and R ₁₂ are independently selected from C ₁ -C ₃ alkyl, for example methyl and ethyl, or R ₁₁ is C ₁ -C ₃ alkyl, for example methyl or ethyl and R ₁₂ is -N(R ₁₈ )-Ri9 wherein R ₁₈ and R ₁₉ are independently selected from C ₁ -C ₃ alkyl, for example methyl and ethyl. In this subclass also AIk may be, for example -CH ₂ -, - CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ - or -CH ₂ CH(CH ₃ )CH ₂ - or preferably a divalent branched chain alkylene radical -CH ₂ C(CH ₃ ) ₂ CH ₂ - or of formula (II):

(H)

In other embodiments of the invention, one of R ₃ and R ₄ is hydrogen and the other is selected from -N(Rn)-Ri ₂ , -AIk-N(Rn)-Ri ₂ , Or -O-AIk-N(Rn)-R ₁₂ , wherein R ₁₁ is hydrogen or Ci-C ₃ alkyl, particularly methyl or ethyl, and R ₁₂ is hydroxy-(d-C ₆ )-alkyl, such as 2-hydroxy-ethyl. In this subclass also AIk may be, for example -CH ₂ -, -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ - or -CH ₂ CH(CH ₃ )CH ₂ - or preferably a divalent branched chain alkylene radical -CH ₂ C(CH ₃ ) ₂ CH ₂ - or of formula (II):

The group Y

Y is hydrogen, Ci-C ₃ alkyl, Ci-C ₃ alkoxy, or halo. Presently, it is preferred that Y is hydrogen, methyl, methoxy, or halo. Particularly preferred are those compounds wherein Y is hydrogen or methyl.

The group W

W is selected from -C(=O)-N(-Ri ₆ )- or -N(-R _i7 )-C(=O)-. R ₁₆ and Ri ₇ are selected from hydrogen C ₁ -C ₃ alkyl such as methyl and fluoro-(C ₁ -C ₃ )-alkyl such as

trifluoromethyl. Preferred structures include those wherein W is

-C(=O)-NH- (ie where the nitrogen is linked to the pyrazole ring, or

-NH-C(=O)- (ie where the carbonyl group is linked to the pyrazole ring), particularly the latter.

The radicals R ₇ and R ₈

R ₇ and R ₈ are independently selected from hydrogen, hydroxy, or C ₁ -C ₃ alkoxy.

Preferred structures include those wherein R ₇ and R ₈ are independently selected from hydrogen, hydroxy, or methoxy. Particularly preferred cases are wherein one or both of R ₇ and R ₈ is/are hydrogen.

The divalent radical X

X is a straight chain divalent C ₁ -C ₃ alkylene radical, optionally substituted on one or more carbons by R ₉ and/or R ₁₀ . R ₉ and R ₁₀ are independently selected from methyl, hydroxy, or fluoro. Currently, it is preferred that both R ₉ and Ri ₀ when present are methyl. For example, X may be -CH ₂ -, -CH(CH ₃ )- or

-C(CHa) ₂ -.

The group Q Q is selected from optionally substituted 5-membered monocyclic heteroaryl ring. Examples of such rings include thienyl, furyl, pyrrolyl, imidazolyl, thiazolyl, isothiazolyl, pyrazolyl, oxazolyl, isoxazolyl, triazolyl, tetrazolyl thiadiazolyl, and oxadiazolyl,

In a subclass of compounds with which the invention is concerned, Q is unsubstituted or substituted 2-thienyl or 4-isoxazolyl.

When substituents are present in Q ₁ the ring may be substituted by one or two substituents independently selected from C ₁ -C ₃ alkyl, halo-(Ci-C ₃ )alkyl, C _r C ₃ alkoxy, halo, or cyano. Preferred substituents are methyl, trifluoromethyl, methoxy, fluoro, chloro, or cyano. Preferred structures include those wherein Q is 5-chloro-thien-2-yl or 3,5-dimethyl-isoxazol-4-yl.

In a currently preferred subclass of compounds of formula (I) of the invention, R ₁ , R ₂ , R4, R5, Re, Rr and R ₈ are each hydrogen; Y is hydrogen or methyl; W is -NH-C(=O)- wherein the carbonyl group is linked to the pyrazole ring; R ₃ is -N(Rn)-R ₁₂ , -AIk- N(R ₁₁ J-R ₁₂ , or -0-AIk-N(Rn)-R ₁₂ ; R ₁₁ and R ₁₂ together with the nitrogen atom to which they are attached form an optionally substituted, 5- to 6-membered, monocyclic heterocyclic ring having no more than three additional heteroatoms independently selected from oxygen, sulphur and nitrogen, or R ₁₁ and R ₁₂ are independently selected from methyl and ethyl; AIk is -CH ₂ -, -CH ₂ CH ₂ -, -CH ₂ CH ₂ CH ₂ - or - CH ₂ C(CHa) ₂ CH ₂ -; X is -CH ₂ -, -CH(CH ₃ )- or -C(CHs) ₂ -; and Q is optionally substituted furyl, pyrrolyl, imidazolyl, thiazolyl, isothiazolyl, pyrazolyl, oxazolyl, triazolyl, tetrazolyl, thiadiazolyl, or oxadiazolyl, or especially thienyl or isoxazolyl optionally substituted by one or two substituents selected from C ₁ -C ₃ alkyl, fluoro-(C _r C ₃ )alkyl, C ₁ -C ₃ alkoxy, fluoro-(C _r C ₃ ) alkoxy, halo, and cyano. In this preferred subclass, R ₁₁ and R ₁₂ together with the nitrogen atom to which they are attached may form a piperidine, morpholine, or piperazine ring, optionally substituted by C ₁ -C ₃ alkyl or fluoro.

Specific compounds of the invention include those of the Examples herein, and their pharmaceutically acceptable salts.

Utility

The present invention may be employed in respect of a human or animal subject, more preferably a mammal, more preferably a human subject. As used herein, the term "treatment" as used herein includes prophylactic treatment.

Compounds of the invention may be used alone in the treatment of cancers and autoimmune disorders such as organ transplant rejection, lupus, multiple sclerosis, rheumatoid arthritis and osteoarthritis. However, as explained above in the background to the present invention, the main utility of inhibitors of CHK1 is considered to be their ability to improve the efficacy of current DNA-damage inducing radiotherapy or chemotherapeutic regimens for cancer treatment. The compound of formula (I) is therefore preferably used in combination for the treatment of cancer with radiation therapy or one or more cytotoxic or cytostatic drugs, or drugs which induce cytotoxicity or cytostasis. The compound of the invention and the other component may be in the same pharmaceutical formulation or in separate formulations for administration simultaneously or sequentially.

Non-limiting examples of chemotherapeutic agents, radiotheraputic agents and other active and ancillary agents are set forth below.

