Pharmaceutical compositions for inhalation comprising compounds of formula (I) are useful in the treatment of diseases where enhanced M3 receptor activation is implicated, such as respiritory tract diseases: wherein (i) R 1 is C 1 -C 6 -alkyl or hydrogen； and R 2 is hydrogen or a group -R 7 , -Z-Y-R 7 , -Z-NR 9 R 10 ； -Z-CO-NR 9 R 10 , -Z-NR 9 -C(O)O-R 7 , or -Z-C(O)-R 7 ； and R 3 is a lone pair, or C 1 -C 6 -alkyl； or (ii) R 1 and R 3 together with the nitrogen to which they are attached form a heterocycloalkyl ring, and R 2 is a lone pair or a group -R 7 , -Z-Y-R 7 , -Z-NR 9 R 10 , -Z-CO-NR 9 R 10 , -Z-NR 9 -C(O)O-R 7 ； or； -Z-C(O)-R 7 ； or (iii) R 1 and R 2 together with the nitrogen to which they are attached form a heterocycloalkyl ring, said ring being substituted by a group -Y-R 7 , -Z-Y-R 7 , -Z-NR 9 R 10 ； -Z-CO-NR 9 R 10 ； -Z-NR 9 -C(O)OR 7 ； or； -Z-C(O)-R 7 ； and R 3 is a lone pair, or C 1 -C 6 -alkyl； R 4 and R 5 are independently selected from the group consisting of aryl, aryl-fused-heterocycloalkyl, heteroaryl, C 1 -C 6 -alkyl, cycloalkyl； R 6 is -OH, C 1 -C 6 -alkyl, C 1 -C 6 -alkoxy, hydroxy-C 1 -C 6 -alkyl, nitrile, a group CONR 8 2 or a hydrogen atom； A is an oxygen or a sulfur atom； X is an alkylene, alkenylene or alkynylene group； R 7 is an C 1 -C 6 -alkyl, aryl, aryl-fused-cycloalkyl, aryl-fused-heterocycloalkyl, heteroaryl, aryl(C 1 -C 8 -alkyl)-, heteroaryl(C 1 -C 8 -alkyl)-, cycloalkyl or heterocycloalkyl group； R 8 is C 1 -C 6 -alkyl or a hydrogen atom； Z is a C 1 -C 16 -alkylene, C 2 -C 16 -alkenylene or C 2 -C 16 -alkynylene group； Y is a bond or oxygen atom； R 9 and R 10 are independently a hydrogen atom, C 1 -C 6 -alkyl, aryl, aryl-fused-heterocycloalkyl, aryl-fused-cycloalkyl, heteroaryl, aryl(C 1 -C 6 -alkyl)-, or heteroaryl(C 1 -C 6 -alkyl)- group； or R 9 and R 10 together with the nitrogen atom to which they are attached form a heterocyclic ring of 4-8 atoms, opti
