The invention relates to a group of novel thieno-pyrrole compounds of formula (I) wherein: Rl, R2. R3, R4 M, and R5 are as defined in the specification, as inter alia, gonadotrophin releasing hormone antagonists. Novel compounds of formula (1) are also claimed. The invention also relates to pharmaceutical formulations of said compounds, methods of treatment using said compounds and to processes for the preparation of said compounds.