(i) Alkylating agents.

(ii) Nitrogen mustards such as

chlorambucil

cyclophosphamide

ifosfamide

mechlorethamine

melphalan

(iii) Nitrosoureas such as

carmustine (BCNU)

lomustine (CCNU)

semustine (methyl-CCNU)

(iv) Ethylenimine/Methyl-melamine such as

hexamethylmelamine (HMM / altetamine)

thriethylenemelamine (TEM)

trethylene thiophosphoramide (thiotepa) (v) Alkyl sulphonates such as busulphan.

(vi) Triazines such as dacarbazine (DTIC).

(vii) Antimetabolites such as the Folic acid analogues such as

Methotrexate

pemetrexed (multi-targeted antifolate)

Trimetrexate

(viii) Pyrimidine analogues such as

2,2'-difluorodeoxy-cytidine

5-azacytidine

5-fluorouracil

cytosine arabinoside (araC / cytarabine)

Fluorodeoxyuridine

Gemcitabine

(ix) Purine analogues such as

2-chlorodeoxyadenosine (cladribine / 2-CdA)

2'-deoxycoformycin (pentostatin)

6-Mercaptopurine

6-thioguanine

Azathioprine

erthyrohydroxynonyl-adenine (EHNA)

fludarabine phosphate

(x) Type I Topoisomerase Inhibitors such as

camptothecin

irinotecan

topotecan

(xi) Biological response modifiers such as G-CSF and GM-CSF.

(xii) Differentiation agents such as retinoic acid derivatives.

(xiii) Hormones and antagonists. (xiv) Adrenocorticosteroids/antagonists such as ainoglutethimide

dexamethasone

prednisone and equivalents

(xv) Progestins such as

hydroxyprogesterone caproate

medroxyprogesterone acetate

megestrol acetate

(xvi) Estrogens such as

diethylstilbestrol

ethynyl estradiol / equivalents

(xvii) Antiestrogens such as tamoxifen.

(xviii) Andogens such as

testosterone propionate

fluoxymesterone / equivalents

(xix) Anti-androgens such as

Flutimide

gonadotropin-releasing hormone analogues

Leuprolide

(xx) Nonsteroidal antiandrogens.

(xxi) Natural products.

(xxii) Antimitotic drugs.

(xxiii) Taxanes such as

docetaxel (Taxotere)

estramustine I estramustine phosphate Paclitaxel vinblastine (VLB)

vinca alkaloids

Vincristine

Vinorelbine

(xxiv) Epipodophylotoxins such as etoposide or teniposide.

(xxv) Antibiotics such as

actimomycin D

aphidicolin

Bleomycin

Dactinomycin

daunomycin (rubidomycin)

doxorubicin (adriamycin)

mitomycin C

Mitroxantroneidarubicin

splicamycin (mithramycin)

(xxvi) Enzymes such as L-asparaginase and L-arginase.

(xxvii) Radiosensitizers such as

5-bromodeoxyuridine

5-iododeoxyuridine

Bromodeoxycytidine

Desmethylmisonidazole

EO9

Etanidazole

Metronidazole

Misonidazole

Nicotinamide

Nimorazole

Pimonidazole

RB 6145

RSU 1069

SR4233 (xxviii) Platinum coordination complexes such as

Anthracenedione

Carboplatin

Cisplatin

Mitoxantrone

oxaliplatin

(xxix) Substituted ureas such as hydroxyurea.

(xxx) Methylhydrazine derivatives such as N-methylhydrazine (MIH) and procarbazine.

(xxxi) Adrenocortical suppressant mitocane (o,p'-DDD) ainoglutethimide. (xxxii) Cytokines such as interferon (α, β, γ) and interleukin-2. (xxxiii) Photosensitisers such as

bacteriochlorophyll-a

benzoporphyrin derivatives

hematoporphyrin derivatives

napthalocyanines

Npe6

pheboride-a

photofrin

phthalocyanines

tin etioporphyrin (SnET2)

zinc phthalocyanines

(xxxiv) Radiation such as

gamma radiation

infrared radiation

microwave radiation

ultraviolet light

visible light

X-ray It will be understood that the specific dose level for any particular patient will depend upon a variety of factors including the activity of the specific compound employed, the age, body weight, general health, sex, diet, time of administration, route of administration, rate of excretion, drug combination and the causative mechanism and severity of the particular disease undergoing therapy. In general, a suitable dose for orally administrable formulations will usually be in the range of 0.1 to 3000 mg, once, twice or three times per day, or the equivalent daily amount administered by infusion or other routes. However, optimum dose levels and frequency of dosing will be determined by clinical trials as is conventional in the art.

The compounds with which the invention is concerned may be prepared for administration by any route consistent with their pharmacokinetic properties. The orally administrable compositions may be in the form of tablets, capsules, powders, granules, lozenges, liquid or gel preparations, such as oral, topical, or sterile parenteral solutions or suspensions. Tablets and capsules for oral administration may be in unit dose presentation form, and may contain conventional excipients such as binding agents, for example syrup, acacia, gelatin, sorbitol, tragacanth, or polyvinylpyrrolidone, fillers for example lactose, sugar, maize-starch, calcium phosphate, sorbitol or glycine, tabletting lubricant, for example magnesium stearate, talc, polyethylene glycol or silica, disintegrants for example potato starch, or acceptable wetting agents such as sodium lauryl sulphate. The tablets may be coated according to methods well known in normal pharmaceutical practice. Oral liquid preparations may be in the form of, for example, aqueous or oily suspensions, solutions, emulsions, syrups or elixirs, or may be presented as a dry product for reconstitution with water or other suitable vehicle before use. Such liquid

preparations may contain conventional additives such as suspending agents, for example sorbitol, syrup, methyl cellulose, glucose syrup, gelatin hydrogenated edible fats, emulsifying agents, for example lecithin, sorbitan monooleate, or acacia, nonaqueous vehicles (which may include edible oils), for example almond oil, fractionated coconut oil, oily esters such as glycerine, propylene glycol, or ethyl alcohol, preservatives, for example methyl or propyl p-hydroxybenzoate or sorbic acid, and if desired conventional flavouring or colouring agents.

For topical application to the skin, the drug may be made up into a cream, lotion or ointment. Cream or ointment formulations which may be used for the drug are conventional formulations well known in the art, for example as described in standard textbooks of pharmaceutics such as the British Pharmacopoeia.

The active ingredient may also be administered parenterally in a sterile medium. Depending on the vehicle and concentration used, the drug can either be suspended or dissolved in the vehicle. Advantageously, adjuvants such as a local anaesthetic, preservative and buffering agents can be dissolved in the vehicle.

