Department of Antiviral Drug Discovery, Achillion Pharmaceuticals, New Haven, Connecticut, USA.
Antimicrob Agents Chemother. 2013 Jul;57(7):3168-77. doi: 10.1128/AAC.02630-12. Epub 2013 Apr 29.
Treatment of hepatitis C patients with direct-acting antiviral drugs involves the combination of multiple small-molecule inhibitors of distinctive mechanisms of action. ACH-806 (or GS-9132) is a novel, small-molecule inhibitor specific for hepatitis C virus (HCV). It inhibits viral RNA replication in HCV replicon cells and was active in genotype 1 HCV-infected patients in a proof-of-concept clinical trial (1). Here, we describe a potential mechanism of action (MoA) wherein ACH-806 alters viral replication complex (RC) composition and function. We found that ACH-806 did not affect HCV polyprotein translation and processing, the early events of the formation of HCV RC. Instead, ACH-806 triggered the formation of a homodimeric form of NS4A with a size of 14 kDa (p14) both in replicon cells and in Huh-7 cells where NS4A was expressed alone. p14 production was negatively regulated by NS3, and its appearance in turn was associated with reductions in NS3 and, especially, NS4A content in RCs due to their accelerated degradation. A previously described resistance substitution near the N terminus of NS3, where NS3 interacts with NS4A, attenuated the reduction of NS3 and NS4A conferred by ACH-806 treatment. Taken together, we show that the compositional changes in viral RCs are associated with the antiviral activity of ACH-806. Small molecules, including ACH-806, with this novel MoA hold promise for further development and provide unique tools for clarifying the functions of NS4A in HCV replication.
治疗丙型肝炎患者的直接作用抗病毒药物涉及多种作用机制独特的小分子抑制剂的联合应用。ACH-806（或 GS-9132）是一种新型的、针对丙型肝炎病毒（HCV）的小分子抑制剂。它在 HCV 复制子细胞中抑制病毒 RNA 复制，并在概念验证临床试验中对感染基因型 1 HCV 的患者具有活性（1）。在这里，我们描述了一种潜在的作用机制（MoA），其中 ACH-806 改变病毒复制复合物（RC）的组成和功能。我们发现 ACH-806 不影响 HCV 多蛋白的翻译和加工，即 HCV RC 形成的早期事件。相反，ACH-806 触发 NS4A 形成一种大小为 14 kDa（p14）的同源二聚体形式，无论是在复制子细胞中还是在单独表达 NS4A 的 Huh-7 细胞中。p14 的产生受到 NS3 的负调控，其出现反过来又与 RC 中 NS3 和特别是 NS4A 含量的减少相关，因为它们的降解加速了。先前在 NS3 的 N 端附近描述的抗性取代，其中 NS3 与 NS4A 相互作用，削弱了 ACH-806 治疗所赋予的 NS3 和 NS4A 的减少。总之，我们表明病毒 RC 中的组成变化与 ACH-806 的抗病毒活性相关。具有这种新型 MoA 的小分子，包括 ACH-806，具有进一步开发的潜力，并为阐明 NS4A 在 HCV 复制中的功能提供了独特的工具。
