Therapeutic quinazoline derivatives

A compound of formula (I) or a salt, ester, amide or prodrug thereof; where X is O, or S, S(O), S(O)2 or NR6 where R6 is hydrogen of C1-6alkyl; R5 is an optionally substituted 6-membered aromatic ring containing at least one nitrogen atom, and R1, R2, R3, R4 are independently selected from halogeno, cyano, nitro, C1-3alkylsulphanyl, -N(OH)R7- (wherein R7 is hydrogen, or C1-3alkyl), or R9X1- (wherein X1 represents a direct bond, -O-, -CH2-, -OC(O), -C(O)-, -S-, -SO-, -SO2-, -NR10C(O)-, -C(O)NR11-, -SO2NR12-, -NR13SO2- or NR14- (wherein R10, R11, R12, R13 and R14 each independently represents hydrogen, C1-3alkyl or C1-3alkoxyC2-3alkyl), and R9 is hydrogen, optionally substituted hydrocarbyl, optionally substituted heterocyclyl or optionally substituted alkoxy; provided that at least one of R2 or R3 is other than hydrogen. These compounds inhibit aurora 2 kinase and are useful in the preparation of medicaments for the treatment of proliferative disease such as cancer.