There are multiple synthetic strategies for the synthesis of the compounds (I) with which the present invention is concerned, but all rely on known chemistry, known to the synthetic organic chemist. Thus, compounds according to formula (I) can be synthesised according to procedures described in the standard literature and are well-known to the one skilled in the art. Typical literature sources are "Advanced Organic Chemistry", 4 ^th Edition (Wiley), J March, "Comprehensive Organic

Transformation", 2 ^nd Edition (Wiley), R.C. Larock , "Handbook of Heterocyclic Chemistry", 2 ^nd Edition (Pergamon), A.R. Katritzky), review articles such as found in "Synthesis", "Ace. Chem. Res." , "Chem. Rev", or primary literature sources identified by standard literature searches online or from secondary sources such as "Chemical Abstracts" or "Beilstein". Such literature methods include those of the preparative Examples herein, and methods analogous thereto.

Examples of methods known in the art of organic chemistry in general, by which the compounds of the present invention may be prepared, are included in the following reaction schemes and procedures. Scheme 1

de) (1f)

Scheme 2

Scheme 3

(3g) EXAMPLES

The following examples illustrate the preparation of specific compounds of the invention and are not intended to be limiting of the full scope of the invention.

Example 1: i-tS-Chloro-thiophen^-ylmethvD-IH-pyrazole^-carboxylic acid T5- (1 H-indol-2-yl)-6-oxo-1 ,6-dihvdro-pyridin-3-yll-amide

The title compound was prepared according to the route outlined in Scheme 1.

Step 1 : Preparation of 3-lodo-5-nitro-1-(2-trimethylsilanyl-ethoxymethyl)-1H-pyridi n-2- one (1 a).

2-Hydroxy-3-iodo-5-nitro pyridine (26.6g, lOOmmol) was stirred in anhydrous 1 ,2- dimethoxyethane (50OmL) at ambient temperature and lithium hydroxide monohydrate (8.5g, 203mmol) was added. The reaction mixture was cooled to 5 ⁰ C using ice/water and then 2-(trimethylsilyl)ethoxymethyl chloride (18.84g, 2OmL, 113mmol) was added dropwise and the reaction stirred at ambient temperature for 2 hours. The reaction mixture was diluted with diethyl ether (100OmL) and the mixture washed with 2M aqueous sodium hydroxide solution (2x200mL) and then 20% aqueous sodium thiosulphate solution (20OmL) and finally water (3x200mL). The solution was dried over anhydrous sodium sulphate and concentrated to an orange oil. The resultant crude product was purified by flash chromatography on SiO ₂ eluting with hexane - 20% ethyl acetate / hexane (gradient). The title compound was isolated as a yellow oil, 26.9g, 68%.

Step 2: Preparation of 2-[5-Nitro-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl)-1 ,2- dihydro-pyridin-3-yl]-indole-1-carboxylic acid tert-butyl ester (1 b). To a stirred solution of Intermediate (1a), 3-iodo-5-nitro-1-(2-trimethylsilanyl- ethoxymethyl)-1 H-pyridin-2-one (8.92g, 22.5mmol) in THF (12OmL) was added 1- (tert-butoxycarbonyl) indole-2-boronic acid (6.47g, 24.8mmol) followed by potassium carbonate (9.34g, 67.5mmol) and water (2OmL). [1 ,1 'bis(diphenylphosphino) ferrocene] dichloro palladium(ll) complex with CH ₂ CI ₂ (1 :1) (0.919g, 5mol%) was added and the mixture was thoroughly degassed prior to heating at 6O ⁰ C for 2hrs. After cooling, the reaction mixture was diluted with ethyl acetate (10OmL) and washed with saturated sodium hydrogen carbonate solution (5OmL) and then brine. The organics were filtered through a plug of celite, dried (MgSO ₄ ) and concentrated in vacuo. The resultant crude product was purified by flash chromatography on SiO ₂ eluting with hexane - 20% ethyl acetate / hexane (gradient) and then via trituration with isohexaπe to furnish the title compound as a white solid, 8.5g, 78%.

Step 3: Preparation of 2-[5-[(1-Benzyl-1 H-pyrazole-4-carbonyl)-amino]-2-oxo-1-(2- trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1 -carboxylic acid tert- butyl ester (1c).

Zinc powder (6.54g, 100mmol) was added to a suspension of Intermediate (1 b), 2-[5- nitro-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1- carboxylic acid tert-butyl ester (4.85g, lOmmol) in methanol (75mL). Ammonium chloride (0.55g, 10.3mmol) was added and the reaction was heated at 75 ⁰ C for 30mins. After cooling, the mixture was filtered through celite and the filter cake washed through with ethyl acetate (50OmL). The filtrate was washed with water (2x200mL), brine (15OmL), dried (Na ₂ SO ₄ ) and concentrated in vacuo to afford the desired title compound as a dark green foam, 4.55g, quantitative.

Step 4: Preparation of 2-[5-{[1-(5-Chloro-thiophen-2-ylmethyl)-1H-pyrazole-4- carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]- indole-1 -carboxylic acid tert-butyl ester (1d)

To a solution of (1c), 2-[5-[(1-benzyl-1 H-pyrazole-4-carbonyl)-amino]-2-oxo-1-(2- trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1 -carboxylic acid tert- butyl ester (0.38g, 0.833mmol) and triethylamine (0.202mg, 0.278mL, 2mmol) in dichloromethane (1OmL) at O ⁰ C was added dropwise a solution of intermediate (1e), (which was prepared according to the protocol below), 1-(5-chloro-thiophen-2- ylmethyl)-1 H-pyrazole-4-carbonyl chloride (0.26g, 1mmol) in dichloromethane (5mL). After addition the reaction mixture was stirred at ambient temperature for 1 hour and then partitioned between dichloromethane (25mL) and aqueous saturated sodium hydrogen carbonate solution (2OmL). The organic layer was separated and washed with brine several times, dried (Na ₂ SO ₄ ) and concentrated in vacuo. The resultant crude product was purified by flash chromatography on SiO ₂ eluting with hexane - 20% ethyl acetate / hexane - 50% ethyl acetate / hexane (gradient) to afford the desired title compound as a pink solid, 0.31g, 55%.

