2-(pyridin-2-ylamino)-pyrido[2,3, d]pyrimidin-7-ones

1. A method of treating breast cancer in a mammal comprising administering to said mammal an amount of a compound of formula I:

or a pharmaceutically acceptable salt thereof, wherein:

the dashed line represents an optional bond,

X 1 , X 2 , and X 3 are independently hydrogen, halogen, C 1 -C 6 alkyl, C 1 -C 6 haloalkyl, C 1 -C 8 alkoxy, C 1 -C 8 alkoxyalkyl, CN, NO 2 , OR 5 , NR 5 R 6 , CO 2 R 5 , COR 5 , S(O) n R 5 , CONR 5 R 6 , NR 5 COR 6 , NR 5 SO 2 R 6 , SO 2 NR 5 R 6 , and P(O)(OR 5 )(OR 6 ); with the proviso that at least one of X 1 , X 2 , and X 3 must be hydrogen;

n=0-2;

R 1 is C 1 -C 6 alkyl,

R 2 and R 4 are independently selected from hydrogen, halogen, C 1 -C 8 alkyl, C 3 -C 7 cycloalkyl, C 1 -C 8 alkoxy, C 1 -C 8 alkoxyalkyl, C 1 -C 8 haloalkyl, C 1 -C 8 hydroxyalkyl, C 2 -C 8 alkenyl, C 2 -C 8 alkynyl, nitrile, nitro, OR 5 , SR 5 , NR 5 R 6 , N(O)R 5 R 6 , P(O)(OR 5 )(OR 6 ), (CR 5 R 6 ) m NR 7 R 8 , COR 5 , (CR 4 R 5 ) m C(O)R 7 , CO 2 R 5 , CONR 5 R 6 , C(O)NR 5 SO 2 R 6 , NR 5 SO 2 R 6 , C(O)NR 5 OR 6 , S(O) n R 5 , SO 2 NR 5 R 6 , P(O)(OR 5 )(OR 6 ), (CR 5 R 6 ) m P(O)(OR 7 )(OR 8 ), (CR 5 R 6 ) m -aryl, (CR 5 R 6 ) m -heteroaryl, -T(CH 2 ) m QR 5 , —C(O)T(CH 2 ) m QR 5 , NR 5 C(O)T(CH 2 ) m QR 5 , and -CR 5 =CR 6 C(O)R 7 ;

T is O, S, NR 7 , N(O)R 7 , NR 7 R 8 W, or CR 7 R 8 ;

Q is O, S, NR 7 , N(O)R 7 , NR 7 R 8 W, CO 2 , O(CH 2 ) m -heteroaryl, O(CH 2 ) m S(O) n R 8 , (CH 2 )-heteroaryl, or a carbocyclic group containing from 3-7 ring members, up to four of which ring members are optionally heteroatoms independently selected from oxygen, sulfur, and nitrogen, provided, however, that there is at least one carbon atom in the carbocyclic ring and that if there are two or more ring oxygen atoms, the ring oxygen atoms are not adjacent to one another, wherein the carbocyclic group is unsubstituted or substituted with one, two, or three groups independently selected from halogen, hydroxy, hydroxyalkyl, lower alkyl, lower alkoxy, alkoxycarbonyl, alkylcarbonyl, alkylcarbonylamino, aminoalkyl, trifluoromethyl, N-hydroxyacetamide, trifluoromethylalkyl, amino, and mono or dialkylamino;

W is an anion selected from the group consisting of chloride, bromide, trifluoroacetate, and triethylammonium;

m=0-6;

R 4 and one of X 1 , X 2 and X 3 may form an aromatic ring containing up to three heteroatoms independently selected from oxygen, sulfur, and nitrogen, and optionally substituted by up to 4 groups independently selected from halogen, hydroxy, hydroxyalkyl, lower alkyl, lower alkoxy, alkoxycarbonyl, alkylcarbonyl, alkylcarbonylamino, aminoalkyl, aminoalkylcarbonyl, trifluoromethyl, trifluoromethylalkyl, trifluoromethylalkylaminoalkyl, amino, mono- or dialkylamino, N-hydroxyacetamido, aryl, heteroaryl, carboxyalkyl, nitrile, NR 7 SO 2 R 8 , C(O)NR 7 R 8 , NR 7 C(O)R 8 , C(O)OR 7 , C(O)NR 7 SO 2 R 8 , (CH 2 ) m S(O) n R 7 , (CH 2 ) m -heteroaryl, O(CH 2 ) m -heteroaryl, (CH 2 ) m C(O)NR 7 R 8 , O(CH 2 ) m C(O)OR 7 , (CH 2 ) m SO 2 NR 7 R 8 , and C(O)R 7 ;

