The present invention relates to a CNP prodrug or a pharmaceutically acceptable salt thereof comprising a CNP moiety -D; and a carrier moiety —Z that is conjugated through a moiety -L2- to a reversible prodrug linker moiety -L1-, which reversible prodrug linker moiety -L1- is covalently and reversibly conjugated to -D; wherein -L2- is a chemical bond or a spacer; and —Z is a polymer having a molecular weight of at least 10 kDa. It further relates to pharmaceutical compositions comprising the CNP prodrug or a pharmaceutically acceptable salt thereof, their use as a medicament and to methods of treatment.