The present invention relates to a prodrug or a pharmaceutically acceptable salt thereof comprising a drug linker conjugate D-L, wherein -D is an amine containing biologically active moiety； and -L is a non-biologically active linker moiety -L 1 represented by formula (I), wherein the dashed line indicates the attachment to the amine of the biologically active moiety and wherein R 1 , R 1a , R 2 , R 2a , R 3 , R 3a , X, X 1 , X 2 , X 3 have the meaning as indicated in the description and the claims and wherein L 1 is substituted with one to four groups L 2 -Z and optionally further substituted, provided that the hydrogen marked with the asterisk in formula (I) is not replaced by a substituent； wherein L 2 is a single chemical bond or a spacer； and Z is a carrier group and wherein D-H is a polypeptide selected from the group of polypeptides consisting of exendins, glucagon, glucagon-like peptides and insulins. The invention also relates pharmaceutical composition comprising said prodrugs and their use as medicaments.