Step 5: Preparation of the Title Compound: 1-(5-Chloro-thiophen-2-ylmethyl)-1H- pyrazole-4-carboxylic acid [5-(1 H-indol-2-yl)-6-oxo-1 ,6-dihydro-pyridin-3-yl]-amide Intermediate (1d), 2-[5-{[1-(5-chloro-thiophen-2-ylmethyl)-1 H-pyrazole-4-carbonyl]- amino}-2-oxo-1 -(2-trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1 - carboxylic acid tert-butyl ester (0.144g, 0.211mmol) was stirred in tetrahydrofuran (5ml_) and 1 ,2-diaminoethane (60mg, 67uL, 1mmol) was added followed by tetrabutylammonium fluoride solution 1.0M in tetrahydrofuran (1mL, 1mmol). The reaction mixture was heated at reflux for 42 hours, and cooled to ambient temperature. The reaction mixture was concentrated in vacuo and the residue was partitioned between water and ethyl acetate. The organic layer was separated and the aqueous was extracted with a further portion of ethyl acetate and the combined ethyl acetate layers were washed with water (x4), dried (Na ₂ SO ₄ ) and concentrated in vacuo. The resultant crude product was purified by flash chromatography on SiO ₂ eluting with 50% ethyl acetate / dichloromethane and then 5% methanol / dichloromethane to afford a yellow solid. This solid was further purified via trituration with water to afford the desired title compound as a yellow solid, 33mg, 35%.

LC/MS: RT = 2.41 Min (270nm), m/z = 448 [M-H]. Total run time 3.75 min (short pos / neg).

¹ H NMR (dβ DMSO): δ 5.56 (s, 2H), 6.95-7.02 (m, 1H), 7.03-7.11 (m, 4H), 7.49-7.55

(t, 2H), 7.81 (d, 1 H), 8.05 (s, 1 H), 8.18 (d, 1 H), 8.40 (s, 1 H), 9.82 (br s, 1 H), 11.56 (br s, 1H), 12.02 (br s, 1H).

Preparation of 1-(5-Chloro-thiophen-2-ylmethyl)-1 H-pyrazole-4-carbonyl chloride (1f)

1 H-Pyrazole-4-carboxylic acid ethyl ester (0.763g, 5.45mmol) was stirred in acetone (15mL) with potassium carbonate (2.64g, 19mmol) and 2-chloro-5-chloromethyl- thiophene (1.Og, 5.99mmol) was added. The reaction was heated at 5O ⁰ C for 4 hours. The reaction was cooled and the inorganics were separated via filtration. The filter cake was washed through with ethyl acetate (2x1 OmL) and the combined washings and filtrate were concentrated in vacuo.

The residue was refluxed in a mixture of methanol (15mL) and H ₂ O (3ml) containing potassium hydroxide (0.83g, 12.5mmol), for 5 hours. The reaction was cooled and concentrated in vacuo. The residue was dissolved in H ₂ O and washed with ethyl acetate. The aqueous layer was separated and carefully acidified using an aqueous 6N hydrochloric acid solution. The resulting precipitate was filtered, washed with copious amounts of water and dried in vacuo to afford (1e), 1-(5-chtoro-thiophen-2- ylmethyl)-1H-pyrazole-4-carboxylic acid, 1.21g, 91%.

Hδ-Chloro-thiophen^-ylmethyO-I H-pyrazole^-carboxylic acid, (1e), (0.243g, 1 mmol) was stirred as a suspension in toluene (5ml_). Thionyl chloride (0.297g, 0.182mL, 2.5mmol) was added and the reaction mixture was refluxed for 3hrs. After cooling the reaction was concentrated in vacuo. Anhydrous toluene was added to the residue and concentrated in vacuo. This was repeated a further three times and the title compound, intermediate (1f), 1-(5-chloro-thiophen-2-ylmethyl)-1 H-pyrazole-4- carbonyl chloride, was isolated as a yellow oil, 0.261 g, quantitative.

Example 2: 1-(3,5-Dimethyl-isoxazol-4-ylmethyl)-1H-pyrazole-4-carboxyli c acid T5-(1 H-indol-2-yl)-6-oxo-1.6-dihydro-pyridin-3-yl1-amide

The title compound was prepared by the route outlined in Scheme 1 , following the same procedures as for Example 1 , except for the following modifications.

The penultimate step, amide coupling, was achieved using the following alternative to the procedure described for Example 1. 2-[5-[(1-Benzyl-1 H-pyrazole-4-carbonyl)-amino]-2-oxo-1-(2-trimethylsilanyl- ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1-carboxylic acid tert-butyl ester, (1c), (0.159g, 0.35mmol), 1-(3,5-dimethyl-isoxazol-4-ylmethyl)-1 H-pyrazole-4-carboxylic acid (0.093g, 0.42mmol) and triethylamine (0.071 g, 0.097mL, OJmmol) were stirred in acetonitrile for 5mins. 0-benzotriazole-N,N,N'-N'-tetramethyl-uronium-hexafluoro- phosphate (0.199g, 0.525mmol) was added and the reaction was stirred at RT for 18hrs. The reaction mixture was concentrated in vacuo and the residue was partitioned between ethyl acetate (25mL) and aqueous saturated sodium hydrogen carbonate solution (2OmL). The organic layer was separated and the aqueous was extracted with a further portion of ethyl acetate (25mL). The combined ethyl acetate layers were washed with brine, dried (Na ₂ SO ₄ ) and concentrated in vacuo. The resultant crude product was purified by flash chromatography on SiO ₂ eluting with first 50% ethyl acetate / hexane and then 50% ethyl acetate / DCM to afford the desired intermediate, 2-[5-{[1-(3,5-dimethyl-isoxazol-4-ylmethyl)-1 H-pyrazole-4- carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]- indole-1-carboxylic acid tert-butyl ester, as a blue oil, 0.22g, 96%.

The final step, global deprotection, was achieved using the following alternative to the procedure described for Example 1.

2-[5-{[1-(3,5-Dimethyl-isoxazol-4-ylmethyl)-1 H-pyrazole-4-carbonyl]-amino}-2-oxo-1- (2-trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1 -carboxylic acid tert-butyl ester, (0.22g, 0.334mmol) was stirred in tetrahydrofuran (3ml_) and 1,2- diaminoethane (0.1Og, 0.111mL, 1.67mmol) was added followed by tetrabutylammonium fluoride solution 1.0M in tetrahydrofuran (1.67mL, 1.67mmol). The reaction mixture was heated at 12O ⁰ C for 45 mins under microwave irradiation. After cooling the reaction mixture was concentrated in vacuo and the residue was partitioned between water and ethyl acetate. The organic layer was separated and the aqueous was extracted with a further portion of ethyl acetate and the combined ethyl acetate layers were washed with water (x4), dried (Na ₂ SO ₄ ) and concentrated in vacuo. The resultant crude product was purified by flash chromatography on SiO ₂ eluting with first 50% ethyl acetate / dichloromethane and then 5% methanol / dichloromethane to remove the impurities. The title compound was eluted using 1 % triethylamine / 9% methanol / 90% dichloromethane and was isolated as a yellow solid, 33mg, 23%.

