Abstract: According to the invention there is provided a compound of formula (I) wherein: A represents C(?N—W-D) or S; B represents S or C(—NH—W-D); when: A represents C(?N—W-D) and B represents S then the bond between B and the NH atom is a single bond; or A represents S and B represents C(—NH—W-D) then the bond between B and the NH atom is a double bond; X represents -Q-[CRxRy]n—; W represents —[CRxRy]m— or —C(O)—[CRxRy]p—; Q represents a bond, —N(Ra)—; —S—, or —O—; A1 to A5 respectively represent C(R1), C(R2), C(R3), C(R4) and C(R5), or, alternatively, up to two of A1 to A5 may independently represent N; D represents phenyl, pyridyl or pyrimidinyl optionally substituted by one or more R6 groups, which compounds are useful in the treatment of cancer.