Pauletti G M, Gangwar S, Wang B, Borchardt R T
Department of Pharmaceutical Chemistry, The University of Kansas, Lawrence 66047, USA.
Pharm Res. 1997 Jan;14(1):11-7. doi: 10.1023/a:1012091014242.
To evaluate a cyclic phenylpropionic acid prodrug of a model hexapeptide (H-Trp-Ala-Gly-Gly-Asp-Ala-OH) as a novel approach to enhance the membrane permeation of a peptide and stabilize it to metabolism.
Conversion to the linear hexapeptide was studied at 37 degrees C in HBSS, pH 7.4, and in various biological milieus having measurable esterase activities. Transport and metabolism characteristics were assessed using the Caco-2 cell culture model.
In aqueous buffered solution, pH 7.4, the cyclic prodrug degraded quantitatively (t1/2 = 1795 +/- 289 min) to the linear hexapeptide and the lactone. Substantially faster degradation of the cyclic prodrug was observed in 90% human plasma (t1/2 = 508 +/- 24 min), and in homogenates of Caco-2 cells (t1/2 = 940 +/- 13 min), the rat intestinal mucosa (t1/2 = 1286 +/- 32 min), and rat liver (t1/2 = 840 +/- 42 min). Pretreatment of these biological media with paraoxon significantly decreased the degradation rate of the prodrug. When applied to the apical side of Caco-2 cell monolayers, the cyclic prodrug was significantly more stable than the hexapeptide and at least 71-fold more able to permeate (P(app) = 1.21 +/- 0.12 X 10(-7) cm/s) than was the parent peptide (P(app) < or = 0.17 x 10(-8) cm/s). In the presence of 0.1 mM palmitoyl-DL-carnitine, the transport rate of the cyclic prodrug (P(app) = 2.19 X 10(-6) cm/s) was 1250-fold greater than that of the linear hexapeptide.
Preparation of a cyclic peptide using a phenylpropionic acid promoiety reduced the lability of the peptide to peptidase metabolism and substantially increased its permeation through biological membranes. In various biological media the parent peptide was released from the prodrug by an apparent esterase-catalyzed reaction, sensitive to paraoxon inhibition.
评估一种模型六肽（H-Trp-Ala-Gly-Gly-Asp-Ala-OH）的环状苯丙酸前药，作为增强肽的膜通透性并使其对代谢稳定的一种新方法。
在37℃、pH 7.4的HBSS以及具有可测量酯酶活性的各种生物环境中研究其向线性六肽的转化。使用Caco-2细胞培养模型评估转运和代谢特性。
在pH 7.4的水性缓冲溶液中，环状前药定量降解（t1/2 = 1795 ± 289分钟）为线性六肽和内酯。在90%人血浆（t1/2 = 508 ± 24分钟）、Caco-2细胞匀浆（t1/2 = 940 ± 13分钟）、大鼠肠黏膜（t1/2 = 1286 ± 32分钟）和大鼠肝脏（t1/2 = 840 ± 42分钟）中观察到环状前药降解明显更快。用对氧磷预处理这些生物介质可显著降低前药的降解速率。当应用于Caco-2细胞单层的顶端时，环状前药比六肽明显更稳定，并且其透过能力（P(app) = 1.21 ± 0.12 × 10(-7) cm/s）比母体肽（P(app) ≤0.17 × 10(-8) cm/s）至少高71倍。在存在0.1 mM棕榈酰-DL-肉碱的情况下，环状前药的转运速率（P(app) = 2.19 × 10(-6) cm/s）比线性六肽高1250倍。
使用苯丙酸部分制备环状肽降低了肽对肽酶代谢的不稳定性，并显著增加了其通过生物膜的通透性。在各种生物介质中，母体肽通过明显的酯酶催化反应从前药中释放出来，该反应对氧磷抑制敏感。
