Youn Yu Seok, Kwon Min Jung, Na Dong Hee, Chae Su Young, Lee Seulki, Lee Kang Choon
College of Pharmacy, Pusan National University, Jangjun-dong, Geumjeong-gu, Busan 609-735, Korea.
J Control Release. 2008 Jan 4;125(1):68-75. doi: 10.1016/j.jconrel.2007.10.008. Epub 2007 Oct 22.
The purpose of this study was to demonstrate the biological potentials of PEGylated salmon calcitonin (PEG-sCT) derivatives administered intratracheally and their dependences on PEG Mw (1, 2, 5 kDa). Initially, three different PEG-sCT derivatives were site-specifically synthesized by attaching PEG to the Lys(18)-amine. In an attempt to examine the pulmonary feasibilities of these derivatives, the following evaluations were undertaken to determine their; (i) proteolytic resistances to pulmonary enzymes, (ii) bioactivities, and (iii) pulmonary pharmacokinetic and pharmacologic profiles. The results obtained showed that the pulmonary stabilities and pharmacokinetic properties of these derivatives were greatly improved by increasing PEG Mw. PEG-sCTs had 10.5-, 40.1-, and 1066.0-fold greater stabilities than that of sCT in rat lung homogenates. Moreover, all pharmacokinetic parameters (AUC(inf), C(max), t(1/2), and others) of these derivatives in endotracheally cannulated rats were significantly improved by PEGylation. Specifically, C(max) values increased on increasing PEG Mw, i.e., 78.1+/-21.1, 102.9+/-9.1, and 115.2+/-5.7 for 1, 2, 5 kDa, respectively, vs. 54.8+/-3.9 ng/mL for sCT. Their circulating t(1/2) values also increased to 53.9+/-6.0, 100.7+/-21.7, and 119.4+/-13.7 min, respectively, vs. 34.6+/-7.6 min for sCT. Despite having the best properties, Lys(18)-PEG(5k)-sCT was found to have significantly lower hypocalcemic efficacy than other PEG-sCTs, probably due to its reduced intrinsic bioactivity ( approximately 30% vs. sCT). Rather, Lys(18)-PEG(2k)-sCT showed the most promising pulmonary potential because of its well-preserved bioactivity (>80% of sCT). Taken together, our findings suggest that the site-specific substitution to peptides like sCT with a PEG of an appropriate size offers optimized therapeutic potential by dual advantages, i.e., (i) increased proteolytic stability and (ii) extended circulating half-life in terms of intrapulmonary delivery.
本研究的目的是证明经气管内给药的聚乙二醇化鲑鱼降钙素（PEG-sCT）衍生物的生物学潜力及其对聚乙二醇分子量（1、2、5 kDa）的依赖性。最初，通过将聚乙二醇连接到赖氨酸（18）-胺上，位点特异性合成了三种不同的PEG-sCT衍生物。为了研究这些衍生物在肺部的可行性，进行了以下评估以确定它们的：（i）对肺部酶的蛋白水解抗性，（ii）生物活性，以及（iii）肺部药代动力学和药理学特征。所得结果表明，通过增加聚乙二醇分子量，这些衍生物的肺部稳定性和药代动力学性质得到了极大改善。在大鼠肺匀浆中，PEG-sCT的稳定性分别比sCT高10.5倍、40.1倍和1066.0倍。此外，聚乙二醇化显著改善了这些衍生物在气管插管大鼠中的所有药代动力学参数（AUC(inf)、C(max)、t(1/2)等）。具体而言，C(max)值随着聚乙二醇分子量的增加而增加，即1 kDa、2 kDa和5 kDa的C(max)值分别为78.1±21.1、102.9±9.1和115.2±5.7，而sCT的C(max)值为54.8±3.9 ng/mL。它们的循环t(1/2)值也分别增加到53.9±6.0、100.7±21.7和119.4±13.7分钟，而sCT的t(1/2)值为34.6±7.6分钟。尽管Lys(18)-PEG(5k)-sCT具有最佳性能，但发现其降钙作用效力明显低于其他PEG-sCT，这可能是由于其内在生物活性降低（约为sCT的30%）。相反，Lys(18)-PEG(2k)-sCT因其良好保留的生物活性（>sCT的80%）而显示出最有前景的肺部应用潜力。综上所述，我们的研究结果表明，用适当大小的聚乙二醇对sCT等肽进行位点特异性取代可通过双重优势提供优化的治疗潜力，即（i）提高蛋白水解稳定性和（ii）就肺内给药而言延长循环半衰期。
