The present invention relates to modified forms of C-peptide, and methods for their use. In one aspect, the modified forms of C-peptide comprise PEGylated C-peptide derivatives comprising at least one PEG group attached to the N-terminus, which exhibit superior pharmacokinetic and biological activity in vivo.本発明は修飾型Cペプチドとその利用方法に関する。1つの態様において、修飾型Cペプチドは、N末端に結合した少なくとも1つのPEG基を含み、インビボで優れた薬物動態と生物学的活性を示すPEG化Cペプチド誘導体を含む。