LC/MS: RT = 2.12 Min (270nm), m/z = 427 [M-H]. Total run time 3.75 min (short pos / neg). ¹ H NMR (dβ DMSO): δ 2.16 (s, 3H), 2.45 (s, 3H), 5.24 (s, 2H), 6.96-7.01 (m, 1 H), 7.05-7.10 (m, 2H), 7.49-7.55 (m, 2H), 7.79-7.82 (d, 1 H), 8.01 (s, 1H), 8.17 (S ₁ 1 H), 8.37 (S, 1 H), 9.78 (s, 1 H), 11.56 (br s, 1 H), 12.02 (br s, 1 H).

Example 3: i-fS-Chloro-thiophen-Z-ylmethvD-IH-pyrazole^-carboxylic acid \6- oxo-5-(5-piperidin-1 -ylmethyl-1 H-indol-2-yl)-1 ,6-dihydro-pyridin-3-vn-amide

The title compound was prepared according to the route outlined in Scheme 2.

Step 1 : Preparation of (1 H-lndol-5-yl)-methanol (2a).

To a mechanically stirred solution of indole-5-carboxylic acid (26.3g, 163mmol) in tetrahydrofuran (60OmL), was added a solution of lithum aluminium hydride 1.0M in tetrahydrofuran (20OmL, 200mmol) dropwise at ambient temperature. A solution of lithium aluminium hydride 2.0M in tetrahydrofuran (22mL, 44mmol) was added dropwise at ambient temperature, and then the reaction mixture was carefully heated up to reflux and held there for 1 hour. The reaction mixture was cooled to ambient temperature and then water (13mL) was added dropwise, followed by an aqueous 10% sodium hydroxide solution (13mL), and water (2OmL). The suspension was stirred at ambient temperature for 30 minutes, filtered through a bed of celite and the filter cake washed with ethyl acetate (2x200mL). The filtrate and the washings were combined and the organics were separated, dried (Na ₂ SO ₄ ) and concentrated in vacuo, to give a dark red oil. The resultant crude product was suspended in hexane (20OmL), and ethyl acetate (1OmL) was added. This mixture was stirred at ambient temperature for 18 hours, and the solids were separated via filtration and washed with hexane to afford the title compound as a light brown solid, 22.25g, 93%.

Step 2: Preparation of δ-^ert-Butyl-dimethyl-silanyloxymethyO-indole-i-carboxylic acid tert-butyl ester (2b).

To a mechanically stirred solution of (1 H-lndol-5-yl)-methanol, (2a), (22.2g, 151mmol) in dichloromethane (30OmL) at ambient temperature was added N ₁ N- diisopropylethylamine (39.Og, 52.6mL, 302mmol) followed by a solution of tert- butyldimethylsilyl chloride (25g, 166mmol) in dichloromethane (40OmL). 4- Dimethylaminopyridine (1.84g, 15.1mmol) was added and the reaction was stirred at ambient temperature for 2 hours. The reaction mixture was concentrated in vacuo and the residue was taken up in ethyl acetate (40OmL), washed with an aqueous 0.5N hydrochloric acid solution (60OmL), brine, dried (Na ₂ SO ₄ ) and concentrated in vacuo to yield a red oil.

This red oil was dissolved in dichloromethane (35OmL) and to this was added di-tert- butyl dicarbonate (36.2g, 166mmol) dropwise at ambient temperature as a solution in dichloromethane (5OmL). 4-Dimethylaminopyridine (1.84g, 15.1 mmol) was added and the reaction stirred at ambient temperature for 2 hours. The reaction mixture was concentrated in vacuo and the residue was taken up in ethyl acetate (30OmL), washed with an aqueous 0.5N hydrochloric acid solution (20OmL), brine, dried (Na ₂ SO ₄ ) and concentrated in vacuo to yield a light brown oil. The resultant crude product was purified by flash chromatography on SiO ₂ eluting first with hexane and then 10% ethyl acetate / hexane to afford the desired title compound as a white solid, 52.22g, 96%.

Step 3: Preparation of 5-(tert-Butyl-dimethyl-silanyloxymethyl)-2-[5-nitro-2-oxo-1- (2- trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1 -carboxylic acid tert- butyl ester (2c).

To a solution of diisopropylamine (2.1g, 2.89mL, 20.8mmol) in anhydrous tetrahydrofuran (1OmL) was added butyllithium solution 2.5M in hexanes (7.71 mL, 19.3mmol) dropwise at -78 ⁰ C. After addition the reaction mixture was allowed to attain O ⁰ C, where it was stirred for 30 minutes to form the lithiumdiisopropyl amide solution. δ-Ctert-Butyl-dimethyl-silanyloxymethyO-indole-i-carboxylic acid tert-butyl ester (2b) (5.89g, 16.3mmol) was stirred in tetrahydrofuran (8OmL) and triisopropyl borate (4.18g, 5.13mL, 22.2mmol) was added, and the reaction mixture was cooled to -5 ⁰ C. To this was added the previously described lithiumdiisopropyl amide solution dropwise keeping the temperature between -5 ⁰ C and O ⁰ C. After addition the reaction was stirred at -5 ⁰ C for 30mins and then allowed to attain ambient temperature. The reaction mixture was concentrated in vacuo to yield crude indole-2-boronic acid-5- (tert-Butyl-dimethyl-silanyloxymethyl)-indole-i-carboxylic acid tert-butyl ester, which was dissolved in tetrahydrofuran (10OmL). Water (2OmL), potassium carbonate (6.17g, 44.6mmol), 3-iodo-5-nitro-1-(2-trimethylsilanyl-ethoxymethyl)-1 H-pyridin-2- one, intermediate (1a) (5.87g, 14.8mmol) in tetrahydrofuran (2OmL) and [1 ,1'- Bis(diphenylphosphino)ferrocene)]dichloropalladium(ll) complex with dichloromethane (0.605g, 5mol%) were added. The red suspension was degassed for 10 minutes and then heated at 6O ⁰ C for 2 hours. The reaction mixture was cooled and was partitioned between ethyl acetate (20OmL) and aqueous saturated sodium bicarbonate solution (20OmL). The organic layer was separated and the aqueous was extracted with a further portion of ethyl acetate. The combined ethyl acetate layers were washed with brine, dried (Na ₂ SO ₄ ), filtered through a plug of celite and concentrated in vacuo. The resultant crude product was purified by flash chromatography on SiO ₂ eluting with hexane - 15% ethyl acetate / hexane (gradient) to afford the desired title compound as a yellow solid, 8.44g, 90%.

Step 4: Preparation of 2-[5-Amino-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl)-1,2- dihydro-pyridin-S-yll-δ-^ert-butyl-dimethyl-silanyloxymethy O-indole-i-carboxylic acid tert-butyl ester (2d).

