A compound for use in the treatment of a lysosomal storage disease, wherein the compound is represented by the following structural formula, or a pharmaceutically acceptable salt thereof, wherein: n is 1 or 2; m is 0 or 1; p is 1; t is 0; y is 1; z is 0 or 1; E is O; X 1 is CR 1 when m is 1 or N when m is 0; X 2 is O, -NH, -CH 2 - or -NR 2; X 3 is O, -NH, -CH 2 -, - CH(C 1 -C 6) alkyl or -NR 3; X 4 is CR 4 R 5, or CH 2 CR 4 R 5; X 5 is a direct bond, O, or (C 1 -C 6)alkyloxy, R 1 is H, CN, (C 1 -C 6)alkylcarbonyl, or (C 1 -C 6)alkyl; R 2 and R 3 are each independently -H, or optionally when X 2 is -NR 2 and X 3 is -NR 3, R 2 and R 3 may be taken together with the nitrogen atoms to which they are attached form a non-aromatic heterocyclic ring; R 4 and R 5 are independently selected from H, (C 1 -C 6)alkyl, or taken together with the carbon to which they are attached to form a spiro (C 3 -C 10)cycloalkyl ring or spiro (C 3 -C 10)cycloalkoxy ring; R 6 is -H, -CN, or (C 1 -C 6)alkyl, A 1 is (C 6 -C 12)aryl, (C 2 -C 9)heteroaryl, or benzo(C 2 -C 9)heterocycloalkyl optionally substituted with one or more substituents selected from the group consisting of halo, (C 1 -C 6)alkyl; (C 1 -C 6)alkenyl, and (C 1 -C 6)alkoxy; A 2 is H, (C 3 -C 10)cycloalkyl, (C 6 -C 12)aryl, or (C 2 -C 9)heteroaryl, optionally substituted with one or more substituents selected from the group consisting of halo, (C 1 -C 6)alkyl optionally substituted by one to three halo; CN, and (C 1 -C 6)alkyloxy optionally substituted by one to three halo; with the proviso that when n is 1; t is 0; y is 1; z is 1; X 2 is NH; E is O; X 3 is NH; A 2 is H and X 5 is a direct bond; A 1 is not unsubstituted phenyl, halophenyl or isopropenyl phenyl; with the proviso that when n is 1; t is 0; y is 1; z is 1; X 2 is O; E is O; X 3 is NH; A 1 is (C 6 -C 12)aryl and X 5 is a direct bond; A 2 is H and R 4 is H then R 5 is not cyclohexyl; and with the proviso that when n is 1; t is 0; y is 1; z is 1; X 2 is NH; E is O; X 3 is CH 2; R 4 and R 5 are both hydrogen; A 2 is H and X 5 is a direct bond; then A 1 is not unsubstituted phenyl. n is 1 or 2; m is 0 or 1; p is 1; t is 0; y is 1; z is 0 or 1; E is O; X 1 is CR 1 when m is 1 or N when m is 0; X 2 is O, -NH, -CH 2 - or -NR 2; X 3 is O, -NH, -CH 2 -, - CH(C 1 -C 6) alkyl or -NR 3; X 4 is CR 4 R 5, or CH 2 CR 4 R 5; X 5 is a direct bond, O, or (C 1 -C 6)alkyloxy, R 1 is H, CN, (C 1 -C 6)alkylcarbonyl, or (C 1 -C 6)alkyl; R 2 and R 3 are each independently -H, or optionally when X 2 is -NR 2 and X 3 is -NR 3, R 2 and R 3 may be taken together with the nitrogen atoms to which they are attached form a non-aromatic heterocyclic ring; R 4 and R 5 are independently selected from H, (C 1 -C 6)alkyl, or taken together with the carbon to which they are attached to form a spiro (C 3 -C 10)cycloalkyl ring or spiro (C 3 -C 10)cycloalkoxy ring; R 6 is -H, -CN, or (C 1 -C 6)alkyl, A 1 is (C 6 -C 12)aryl, (C 2 -C 9)heteroaryl, or benzo(C 2 -C 9)heterocycloalkyl optionally substituted with one or more substituents selected from the group consisting of halo, (C 1 -C 6)alkyl; (C 1 -C 6)alkenyl, and (C 1 -C 6)alkoxy; A 2 is H, (C 3 -C 10)cycloalkyl, (C 6 -C 12)aryl, or (C 2 -C 9)heteroaryl, optionally substituted with one or more substituents selected from the group consisting of halo, (C 1 -C 6)alkyl optionally substituted by one to three halo; CN, and (C 1 -C 6)alkyloxy optionally substituted by one to three halo; with the proviso that when n is 1; t is 0; y is 1; z is 1; X 2 is NH; E is O; X 3 is NH; A 2 is H and X 5 is a direct bond; A 1 is not unsubstituted phenyl, halophenyl or isopropenyl phenyl; with the proviso that when n is 1; t is 0; y is 1; z is 1; X 2 is O; E is O; X 3 is NH; A 1 is (C 6 -C 12)aryl and X 5 is a direct bond; A 2 is H and R 4 is H then R 5 is not cyclohexyl; and with the proviso that when n is 1; t is 0; y is 1; z is 1; X 2 is NH; E is O; X 3 is CH 2; R 4 and R 5 are both hydrogen; A 2 is H and X 5 is a direct bond; then A 1 is not unsubstituted phenyl.