Compounds of formula I are p38 inhibitors: ##STR1##

or a pharmaceutically acceptable salt thereof,

wherein

• R¹ is hydrogen or alkyl;
• R² alkyl, haloalkyl, aryl, aralkyl, heteroaryl, heteroaralkyl, cycloalkyl, cycloalkylalkyl, heteroalkylsubstituted cycloalkyl, heterosubstituted cycloalkyl, heteroalkyl, cyanoalkyl, heterocyclyl, heterocyclylalkyl, or —Y¹—C(O)—Y²—R¹¹ (where Y¹ and Y² are independently either absent or an alkylene group and R¹¹ is hydrogen, alkyl, haloalkyl, hydroxy, alkoxy, amino, monoalkylamino or dialkylamino);
• R³ is hydrogen, alkyl, cycloalkyl, cycloalkylalkyl, heterosubstituted cycloalkyl, heterocyclyl, aryl, aralkyl, haloalkyl, heteroalkyl, cyanoalkyl, -alkylene-C(O)—R⁴ (where R⁴ is hydrogen, alkyl, hydroxy, alkoxy, amino, monoalkylamino or dialkylamino), or acyl;
• Ar¹ is aryl;
• X¹ is O, NR⁵ or S, where R⁵ is hydrogen or alkyl; and
• X² is a bond, O, NR⁶, S or CH₂, where R⁶ is hydrogen or alkyl.