The title compound was prepared by the route outlined in Scheme 2 and using the experimental from Example 1 , Step 3, with intermediate (2c) 5-(tert-butyl-dimethyl- silanyloxymethyl)-2-[5-nitro-2-oxo-1-(2-trimethylsilanyl-eth oxymethyl)-1,2-dihydro- pyridin-3-yl]-indole-1-carboxylic acid tert-butyl ester (3.2g, 5.08mmol). In this instance ammonium formate was used instead of ammonium chloride. The title compound was obtained as a green foam, 3.05g, quantitative.

Step 5: Preparation of 5-(tert-Butyl-dimethyl-silanyloxymethyl)-2-[5-{[1-(5-chloro- thiophen-2-ylmethyl)-1 H-pyra2ole-4-carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl- ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1-carboxylic acid tert-butyl ester (2e) The title compound was prepared by the route outlined in Scheme 2 and using the experimental from Example 1 , step 4, with intermediate (2d), 2-[5-amino-2-oxo-1-(2- trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-5-(tert-butyl-dimethyl- silanyloxymethyl)-indole-1-carboxylic acid tert-butyl ester (0.624g, 1.04mmol) and intermediate 1(f), HS-chloro-thiophen-Σ-ylmethyO-IH-pyrazole^-carbonyl chloride (0.326g, 1.25mmol).

The resultant crude product was purified by flash chromatography on SiO ₂ with 20% ethyl acetate / hexane - 40% ethyl acetate / hexane (gradient) to afford the title compound as a pale green solid, 0.74g, 86%.

Step 6: Preparation of 2-[5-{[1-(5-Chloro-thiophen-2-ylmethyl)-1 H-pyrazole-4- carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-5 -formyl-indole-1-carboxylic acid tert-butyl ester (2f)-

Intermediate 2(e), 5-(tert-butyl-dimethyl-silanyloxymethyl)-2-[5-{[1 -(5-chloro-thiophen- 2-ylmethyl)-1 H-pyrazole-4-carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl- ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1-carboxylic acid tert-butyl ester (0.73g, 0.885mmol) was stirred in tetrahydrofuran (1OmL) and cooled to O ⁰ C. Tetrabutylammonium fluoride solution 1.0M in tetrahydrofuran (0.93mL, 0.93mmol) was added dropwise at O ⁰ C, and then the reaction was allowed to attain ambient temperature, where it was stirred for a further 2hours. The reaction mixture was diluted with ethyl acetate (3OmL), washed with water (3OmL), aqueous 0.5N hydrochloric acid solution (3OmL), brine, dried (Na ₂ SCIf) and concentrated in vacuo to yield a green foam.

This green foam was dissolved in anhydrous dichloromethane (2OmL) and manganese dioxide (0.96g, 11mmol) was added. The reaction was refluxed for 5 hours and, after cooling, the mixture was filtered through a bed of celite. The filter cake was washed through with tetrahydrofuran (2OmL) and the filtrate was concentrated in vacuo. The resultant crude product was purified by flash chromatography on SiO ₂ with hexane - 70% ethyl acetate / hexane (gradient) and then further purified by trituration with 5% ethyl acetate / hexane to afford the title compound as an off-white solid, 0.31Og ₁ 49%.

Step 7: Preparation of 2-[5-{[1-(5-Chloro-thiophen-2-ylmethyl)-1H-pyrazole-4- carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-5

-piperidin-1-ylmethyl-indole-i-carboxylic acid tert-butyl ester (2g).

To a solution of intermediate (2f), 2-[5-{[1-(5-chloro-thiophen-2-ylmethyl)-1 H- pyrazole-4-carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl-etho xymethyl)-1 ,2-dihydro- pyridin-S-yll-δ-formyl-indole-i-carboxylic acid tert-butyl ester, (0.142g, 0.2mmol) in tetrahydrofuran (1OmL) was added piperidine (0.051 g, 0.6mmol) and this was stirred for δmins at RT. Sodium triacetoxyborohydride (0.170g, O.δmmol) was added and the reaction mixture was stirred at ambient temperature for 50hours and then diluted with ethyl acetate. The mixture was washed with saturated aqueous sodium bicarbonate solution, brine, dried (Na ₂ SO ₄ ) and concentrated in vacuo. The resultant crude product was purified by flash chromatography on SiO ₂ with first 50% ethyl acetate - heaxane and then 10% methanol - dichloromethane to afford the title compound as a pale green solid, 0.097g, 63%.

Step 8: Preparation of the Title Compound: 1-(5-Chloro-thiophen-2-ylmethyl)-1 H- pyrazole-4-carboxylic acid [6-oxo-5-(5-piperidin-1-ylmethyl-1 H-indol-2-yl)-1 ,6-dihydro- pyridin-3-yl]-amide

The title compound was prepared according to the experimental used in Example 2, final step, with intermediate 2(g), 2-[5-{t1-(5-chloro-thiophen-2-ylmethyl)-1H-pyrazole- 4-carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl) -1 ,2-dihydro-pyridin-3- yl]-5-piperidin-1-ylmethyl-indole-1-carboxylic acid tert-butyl ester. After the usual work, up the crude product was purified by trituration with acetonitrile and then trituration with 25% methanol / acetonitrile to afford the title compound as a yellow solid, 20mg, 30%.

LC/MS: RT = 2.00 Min (270nm), m/z = 545 [M-H]. Total run time 3.75 min (short pos / neg).

¹ H NMR (dβ DMSO): δ 1.34-1.42 (br s 2H) ₁ 1.44-1.51 (m, 4H), 2.28-2.38 (br s, 4H),

3.46 (br s,2H), 5.56 (s, 2H), 7.00-7.07 (m, 4H), 7.40-7.46 (m, 2H), 7.82 (d, 1H), 8.05

(s, 1 H), 8.17 (d, 1 H) ₁ 8.41 (s, 1 H), 9.83 (s, 1H), 11.51 (s, 1 H), 12.00 (br s, 1H).

Example 4: i-tS-Chloro-thiophen-Z-ylmethylH H-pyrazole-Φcarboxylic acid (5- f5-(3-dimethylamino-2,2-dimethyl-propoxy)-1H-indol-2-yll-6-o xo-1,6-dihvdro- pyridin-3-yl)-amide

The title compound was prepared according to the route outlined in Scheme 3.

Step 1 : Preparation of 5-(tert-Butyl-dimethyl-silanyloxy)-indole-1-carboxylic acid tert- butyl ester (3a).

The title compound was prepared by the route outlined in Scheme 3 and using the experimental from Example 3, Step 2, with intermediate 1H-lndol-5-ol (5.54g, 7.4mmol). The resultant crude product was purified by flash chromatography on SiO ₂ with hexane - 10% ethyl acetate / hexane (gradient) to afford the title compound as a white solid, 13.41g, 93%.

Step 2: Preparation of 5-(tert-Butyl-dimethyl-silanyloxy)-2-[5-nitro-2-oxo-1-(2- trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-indole-1-carboxylic acid tert- butyl ester (3b).