R 3 is, C 1 -C 8 alkoxy, C 3 -C 7 cycloalkyl, or C 3 -C 7 -heterocyclyl;

R 5 and R 6 independently are hydrogen, C 1 -C 8 alkyl, C 2 -C 8 alkenyl, C 2 -C 8 alkynyl, arylalkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, or heteroarylalkyl; or

R 5 and R 6, when attached to the same nitrogen atom, taken together with the nitrogen to which they are attached, form a heterocyclic ring containing from 3-8 ring members, up to four of which members can optionally be replaced with heteroatoms independently selected from oxygen, sulfur, S(O), S(O) 2 , and nitrogen, provided, however, that there is at least one carbon atom in the heterocyclic ring and that if there are two or more ring oxygen atoms, the ring oxygen atoms are not adjacent to one another, wherein the heterocyclic group is unsubstituted or substituted with one, two or three groups independently selected from halogen, hydroxy, hydroxyalkyl, lower alkyl, lower alkoxy, alkoxycarbonyl, alkylcarbonyl, alkylcarbonylamino, aminoalkyl, aminoalkylcarbonyl, trifluoromethyl, trifluoromethylalkyl, trifluoromethylalkylaminoalkyl, amino, nitrile, mono- or dialkylamino, N-hydroxyacetamido, aryl, heteroaryl, carboxyalkyl, NR 7 SO 2 R 8 , C(O)NR 7 R 8 , NR 7 C(O)R 8 , C(O)OR 7 , C(O)NR 7 SO 2 R 8 , (CH 2 ) m S(O) n R 7 , (CH 2 ) m -heteroaryl, O(CH 2 ) m -heteroaryl, (CH 2 ) m C(O)NR 7 R 8 , O(CH 2 ) m C(O)OR 7 , and (CH 2 )SO 2 NR 7 R 8 ;

R 7 and R 8 are, independently, hydrogen, C 1 -C 8 alkyl, C 2 -C 8 alkenyl, C 2 -C 8 alkynyl, arylalkyl, cycloalkyl, heterocycloalkyl, aryl, heteroaryl, or heterarylalkyl; or

R 7 and R 8 , when attached to the same nitrogen atom, taken together with the nitrogen to which they are attached, may form a heterocyclic ring containing from 3-8 ring members, up to four of which members are optionally heteroatoms independently selected from oxygen, sulfur, S(O), S(O) 2 , and nitrogen, provided, however, that there is at least one carbon atom in the heterocyclic ring and that if there are two or more ring oxygen atoms, the ring oxygen atoms are not adjacent to one another, wherein the heterocyclic group is unsubstituted or substituted with one, two or three groups independently selected from halogen, hydroxy, hydroxyalkyl, lower alkyl, lower alkoxy, alkoxycarbonyl, alkylcarbonyl, alkylcarbonylamino, aminoalkyl, aminoalkylcarbonyl, trifluoromethyl, trifluoromethylalkyl, trifluoromethylalkylaminoalkyl, amino, nitrile, mono- or dialkylamino, N-hydroxyacetamido, aryl, heteroaryl, carboxyalkyl.

2. The method according to claim 1 wherein the mammal is human.

3. The method according to claim 1 , wherein the compound is selected from the group consisting of:

6-Acetyl-8-cyclopentyl-2-[5-(3,5-dimethyl-piperazin-1-yl )-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one-,

6-Acetyl-8-cyclopentyl-2-[5-(3,3-dimethyl-piperazin-1-yl )-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-[5-(4-methyl-piperazin-1-yl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-[5-(3-amino-pyrrolidin-1-yl)-pyridin-2-ylamino]-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-(5-morpholin-4-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

2-{5-[Bis-(2-methoxy-ethyl)-amino]-pyridin-2-ylamino}-6-bromo-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-(5-morpholin-4-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-{5-[bis-(2-methoxy-ethyl )-amino]-pyridin-2-ylamino}-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

4-[6-(8-Cyclopentyl-6-iodo-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-piperazine-1-carboxylic acid tert-butyl ester,

8-Cyclopentyl-6-iodo-5-methyl-2-(5-piperazin-1 -yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

2-{5-[Bis-(2-methoxy-ethyl)-amino]-pyridin-2-ylamino}-6-bromo-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-{5-[bis-(2-methoxy-ethyl )-amino]-pyridin-2-ylamino}-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-(pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-[5-(4-methyl-piperazin-1-yl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

8-Cyclopentyl-6-(1-ethoxy-vinyl)-5-methyl-2-[5-(4-methyl-piperazin-1-yl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

