Hugele Agathe, Löffler Susanne, Molina Belén Hernández, Guillon Melina, Montaser Ahmed B, Auriola Seppo, Huttunen Kristiina M
School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Kuopio, Finland.
Front Pharmacol. 2022 Oct 20;13:1034964. doi: 10.3389/fphar.2022.1034964. eCollection 2022.
A prodrug approach is a powerful method to temporarily change the physicochemical and thus, pharmacokinetic properties of drugs. However, in site-selective targeted prodrug delivery, tissue or cell-specific bioconverting enzyme is needed to be utilized to release the active parent drug at a particular location. Unfortunately, ubiquitously expressed enzymes, such as phosphatases and carboxylesterases are well used in phosphate and ester prodrug applications, but less is known about enzymes selectively expressed, e.g., in the brain and enzymes that can hydrolyze more stable prodrug bonds, such as amides and carbamates. In the present study, L-type amino acid transporter 1 (LAT1)-utilizing amide prodrugs bioconverting enzyme was identified by gradually exploring the environment and possible determinants, such as pH and metal ions, that affect amide prodrug hydrolysis. Based on inducement by cobalt ions and slightly elevated pH (8.5) as well as localization in plasma, liver, and particularly in the brain, aminopeptidase B was proposed to be responsible for the bioconversion of the majority of the studied amino acid amide prodrugs. However, this enzyme hydrolyzed only those prodrugs that contained an aromatic promoiety (L-Phe), while leaving the aliphatic promoeities (L-Lys) and the smallest prodrug (with L-Phe promoiety) intact. Moreover, the parent drugs' structure (flexibility and the number of aromatic rings) largely affected the bioconversion rate. It was also noticed in this study, that there were species differences in the bioconversion rate by aminopeptidase B (rodents > human), although the - correlation of the studied prodrugs was relatively accurate.
前药方法是一种改变药物物理化学性质进而改变其药代动力学性质的有效方法。然而，在 site - selective 靶向前药递送中，需要利用组织或细胞特异性生物转化酶在特定位置释放活性母体药物。不幸的是，普遍表达的酶，如磷酸酶和羧酸酯酶，在磷酸盐和酯前药应用中得到了很好的应用，但对于选择性表达的酶，如在大脑中表达的酶以及能够水解更稳定前药键（如酰胺和氨基甲酸酯）的酶，人们了解较少。在本研究中，通过逐步探索影响酰胺前药水解的环境和可能的决定因素，如pH值和金属离子，鉴定了利用L型氨基酸转运体1（LAT1）的酰胺前药生物转化酶。基于钴离子的诱导、略高的pH值（8.5）以及在血浆、肝脏尤其是大脑中的定位，氨基肽酶B被认为是大多数研究的氨基酸酰胺前药生物转化的原因。然而，这种酶只水解那些含有芳香族部分（L - Phe）的前药，而脂肪族部分（L - Lys）和最小的前药（带有L - Phe部分）则保持完整。此外，母体药物的结构（柔韧性和芳香环的数量）在很大程度上影响生物转化率。在本研究中还注意到，氨基肽酶B的生物转化率存在物种差异（啮齿动物>人类），尽管所研究前药的相关性相对准确。