The title compound was prepared by the route outlined in Scheme 3 and using the experimental from Example 3, Step 3, with intermediate 5-(tert-butyl-dimethyl- silanyloxy)-indole-1-carboxylic acid tert-butyl ester (11a) (2.9Og, 8.3mmol) and (1a), 3-iodo-5-nitro-1-(2-trimethylsilanyl-ethoxymethyl)-1 H-pyridin-2-one (3g, 7.6mmol). The resultant crude product was purified by flash chromatography on SiO ₂ with hexane - 20% ethyl acetate / hexane (gradient) to afford after trituration using hexane, the title compound as a pale yellow solid, 3.67g, 79%.

Step 3: Preparation of 2-[5-Amino-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl)-1,2- dihydro-pyridin-3-yl]-5-(tert-butyl-dimethyl-silanyloxy)-ind ole-1 -carboxylic acid tert- butyl ester (3c).

The title compound was prepared by the route outlined in Scheme 3 and using the experimental from Example 3, Step 4, with intermediate (2b) 5-(tert-butyl-dimethyl- silanyloxy)-2-[5-nitro-2-oxo-1-(2-trimethylsilanyl-ethoxymet hyl)-1 ,2-dihydro-pyridin-3- yl]-indole-1 -carboxylic acid tert-butyl ester (3.1g, 5.03mmol). The desired intermediate was obtained as a dark green foam, 2.95g, quantitative.

Step 4: Preparation of 5-(tert-Butyl-dimethyl-silanyloxy)-2-[5-{[1-(5-chloro-thioph en-2- ylmethyl)-1H-pyrazole-4-carbonyl]-amino}-2-oxo-1-(2-trimethy lsilanyl-ethoxymethyl)-

1 ,2-dihydro-pyridin-3-yl]-indole-1 -carboxylic acid tert-butyl ester (3d).

The title compound was prepared by the route outlined in Scheme 3 and using the experimental from Example 1 , Step 4, with intermediate (3c), 2-[5-amino-2-oxo-1-(2- trimethylsilanyl-ethoxymethyl)-1,2-dihydro-pyridin-3-yl]-5-( tert-butyl-dimethyl- silanyloxy)-indole-1 -carboxylic acid tert-butyl ester (0.609g, 1.04mmol) and intermediate 1 (f), 1-(5-chloro-thiophen-2-ylmethyl)-1H-pyrazole-4-carbonyl chloride

(0.326g, 1.25mmol).

The resultant crude product was purified by flash chromatography on SiO ₂ with 20% ethyl acetate / hexane - 40% ethyl acetate / hexane (gradient) to afford the title compound as a pale green solid, 0.615g, 73%.

Step 5: Preparation of 2-[5-{[1-(5-Chloro-thiophen-2-ylmethyl)-1H-pyrazole-4- carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-5 -hydroxy-indole-1 -carboxylic acid tert-butyl ester (3e).

Intermediate 3(d), 5-(tert-butyl-dimethyl-silanyloxy)-2-[5-{[1-(5-chloro-thioph en-2- ylmethyl)-1H-pyrazole-4-carbonyl]-amino}-2-oxo-1-(2-trimethy lsilanyl-ethoxymethyl)- 1 ,2-dihydro-pyridin-3-yl]-indole-1 -carboxylic acid tert-butyl ester (0.59g, 0.728mmol) was stirred in tetrahydrofuran (1OmL) and cooled to O ⁰ C. Tetrabutylammonium fluoride solution 1.0M in tetrahydrofuran (0.75mL, 0.75mmol) was added dropwise at O ⁰ C, and then the reaction was allowed to attain ambient temperature, where it was stirred for a further 1hour. The reaction mixture was diluted with ethyl acetate (3OmL), washed with water (3OmL) ₁ aqueous 0.5N hydrochloric acid solution (3OmL), brine, dried (Na ₂ SO ₄ ) and concentrated in vacuo to yield a green foam, 0.507g, quantitative, which was used without further purification. Step 6: Preparation of 2-[5-{[1-(5-Chloro-thiophen-2-ylmethyl)-1H-pyrazole-4- carbonyl]-arnino}-2-oxo-1-(2-trimethylsilanyl-ethoxyrnethyl) -1 ,2-dihydro-pyridin-3-yl]-5 -(3-dimethylamino-2,2-dimethyl-propoxy)-indole-1-carboxylic acid tert- butyl ester (3f) To a solution of intermediate (3e), 2-[5-{[1-(5-chloro-thiophen-2-ylmethyl)-1H- pyrazole-4-carbonyl]-amino}-2-oxo-1-(2-trimethylsilanyl-etho xynnethyl)-1 ,2-dihydro- pyridin-3-yl]-5-hydroxy-indole-1-carboxylic acid tert-butyl ester (0.2g, 0.287mmol) in N,N-dimethylformamide (2OmL) was added intermediate (3g), (which was prepared according to the protocol below), (3-chloro-2,2-dimethyl-propyl)-dimethyl-amine hydrochloride (0.107g, 0.575mmol) and cesium carbonate (0.28g, 0.861 mmol). The reaction mixture was heated at 100 ⁰ C for 1 hour, and cooled to ambient temperature before partitioning between ethyl acetate and water. The ethyl acetate layer was separated and washed with brine (x4), dried (Na ₂ SO ₄ ) and concentrated in vacuo. The title compound was purified by flash chromatography on SiO ₂ eluting with first 50% ethyl acetate / dichloromethane and then 10% methanol / dichloromethane to afford the desired title compound as a pale yellow solid, 0.12g, 52%.

Step 7: Preparation of the Title Compound: 1-(5-Chloro-thiophen-2-ylmethyl)-1H

-pyrazole-4-carboxylic acid {5-[5-(3-dimethylamino-2,2-dimethyl-propoxy)-1 H-indol-2- yl]-6-oxo-1 ,6-dihydro-pyridin-3-yl}-amide

The title compound was prepared by the route outlined in Scheme 3, following the same experimental procedures as for Example 1 , Step 5, using intermediate (3f), 2-

[5-{[1-(5-chloro-thiophen-2-ylmethyl)-1 H-pyrazole-4-carbonyl]-amino}-2-oxo-1-(2- trimethylsilanyl-ethoxymethyl)-1 ,2-dihydro-pyridin-3-yl]-5-(3-dimethylamino-2,2- dimethyl-propoxy)-indole-1-carboxylic acid tert- butyl ester (0.104g, 0.128mmol).

The title compound was purified by flash chromatography on SiO ₂ eluting with first

5% methanol / dichloromethane and then 1% triethylamine / 9% methanol / dichloromethane to afford the desired title compound as a yellow solid, 0.049g, 66%.

