A polymeric human growth hormone (hGH) prodrug or a pharmaceutically acceptable salt thereof of formula (Ia) wherein -D is a hGH moiety connected to the rest of the molecule through an amine functional group; n is 0, 1, 2, 3, or 4; -X- is of formula wherein the dashed line marked with the asterisk indicates attachment to the -R 1; the unmarked dashed line indicates attachment to remainder of the prodrug; q5 is 1, 2, 3, 4, 5, 6, 7 or 8; =Y 1 is selected from the group consisting of =O and =S; -Y 2 - is selected from the group consisting of -O- and -S-; -Y 3 - is selected from the group consisting of -O- and -S-; -Y 4 - is selected from the group consisting of -O-, -NR 5 - and -C(R 6 R 6a)-; =Y 5 is selected from the group consisting of =O and =S; -R 1 is of formula (IIc): wherein p1, p2, p3, p4 are independently an integer ranging from 220 to 240; -R 3, -R 5, -R 6, -R 6a are independently of each other selected from the group consisting of -H, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 2,2-dimethylpropyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl and 3,3-dimethylpropyl; -R 4 is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 2,2-dimethylpropyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl and 3,3-dimethylpropyl; -W- is wherein the dashed lines indicate attachment to the rest of the molecule; -Nu is -N(R 7 R 7a); -Ar- is selected from the group consisting of wherein dashed lines indicate attachment to the rest of the prodrug, -Z 1 - is selected from the group consisting of -O-, -S- and -N(R 7)-, and -Z 2 - is -N(R 7)-; and -R 7, -R 7a are independently of each other selected from the group consisting of -H, C 1-6 alkyl, C 2-6 alkenyl and C 2-6 alkynyl. -D is a hGH moiety connected to the rest of the molecule through an amine functional group; n is 0, 1, 2, 3, or 4; -X- is of formula wherein the dashed line marked with the asterisk indicates attachment to the -R 1; the unmarked dashed line indicates attachment to remainder of the prodrug; q5 is 1, 2, 3, 4, 5, 6, 7 or 8; the dashed line marked with the asterisk indicates attachment to the -R 1; the unmarked dashed line indicates attachment to remainder of the prodrug; q5 is 1, 2, 3, 4, 5, 6, 7 or 8; =Y 1 is selected from the group consisting of =O and =S; -Y 2 - is selected from the group consisting of -O- and -S-; -Y 3 - is selected from the group consisting of -O- and -S-; -Y 4 - is selected from the group consisting of -O-, -NR 5 - and -C(R 6 R 6a)-; =Y 5 is selected from the group consisting of =O and =S; -R 1 is of formula (IIc): wherein p1, p2, p3, p4 are independently an integer ranging from 220 to 240; -R 3, -R 5, -R 6, -R 6a are independently of each other selected from the group consisting of -H, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 2,2-dimethylpropyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl and 3,3-dimethylpropyl; -R 4 is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 2,2-dimethylpropyl, n-hexyl, 2-methylpentyl, 3-methylpentyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl and 3,3-dimethylpropyl; -W- is wherein the dashed lines indicate attachment to the rest of the molecule; -Nu is -N(R 7 R 7a); -Ar- is selected from the group consisting of wherein dashed lines indicate attachment to the rest of the prodrug, -Z 1 - is selected from the group consisting of -O-, -S- and -N(R 7)-, and -Z 2 - is -N(R 7)-; and -Z 1 - is selected from the group consisting of -O-, -S- and -N(R 7)-, and -Z 2 - is -N(R 7)-; and -R 7, -R 7a are independently of each other selected from the group consisting of -H, C 1-6 alkyl, C 2-6 alkenyl and C 2-6 alkynyl.