(1-{6-[8-Cyclopentyl-6-(1-ethoxy-vinyl )-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino]-pyridin-3-yl}-pyrrolidin-3-yl)-carbamic acid tert-butyl ester,

6-Acetyl-8-cyclopentyl-2-(4-hydroxy-3,4,5,6-tetrahydro-2H-[1,3′]bipyridinyl-6′-ylamino)-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

4-[6-(6-Bromo-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-azepane-1-carboxylic acid tert-butyl ester,

6-Bromo-8-cyclopentyl-2-(5-[1,4]diazepan-1 -yl-pyridin-2-ylamino)-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

4-{6-[8-Cyclopentyl-6-(1-ethoxy-vinyl)-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino]-pyridin-3-yl}-[1,4]diazepane-1 -carboxylic acid tert-butyl ester,

6-Acetyl-8-cyclopentyl-2-(5-[1,4]diazepan-1-yl-pyridin-2-ylamino)-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-(pyridin-2-ylamino)-8H-pyrido[2,3-d]pyriminin-7-one,

4-[6-(8-Cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-piperazine-1 -carboxylic acid tert-butyl ester,

8-Cyclopentyl-5-methyl-2-(5-piperazin-4-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

4-[6-(6-Bromo-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-2,2-dimethyl-piperazine-1-carboxylic acid tert-butyl ester,

6-Bromo-8-cyclopentyl-2-[5-(3,3-dimethyl-piperazin-1-yl)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3d]pyrimidin-7-one,

4-{6-[8-Cyclopentyl-6-(1-ethoxy-vinyl)-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino]-pyridin-3-yl}-2,2-dimethyl-piperazine-1-carboxylic acid tert-butyl ester,

4-[6-(6-Bromo-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-2,6-dimethyl-piperazine-1-carboxylic acid tert-butyl ester,

6-Bromo-8-cyclopentyl-2-[5-(3,5-dimethyl-piperazin-1-yl)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

4-{6-[8-Cyclopentyl-6-(1-ethoxy-vinyl)-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino]-pyridin-3-yl}-2,6-dimethyl-piperazine-1-carboxylic acid tert-butyl ester,

8-Cyclopentyl-6-(1-ethoxy-vinyl)-5-methyl-2-(5-morpholin-4-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-(3,4,5,6-tetrahydro-2H-[1,3′]bipyridinyl-6′-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

8-Cyclopentyl-6-(1-ethoxy-vinyl)-5-methyl-2-(3,4,5,6-tetrahydro-2H-[1,3′]bipyridinyl-6′-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-(3,4,5,6-tetrahydro-2 H-[1,3′]bipyridinyl-6′-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-2-[5-(2,6-dimethyl-morpholin-4-yl)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

8-Cyclopentyl-2-[5-(2,6-dimethyl-morpholin-4-yl)-pyridin-2-ylamino]-6-(1-ethoxy-vinyl)-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(2,6-dimethyl-morpholin-4-yl)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

8-Cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-6-propionyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-(5-piperizin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

2-[5-(4-tert-Butoxycarbonyl-piperazin-1 -yl)-pyridin-2-ylamino]-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidine-6-carboxylic acid ethyl ester,

6-Acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-(pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(3-ethylamino-pyrrolidin-1-yl )-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-(5-pyrrolidin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-{5-[3-(1-amino-1-methyl-ethyl)-pyrrolidin-1-yl]-pyridin-2-ylamino}-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

1-[6-(6-Acetyl-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-pyrrolidine-2-carboxylic acid,

6-Acetyl-8-cyclopentyl-2-[5-(4-diethylamino-butylamino)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-(3,4,5,6-tetrahydro-2H-[1 ,3′]bipyridinyl-6′-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-2-(5-diethylamino-pyridin-2-ylamino)-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

2-{5-[Bis-(2-hydroxy-ethyl )-amino]-pyridin-2-ylamino}-6-bromo-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

2-[5-(2-Amino-ethylamino)-pyridin-2-ylamino]-6-bromo-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-2-(5-dimethylamino-pyridin-2-ylamino)-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

N-[6-(6-Bromo-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-N-methyl-acetamide,

6-Bromo-8-cyclopentyl-2-[5-(2-methoxy-ethoxy)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-2-[5-(2-methoxy-ethoxymethyl)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-2-[5-(2-diethylamino-ethoxy)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-(5-pyrrolidin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-(6-methyl-5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-(3,4,5,6-tetrahydro-2 H-[1,3′]bipyridinyl-6′-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-(5-diethylamino-pyridin-2-ylamino)-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-{5-[bis-(2-hydroxy-ethyl )-amino]-pyridin-2-ylamino}-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-[5-(2-amino-ethylamino)-pyridin-2-ylamino]-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-(5-dimethylamino-pyridin-2-ylamino)-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

