Esposito P, Barbero L, Caccia P, Caliceti P, D'Antonio M, Piquet G, Veronese F M
Industria Farmaceutica Serono, Drug Delivery Systems, Via Ribes 5, BioIndustry Park del Canavese, 10010 Colleretto Giacosa (TO), Italy.
Adv Drug Deliv Rev. 2003 Sep 26;55(10):1279-91. doi: 10.1016/s0169-409x(03)00109-1.
Synthetically produced GRF1-29 (Sermorelin) has an amino acid composition identical to the N-terminal 29 amino acids sequence of the natural hypothalamic GHRH1-44 (Figure 1). It maintains bioactivity in vitro and is almost equally effective in eliciting secretion of endogenous growth hormone in vivo. The main drawbacks associated with the pharmaceutical use of hGRF1-29 relate to its short half-life in plasma, about 10-20 min in humans, which is caused mostly by renal ultrafiltration and enzymatic degradation at the N terminus. PEGylation has been considered as one valid approach to obtain more stable forms of the peptide, with a longer in vivo half-life and ultimately with increased pharmacodynamic response along the somatotropic axis (endogenous GH, IGF-1 levels). Different PEGylated GRF conjugates were obtained and their bioactivity was tested in vitro and in vivo by monitoring endogenous growth hormone (GH) serum levels after intravenous (i.v.) injection in rats, and intravenous and subcutaneous (s.c.) injection in pigs. It was found that GRF-PEG conjugates are able to bind and activate the human GRF receptor, although with different potency. The effect of PEG molecular weight, number of PEG chains bound and position of PEGylation site on GRF activity were investigated. Mono-PEGylated isomers with a PEG5000 polymer chain linked to Lys 12 or Lys 21 residues, showed high biological activity in vitro, which is similar to that of hGRF1-29, and a higher pharmacodynamic response as compared to unmodified GRF molecule.
人工合成的GRF1-29（生长激素释放因子）的氨基酸组成与天然下丘脑生长激素释放激素1-44的N端29个氨基酸序列相同（图1）。它在体外保持生物活性，并且在体内诱导内源性生长激素分泌方面几乎同样有效。与hGRF1-29药物使用相关的主要缺点与其在血浆中的半衰期短有关，在人类中约为10-20分钟，这主要是由肾脏超滤和N端的酶促降解引起的。聚乙二醇化已被认为是获得更稳定形式肽的一种有效方法，具有更长的体内半衰期，并最终沿生长激素轴（内源性生长激素、胰岛素样生长因子-1水平）增强药效学反应。获得了不同的聚乙二醇化GRF缀合物，并通过监测大鼠静脉注射（i.v.）、猪静脉注射和皮下注射（s.c.）后内源性生长激素（GH）血清水平，在体外和体内测试了它们的生物活性。发现GRF-PEG缀合物能够结合并激活人GRF受体，尽管效力不同。研究了聚乙二醇分子量、结合的聚乙二醇链数量和聚乙二醇化位点位置对GRF活性的影响。与Lys 12或Lys 21残基连接有PEG5000聚合物链的单聚乙二醇化异构体在体外表现出高生物活性，类似于hGRF1-29，并且与未修饰的GRF分子相比具有更高的药效学反应。
