The invention relates to sulfonamide derivatives, to their use in medicine, to 5 compositions containing them, to processes for their preparation and to intermediates used in such processes. More particularly the invention relates to a new sulfonamide Nav1.7 inhibitors of formula (I):10 X NH O S O O R1 R2 R5 R4 R3 Het1 (I) or a pharmaceutically acceptable salt thereof, wherein X, Het1, R1, R2, R3, R4 and R5 are as defined in the description. 15 Nav 1.7 inhibitors are potentially useful in the treatment of a wide range of disorders, particularly pain.