Inhibitors of polo-like kinase

A compound having a structure according to Formula (I):

• or a salt or solvate thereof, wherein:
• X is C or N and the dashed line represents a single or double bond;
• A is a ring selected from the group consisting of phenyl, pyridine, pyrimidine, pyrazine, pyridazine, pyrrole, pyrazole, imidazole, thiazole, isothiazole, isoxazole, triazole, thiadiazole, benzimidazole, indole, pyrrolo[2,3-b]pyridine, quinoline, pyrrolidine, piperidine, piperazine, and dihydro-imidazole;
• R1 is methyl (e.g. —CD3 or —CH3, more preferably —CH3);
• R2 is hydrogen, methyl (e.g. —CD3 or —CH3), ethyl (e.g. —CD2CD3 or —CH2CH3), —CH2-cyclopropyl, or —CH2CF3;
• R3 is methyl (e.g. —CD3 or —CH3), ethyl (e.g. —CD2CD3 or —CH2CH3), —CH2-cyclopropyl, or —CH2CF3;
• or R2 and R3, together with the carbon atom to which they are attached, are optionally joined to form cyclobutyl;
• R4 is selected from the group consisting of —NH2, —NHCH3, —NHcyclopropyl, pyrrolidine, —CH2-cyclopropyl, —CH(CH3)-cyclopropyl, cyclopropyl, cyclobutyl optionally substituted with 1 or 2 fluoro, cyclopentyl optionally substituted with 1 or 2 fluoro, isopropyl (e.g. —CH(CH3)2 or —CD(CD3)2), —CH2CH2CF3, tetrahydropyran, tetrahydrofuran, oxetane, phenyl optionally substituted with 1 or 2 substituents R7, pyrazole optionally substituted with 1 substituent R8, and pyrimidine;
• or R4 and R3, together with the atoms to which they are attached, are optionally joined to form a substituted or unsubstituted 5- to 7-membered heterocyclic ring selected from the group consisting of
• and
• wherein
• represents the core ring of Formula I, i.e. the N attached to R4 and the C attached to R3;
• or R4, R2 and R3, together with the atoms to which they are attached, are optionally joined to form a substituted or unsubstituted 7-membered heterocyclic ring selected from the group consisting of
• wherein
• represents the core ring of Formula I, i.e. the N attached to R4 and the C attached to R3/R2;
• R5 is hydrogen, —Br, —CN, —CH3, —CH2CN, —CH2CH2NH2, —OH, —O−, ═O, —OCH3, —Obenzyl, —C(O)OH, —C(O)OCH3, —C(O)OCH2CH3, —C(O)NH2, —C(O)NHCH3, —C(O)N(CH3)2,
• —NH2, ═NH, —NHCH3, —N(CH3)2, —NHS(O)2CH3, —S(O)2CH3, phenyl, thiazole, pyridine or pyrazine;
• R6 is hydrogen, —Cl, —Br, —CH3, —CF3, —CH2NH2, —NH2, —CH2NHC(O)OCH3, —CH2NHC(O)CH3, —CH2NHC(O)phenyl, —CH2NHS(O)2CH3, —CH2NHS(O)2-phenyl, —NHC(O)CH3, —NHC(O)OCH3, —NHC(O)phenyl, —NHS(O)2CH3, —NHS(O)2-phenyl, —CCHphenyl, cyclopropyl, cyclopentenyl, benzyl, phenyl optionally sub with 1, 2 or 3 substituents R9, pyridine optionally substituted with 1 fluoro, pyrimidine, pyrazine, pyridazine, pyrazole, thiazole, oxazole, thiophene optionally substituted with 1 chloro, pyrrolidine, oxazolidinone, pyrrolidinone, dihydropyran, tetrahydropyran, morpholine, 4-methyl-piperazine, pyrrolidine-dione, pyridinone, isoquinoline, or quinoline;
• R7 at each occurrence is independently —C(O)NH2, fluoro, chloro, cyano, pyrazole, triazole, pyridine or pyrimidine;
• R8 is methyl or 2-(trimethylsilyl)ethoxy)methyl, cyclopropyl, or —CH2-cyclopropyl;
• and
• R9 at each occurrence is independently selected from the group consisting of fluoro, chloro, bromo, —S(O)2CH3, —OCF3, —CF3, —CN, pyridine, triazole, and pyrazole.