LC/MS: RT = 2.01 Min (270nm), m/z = 577 [M-H]. Total run time 3.75 min (short pos / neg).

¹ H NMR (d _β DMSO): δ 0.97 (s, 6H), 2.21 (s, 6H), 2.24 (s, 2H), 3.68 (s, 2H), 5.56 (s,

2H), 6.72 (dd, 1 H), 6.92 (d, 1 H), 7.02 (d, 1 H), 7.04-7.08 (m, 2H), 7.40 (d, 1H), 7.84 (d, 1 H), 8.05 (S, 1H), 8.15 (d, 1 H), 8.41 (s, 1H) ₁ 9.84 (s, 1 H), 11.44 (br s, 1H), 12.00 (br s, 1 H).

Preparation of (3-chloro-2,2-dimethyl-propyl)-dimethyl-amine hydrochloride (3g) To a solution of 3-dimethylamino-2,2-dimethy!-propan-1-ol (5g, 38.1mmol) was added N.N-dimethylformamide (1 drop) and thionyl chloride (4.99g, 3.06mL, 41.9mmol) dropwise at ambient temperature. The reaction mixture was slowly heated to reflux and heating continued for a further 3 hours. After cooling, the reaction mixture was concentrated in vacuo and anhydrous toluene was added to the residue and concentrated in vacuo once again. This was repeated a further three times and then the solids were collected via filtration. The filter cake was washed well with toluene and then isohexane to give the desired intermediate as a light brown solid, 6.68g, 94%.

General Procedures

All reagents obtained from commercial sources were used without further purification.

Anhydrous solvents were obtained from commercial sources and used without further drying.

Flash chromatography was performed with pre-packed silica-gel cartridges (Strata

Si-1 , 61 A, Phenomenex, Cheshire, UK or IST Flash II, 54 A, Argonaut, Hengoed,

UK).

Thin layer chromatography was conducted with 5 x 10 cm plates coated with Merck

Type 60 F ₂₅₄ silica-gel.

Microwave heating was performed with a Biotage Initiator™ 2.0 instrument.

The compounds of the present invention were characterized by high performance liquid chromatography-mass spectroscopy (HPLC-MS) on either an Agilent HP1200 Rapid Resolution Mass detector 6140 multi mode source M/z range 150 to 1000 amu or an Agilent HP1100 Mass detector 1946D ESI source M/z range 150 to 1000 amu. The conditions and methods listed below are identical for both machines.

Column for 3.75 min run: Gemini 5μm, C18, 30 mm x 4.6mm (Phenomenex).

Temperature: 35C.

Column for 1.9 min run: LunaHST 2.5 μm, C18, 50 x 2 mm (Phenomenex).

Temperature: 55C. Mobile Phase: A - Water + 10 mMol / ammonium formate + 0.08% (v/v) formic acid at pH ca 3.5.

B - 95% Acetonitrile + 5% A + 0.08% (v/v) formic acid

Injection Volume: 2μL

"Short" method gradient table, either positive (pos) or positive and negative (pos / neg) ionisation

Detection: UV detection at 230, 254 and 270 nm.

The compounds of the present invention were also characterized by Nuclear Magnetic Resonance (NMR). Analysis was performed with a Bruker DPX400 spectrometer and proton NMR spectra were measured at 400 MHz. The spectral reference was the known chemical shift of the solvent. Proton NMR data is reported as follows: chemical shift (δ) in ppm, followed by the multiplicity, where s = singlet, d = doublet, t = triplet, q = quartet, m = multiplet, dd = doublet of doublets, dt = doublet of triplets, dm = doublet of multiplets, ddd = doublet of double doublets, td = triplet of doublets, qd = quartet of doublets and br = broad, and finally the integration.

IUPAC chemical names were generated using AutoNom Standard. Assay Protocols

(i) CHK1 Enzyme Assay

Assays for the CHK1 kinase activity were carried out by monitoring the phosphorylation of a synthetic peptide Chktide with the amino acid sequence, KKKVSRSGLYRSPSMPENLNRPR. The assay mixture containing the inhibitor and CHK1 enzyme was mixed together in a microtiter plate in a final volume of 50μl and incubated for 40 minutes at 30 ⁰ C.

The assay mixture contained 0.01 mM unlabeled ATP, O.δμCi ³³ P-γ-ATP, 14.8μM Chktide, 0.1mg/mL BSA, 5OmM Hepes-NaOH pH 7.5 and 12.5nM His-CHK1

(Invitrogen) enzyme. The reaction was stopped by adding 50μL of 5OmM phosphoric acid. 90μL of the mixture was transferred to a pre-wetted 96-well multi-screen MAPHNOB filtration plate (Millipore) and filtered on a vacuum manifold. The filter plate was washed with 3 successive additions of 200μl 5OmM phosphoric acid and then with 100μL methanol. The filtration plate was dried for 10 min at 65 ⁰ C, scintillant added and phosphorylated peptide quantified in a scintillation counter (Trilux, PerkinElmer).

The compounds tested in the above assay were assigned to one of three activity ranges, namely A = IC ₅₀ <100 nM, B = IC ₅₀ >100 nM and <500nM or C = IC ₅₀ >500nM and <1500nM as indicated in the table below.

Table of CHK1 Enzyme Activities

(ii) CHK1 Cellular Assay - Gemcitabine ECsn Assay

The gemcitabine EC ₅₀ assay was developed as a rapid method for screening CHK1 inhibitors to determine their relative cell activity. This assay utilises a feature of the effect of CHK1 inhibitors on gemcitabine toxicity. In the absence of a CHK1 inhibitor, gemcitabine acts predominantly as an anti-metbolite and therefore induces very little cell death, even at high concentrations. This can be as high as 70-80% survival at concentrations in excess of 1μM. However, in the presence of a CHK1 inhibitor, the mechanism of action of gemcitabine switches to a more classical cytotoxic mode of action. For example, the fraction of cells surviving can be reduced to around 30% and below.

Concentrations of gemcitabine can be selected that in the absence of a CHK1 inhibitor, have no effect on cell survival but in the presence of a CHK1 inhibitor are highly cytotoxic. 10000 HT29 cells were plated per well of a 96 well plate and allowed to attach at 37°C in a 5% CO2 humidified incubator for 18 hours. CHK1 inhibitors were then titrated in the presence of 10, 15 and 2OnM gemcitabine for 72 hours and the EC5 ₀ determined by staining with sulforhodamine B (SRB) and determining the absorbance at 540nm.

The compounds were tested in the above assay in the presence of gemcitabine at 1OnM, and assigned to one of three activity ranges, namely A = EC ₅₀ <100 nM, B = EC ₅₀ >100 nM and <500nM or C = IC ₅₀ >500nM and <1500nM and some examples are given below.

Table of CHK1 Cellular Activities