Pyrazole derivatives useful for the treatment of gynaecological diseases

Compounds of formula (I), or a pharmaceutically acceptable derivative thereof, wherein R1 and R3 independently represent H, C1-6alkyl, C3-8cycloalkyl, or halogen; R2 represents C1-6alkyl, CF3 or aryl; a represents 1 or 2; R4, R5, R7 and R8 independently represent H, C1-6alkyl, C1-6alkyloxy, CN or halogen, or R4 and R5, or R7 and R8, together with the ring to which they are attached form an aryl or heterocyclic fused ring system; X represents C or N; Y represents CH2 or O; R6 represents H, CN or halo provided that, when X represents N, R6 is absent. The compounds are useful for treating endometriosis, uterine fibroids (leiomyomata), menorrhagia, adenomyosis, primary and secondary dysmenorrhoea (including symptoms of dyspareunia, dyschexia and chronic pelvic pain), or chronic pelvic pain syndrome.