The present invention relates to compounds of Formula (Ia) or (Ib), the N-oxide forms, pharmaceutically acceptable addition salts, quaternary amines, stereoisomers, tautomers, racemics, metabolites, prodrugs, hydrates, or solvates thereof, wherein Y1, m, n, R1； X1； X2； R2； X3； X4； R3； and R4 have the meaning defined in the claims. The present invention also relates to processes for preparing said compounds, pharmaceutical compositions containing them and their use in therapy. The invention particularly relates to compounds that are kinase inhibitors useful for the treatment of disease states mediated by kinase, especially PLK4, in particular such compounds that are useful in the treatment of pathological processes which involve an aberrant cellular proliferation, such as tumor growth, rheumatoid arthritis, restenosis and atherosclerosis.