N-[6-(6-Acetyl-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-N-methyl-acetamide,

6-Acetyl-8-cyclopentyl-2-[5-(2-methoxy-ethoxy)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(2-methoxy-ethoxymethyl )-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(2-diethylamino-ethoxy)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-(5-pyrrolidin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-(6-methyl-5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(2-methoxy-ethoxy)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(2-methoxy-ethylamino)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-(5-azetidin-1-yl-pyridin-2-ylamino)-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-(5-azepan-1-yl-pyridin-2-ylamino)-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

N-[6-(6-Acetyl-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-acetamide,

6-Acetyl-8-cyclopentyl-5-methyl-2-(5-phenylamino-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(4-fluoro-benzylamino)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

N-[6-(6-Acetyl-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2 3-d]pyrimidin-2-ylamino)-pyridin-3-yl]-methanesulfonamide,

6-Acetyl-8-cyclopentyl-2-(5-methanesulfonyl-pyridin-2-ylamino)-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-(5-phenyl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-[5-(piperazine-1-carbonyl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-2-[5-(3,5-dimethyl-piperazine-1-carbonyl)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

2-[5-(3-Amino-pyrrolidine-1-carbonyl)-pyridin-2-ylamino]-6-bromo-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-[5-(morpholine-4-carbonyl )-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-[5-(piperazine-1-carbonyl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(3,5-dimethyl-piperazine-1-carbonyl )-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-[5-(3-amino-pyrrolidine-1-carbonyl)-pyridin-2-ylamino]-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-[5-(morpholine-4-carbonyl )-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-[5-(piperazine-1-sulfonyl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-5-methyl-2-[5-(morpholine-4-sulfonyl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

2-[5-(3-Amino-pyrrolidine-1-sulfonyl)-pyridin-2-ylamino]-6-bromo-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Bromo-8-cyclopentyl-2-[5-(3,5-dimethyl-piperazine-1-sulfonyl)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-[5-(piperazine-1-sulfonyl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-[5-(morpholine-4-sulfonyl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-[5-(3-amino-pyrrolidine-1-sulfonyl)-pyridin-2-ylamino]-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(3,5-dimethyl-piperazine-1-sulfonyl)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-5-methyl-2-([1,6]naphthyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-8-cyclopentyl-2-[5-(1,1 -dioxo-1|6-thiomorpholin-4-yl)-pyridin-2-ylamino]-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

8-Cyclopentyl-6-hydroxymethyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-2-(3-chloro-5-piperazin-1-yl-pyridin-2-ylamino)-8-cyclopentyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one,

4-[6-Acetyl-5-methyl-7-oxo-2-(pyridin-2-ylamino)-7H-pyrido[2,3-d]pyrimidin-8-yl]-cyclohexanecarboxylic acid,

4-[6-Acetyl-2-(5-dimethylamino-pyridin-2-ylamino)-5-methyl-7-oxo-7H-pyrido[2,3-d]pyrimidin-8-yl]-cyclohexanecarboxylic acid,

6-Bromo-8-cyclopentyl-5-methyl-2-[5-(piperazine-1-sulfonyl)-pyridin-2-ylamino]-8H-pyrido[2,3-d]pyrimidin-7-one,

6-Acetyl-5-methyl-2-(5-methyl-pyridin-2-ylamino)-8-piperidin-4-yl-8H-pyrido[2,3-d]pyrimidin-7-one, and

6-Acetyl-2-[5-(3,4-dihydroxy-pyrrolidin-1-yl)-pyridin-2-ylamino]-8-methoxymethyl-5-methyl-8H-pyrido[2,3-d]pyrimidin-7-one;

and pharmaceutically acceptable salts thereof.

4. The method according to claim 1 , wherein the compound is selected from the group consisting of:

6-Bromo-8-cyclopentyl-5-methyl-2-(5-piperizin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one,

2-[5-(4-tert-Butoxycarbonyl-piperazin-1-yl)-pyridin-2-ylamino]-8-cyclopentyl-5-methyl-7-oxo-7,8-dihydro-pyrido[2,3-d]pyrimidine-6-carboxylic acid ethyl ester,

6-Acetyl-8-cyclopentyl-5-methyl-2-(5-piperazin-1-yl-pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one, and

6-Bromo-8-cyclopentyl-5-methyl-2-(pyridin-2-ylamino)-8H-pyrido[2,3-d]pyrimidin-7-one;

and pharmaceutically acceptable salts thereof.