A prodrug or a pharmaceutically acceptable salt thereof comprising a drug linker conjugate D-L, wherein D is an aromatic amine containing biologically active moiety; and L is a non-biologically active linker containing i) a moiety L 1 represented by formula, wherein the dashed line indicates the attachment of L 1 to an aromatic amino group of D by forming an amide bond; X 1 is C(R 1 R 1a) or a cyclic fragment selected from the group consisting of C 3-7 cycloalkyl, 4 to 7 membered heterocyclyl, phenyl, naphthyl, indenyl, indanyl, tetralinyl and 9 to 11 membered heterobicyclyl; wherein in case X 1 is a cyclic fragment, said cyclic fragment is incorporated into L 1 via two adjacent ring atoms and the ring atom of X 1, which is adjacent to the carbon atom of the amide bond, is also a carbon atom; X 2 is a chemical bond or selected from the group consisting of C(R 3 R 3a), N(R 3), O C(R 3 R 3a)-C(R 4 R 4a), C(R 3 R 3a)-N(R 4), N(R 3)-C(R 4 R 4a), C(R 3 R 3a)-O and O-C(R 3 R 3a); wherein in case X 1 is a cyclic fragment, X 2 is a chemical bond, C(R 3 R 3a), N(R 3) or O; optionally, in case X 1 is a cyclic fragment and X 2 is C(R 3 R 3a), the order of the X 1 fragment and the X 2 fragment within L 1 may be changed and the cyclic fragment is incorporated into L 1 via two adjacent ring atoms; R 1, R 3 and R 4 are independently selected from the group consisting of H, C 1-4 alkyl and -N(R 5 R 5a); R 1a, R 2, R 3a, R 4a and R 5a are independently selected from the group consisting of H and C 1-4 alkyl; R 5 is C R 6; R 6 is C 1-4 alkyl; optionally, one of the pairs R 1a /R 4a, R 3a /R 4a or R 1a /R 3a form a chemical bond; and ii) a moiety L 2, which is a chemical bond or a spacer, and L 2 is bound to a polymeric carrier group Z; wherein L 1 is substituted with one L 2 and the carrier group Z is a biodegradable polyethylene glycol based water-insoluble hydrogel, provided that the hydrogen marked with the asterisk in formula is not replaced by L 2; and optionally, L is further substituted. i) a moiety L 1 represented by formula, wherein the dashed line indicates the attachment of L 1 to an aromatic amino group of D by forming an amide bond; X 1 is C(R 1 R 1a) or a cyclic fragment selected from the group consisting of C 3-7 cycloalkyl, 4 to 7 membered heterocyclyl, phenyl, naphthyl, indenyl, indanyl, tetralinyl and 9 to 11 membered heterobicyclyl; wherein in case X 1 is a cyclic fragment, said cyclic fragment is incorporated into L 1 via two adjacent ring atoms and the ring atom of X 1, which is adjacent to the carbon atom of the amide bond, is also a carbon atom; X 2 is a chemical bond or selected from the group consisting of C(R 3 R 3a), N(R 3), O C(R 3 R 3a)-C(R 4 R 4a), C(R 3 R 3a)-N(R 4), N(R 3)-C(R 4 R 4a), C(R 3 R 3a)-O and O-C(R 3 R 3a); wherein in case X 1 is a cyclic fragment, X 2 is a chemical bond, C(R 3 R 3a), N(R 3) or O; optionally, in case X 1 is a cyclic fragment and X 2 is C(R 3 R 3a), the order of the X 1 fragment and the X 2 fragment within L 1 may be changed and the cyclic fragment is incorporated into L 1 via two adjacent ring atoms; R 1, R 3 and R 4 are independently selected from the group consisting of H, C 1-4 alkyl and -N(R 5 R 5a); R 1a, R 2, R 3a, R 4a and R 5a are independently selected from the group consisting of H and C 1-4 alkyl; R 5 is C R 6; R 6 is C 1-4 alkyl; optionally, one of the pairs R 1a /R 4a, R 3a /R 4a or R 1a /R 3a form a chemical bond; and wherein the dashed line indicates the attachment of L 1 to an aromatic amino group of D by forming an amide bond; X 1 is C(R 1 R 1a) or a cyclic fragment selected from the group consisting of C 3-7 cycloalkyl, 4 to 7 membered heterocyclyl, phenyl, naphthyl, indenyl, indanyl, tetralinyl and 9 to 11 membered heterobicyclyl; wherein in case X 1 is a cyclic fragment, said cyclic fragment is incorporated into L 1 via two adjacent ring atoms and the ring atom of X 1, which is adjacent to the carbon atom of the amide bond, is also a carbon atom; X 2 is a chemical bond or selected from the group consisting of C(R 3 R 3a), N(R 3), O C(R 3 R 3a)-C(R 4 R 4a), C(R 3 R 3a)-N(R 4), N(R 3)-C(R 4 R 4a), C(R 3 R 3a)-O and O-C(R 3 R 3a); wherein in case X 1 is a cyclic fragment, X 2 is a chemical bond, C(R 3 R 3a), N(R 3) or O; optionally, in case X 1 is a cyclic fragment and X 2 is C(R 3 R 3a), the order of the X 1 fragment and the X 2 fragment within L 1 may be changed and the cyclic fragment is incorporated into L 1 via two adjacent ring atoms; R 1, R 3 and R 4 are independently selected from the group consisting of H, C 1-4 alkyl and -N(R 5 R 5a); R 1a, R 2, R 3a, R 4a and R 5a are independently selected from the group consisting of H and C 1-4 alkyl; R 5 is C R 6; R 6 is C 1-4 alkyl; optionally, one of the pairs R 1a /R 4a, R 3a /R 4a or R 1a /R 3a form a chemical bond; and ii) a moiety L 2, which is a chemical bond or a spacer, and L 2 is bound to a polymeric carrier group Z; wherein L 1 is substituted with one L 2 and the carrier group Z is a biodegradable polyethylene glycol based water-insoluble hydrogel, provided that the hydrogen marked with the asterisk in formula is not replaced by L 2; and optionally, L is further substituted.