Novartis Institutes for Biomedical Research, Inc., Cambridge, MA 02139, USA.
Antimicrob Agents Chemother. 2010 May;54(5):1981-7. doi: 10.1128/AAC.01236-09. Epub 2010 Feb 22.
The current standard of care for hepatitis C virus (HCV) infection, pegylated alpha interferon in combination with ribavirin, has a limited response rate and adverse side effects. Drugs targeting viral proteins are in clinical development, but they suffer from the development of high viral resistance. The inhibition of cellular proteins that are essential for viral amplification is thought to have a higher barrier to the emergence of resistance. Three cyclophilin inhibitors, the cyclosporine analogs DEBIO-025, SCY635, and NIM811, have shown promising results for the treatment of HCV infection in early clinical trials. In this study, we investigated the frequency and mechanism of resistance to cyclosporine (CsA), NIM811, and a structurally unrelated cyclophilin inhibitor, SFA-1, in replicon-containing Huh7 cells. Cross-resistance between all clones was observed. NIM811-resistant clones were selected only after obtaining initial resistance to either CsA or SFA-1. The time required to select resistance against cyclophilin inhibitors was significantly longer than that required for resistance selection against viral protein inhibitors, and the achievable resistance level was substantially lower. Resistance to cyclophilin inhibitors was mediated by amino acid substitutions in NS3, NS5A, and NS5B, with NS5A mutations conferring the majority of resistance. Mutation D320E in NS5A mediated most of the resistance conferred by NS5A. Taken together, the results indicate that there is a very low frequency and level of resistance to cyclophilin-binding drugs mediated by amino acid substitutions in three viral proteins. The interaction of cyclophilin with NS5A seems to be the most critical, since the NS5A mutations have the largest impact on resistance.
目前丙型肝炎病毒（HCV）感染的标准治疗方法是聚乙二醇干扰素α与利巴韦林联合治疗，但该方法应答率有限，且具有不良反应。针对病毒蛋白的药物正在临床开发中，但它们存在病毒耐药性发展的问题。抑制对病毒扩增至关重要的细胞蛋白被认为具有更高的耐药性出现障碍。三种亲环素抑制剂，即环孢素类似物 DEBIO-025、SCY635 和 NIM811，在早期临床试验中显示出治疗 HCV 感染的良好效果。在这项研究中，我们研究了亲环素（CsA）、NIM811 和一种结构上不相关的亲环素抑制剂 SFA-1 在含有复制子的 Huh7 细胞中耐药的频率和机制。所有克隆之间都观察到交叉耐药性。只有在获得对 CsA 或 SFA-1 的初始耐药性后，才选择 NIM811 耐药克隆。获得对亲环素抑制剂的耐药性所需的时间明显长于获得对病毒蛋白抑制剂的耐药性所需的时间，而且可达到的耐药水平要低得多。亲环素抑制剂的耐药性是由 NS3、NS5A 和 NS5B 中的氨基酸取代介导的，其中 NS5A 突变赋予了大部分耐药性。NS5A 中的 D320E 突变介导了 NS5A 赋予的大部分耐药性。总之，结果表明，三种病毒蛋白中的氨基酸取代介导的对亲环素结合药物的耐药性频率和水平非常低。亲环素与 NS5A 的相互作用似乎是最关键的，因为 NS5A 突变对耐药性的影响最大。
