Site-specific modification of anti-angiogenesis peptide HM-3 by polyethylene glycol molecular weight of 20 kDa

HM-3, an RGD modified endostatin-derived polypeptide, is a potent angiogenesis inhibitor synthesized in our laboratory. Its robust inhibitory effects on endothelial cell migration and tumour growth have been demonstrated by in vivo and in vitro activity assays. However, the drug has relatively short half-life in vivo. For the purpose of prolonging HM-3 half-life and retaining the safety and efficacy of the peptide, the study chose methoxy-polyethylene glycol-Succinimidyl Carbonate (SC-mPEG, molecular weight 20 kDa, named SC-mPEG₂₀k) to specifically modify its N terminus. Compared with HM-3, the site-specific mono-PEGylated peptide PEG₂₀k-HM-3 was shown the same activity in the inhibition of B16F10 tumour in vivo (the inhibitory effect of PEG₂₀k-HM-3, HM-3 and Taxol were 44.35, 39.68%, respectively), while the frequency of drug-administering reduced from twice a day to once every 3 days. Its rate of in vitro degradation in serum was markedly reduced (72.78% could still be detected after 132 h). Histochemistry and immunohistochemistry analysis showed that both HM-3 and PEG₂₀k-HM-3 induced large areas of continuous necrosis within tumours and significantly reduced the vessel density compared to control. It might be a breakthrough in PEG modification field to modify a small peptide with a large PEG and reach a good result.