A first aspect of the invention relates to a compound of formula (I), or a pharmaceutically acceptable salt or ester thereof, wherein: B is an aryl or heteroaryl group optionally substituted by one or more R10 groups； and * X is selected from 0, (CR11 R12 ) p and (CR11 R12 ) p CO. Said compounds are capable of inhibiting PAICS and are useful in the treatment of proliferative disorders. Further aspects relate to pharmaceutical compositions, therapeutic uses and process for preparing compounds of formula (I).
