Compounds of formula (I) are inhibitors of matrix metalloproteinases, and areof use in the treatment of, for example fibrotic disease, multiple sclerosis,emphysemia, bronchitis and asthma: formula (I) wherein Ar represents anoptionally substituted aryl, heteroaryl, C3-C8 cycloalkyl or heterocycloakylgroup； R represents hydrogen or C1-C6 alkyl, or C3-C6 cycloalkyl； Alkrepresents a divalent C1-C5 alkylene or C2-C5 alkenylene radical； and R1 andR2 taken together with the nitrogen atom to which they are attached form afirst heterocycloalkyl ring which is optionally fused to a second C3-C8cycloalkyl or heterocycloalkyl ring, the said first and second rings beingoptionally substituted by at least one group of formula (II): formula (II)wherein m, p and n are independently 0 or 1； Z represents, hydrogen, or anoptionally substituted carbocyclic or heterocyclic ring of from 5 to 7 ringatoms which is optionally fused to another optionally substituted carbocyclicor heterocyclic ring of from 5 to 7 ring atoms； Alk1 and Alk2 independentlyrepresent optionally substituted divalent C1-C3 alkylene radicals； Xrepresents -0-, -S-, -S(O)-, -S(O2)-, -C(=O)-, -NH-, -NR3-, -S(O2)NH-, -S(O2)NR3-, -NHS(O2)-, or -NR3S(O2)-, where R3 is C1-C3 alkyl.
