Prodrugs containing an aromatic amine connected by an amido bond to a linker

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 L1 represented by formula (I):
• wherein:
• the dashed line indicates the attachment of L1 to an aromatic amino group of D by forming an amide bond;
• X1 is C(R1R1a) or a cyclic fragment selected from the group consisting of C3-7 cycloalkyl, 4 to 7 membered heterocyclyl, phenyl, naphthyl, indenyl, indanyl, tetralinyl, and 9 to 11 membered heterobicyclyl, wherein:
• in case X1 is a cyclic fragment, said cyclic fragment is incorporated into L1 via two adjacent ring atoms and the ring atom of X1, which is adjacent to the carbon atom of the amide bond, is also a carbon atom;
• X2 is a chemical bond or selected from C(R3R3a), N(R3), O, C(R3R3a)—C(R4R4a), C(R3R3a)—N(R4), N(R3)—C(R4R4a), C(R3R3a)—O, or O—C(R3R3a), wherein:
• in case X1 is a cyclic fragment, X2 is a chemical bond, C(R3R3a), N(R3), or O;
• optionally, in case X1 is a cyclic fragment and X2 is C(R3R3a), the order of the X1 fragment and the X2 fragment within L1 may be changed and the cyclic fragment is incorporated into L1 via two adjacent ring atoms;
• R1, R3, and R4 are independently selected from the group consisting of H, C1-4 alkyl, and —N(R5R5a);
• R1a, R2, R3a, R4a, and R5a are independently selected from the group consisting of H and C1-4 alkyl;
• R5 is C(O)R6;
• and
• R6 is C1-4 alkyl;
• and
• optionally, one of the pairs R1a/R4a, R3a/R4a or R1a/R3a form a chemical bond;
• and
• ii) a moiety L2, which is a chemical bond or a spacer, where L2 is bound to a polymeric carrier group Z;
• wherein L1 is substituted with one to four L2 moieties, provided that the hydrogen marked with the asterisk in formula (I) is not replaced by L2;
• and
• wherein, optionally, L is further substituted.