There is provided compounds of formula I,
wherein X
1
, R
1
, R
2
, R
3
, R
4
, R
5
and R
6
have meanings given in the description, and pharmaceutically-acceptable salts thereof, which compounds are useful in the treatment of diseases in which inhibition of the activity of a member of the MAPEG family is desired and/or required, and particularly in the treatment of inflammation.