The invention relates to a compound of formula (1); wherein: R.sup.1 and R.sup.2 each independently represent a C.sub.1-6alkyl, C.sub.3-6 alkenyl, C.sub.3-6 cycloalkyl C.sub.1-3 alkyl or C.sub.3-6 cycloalkyl; each of which may be optionally substituted by 1 to 3 halogen atoms; R.sup.3 is isoxyzolidin-2-ylcarbonyl or tetrahydroisoxazin-2-ylcarbonyl wherein each ring is optionally substituted by one hydroxy group; Q is CO-- or C(R.sup.4)(R.sup.5)-(wherein R.sup.4 is a hydrogen atom or C.sub.1-4alkyl and R.sup.5 is a hydrogen atom or hydroxy group); Ar is a 5- to 10-membered aromatic ring system wherein up to 4 ring atoms may be heteroatoms independently selected from nitrogen, oxygen and sulphur, the ring system being optionally substituted by one or more substituents as defined in the specification. It also relates to methods of preparing, pharmaceutical compositions containing and methods of using the compound of the formula (1), particularly in the modulation of autoimmune disease ##STR00001##