AIDS Institute, Department of Microbiology and Research Center for Infection and Immunity, Li Ka Shing Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China.
J Biol Chem. 2012 May 11;287(20):16499-509. doi: 10.1074/jbc.M112.354084. Epub 2012 Mar 23.
Regardless of the route of transmission, R5-tropic HIV-1 predominates early in infection, rendering C-C chemokine receptor type 5 (CCR5) antagonists as attractive agents not only for antiretroviral therapy but also for prevention. Here, we report the specificity, potency, and underlying mechanism of action of a novel small molecule CCR5 antagonist, TD-0680. TD-0680 displayed the greatest potency against a diverse group of R5-tropic HIV-1 and SIV strains when compared with its prodrug, TD-0232, the Food and Drug Administration-approved CCR5 antagonist Maraviroc, and TAK-779, with EC(50) values in the subnanomolar range (0.09-2.29 nm). Importantly, TD-0680 was equally potent at blocking envelope-mediated cell-cell fusion and cell-mediated viral transmission as well as the replication of a TAK-779/Maraviroc-resistant HIV-1 variant. Interestingly, TD-0232 and TD-0680 functioned differently despite binding to a similar transmembrane pocket of CCR5. Site-directed mutagenesis, drug combination, and antibody blocking assays identified a novel mechanism of action of TD-0680. In addition to binding to the transmembrane pocket, the unique exo configuration of this molecule protrudes and sterically blocks access to the extracellular loop 2 (ECL2) region of CCR5, thereby interrupting the interaction between virus and its co-receptor more effectively. This mechanism of action was supported by the observations of similar TD-0680 potency against CD4-dependent and -independent SIV strains and by molecular docking analysis using a CCR5 model. TD-0680, therefore, merits development as an anti-HIV-1 agent for therapeutic purposes and/or as a topical microbicide for the prevention of sexual transmission of R5-tropic HIV-1.
无论传播途径如何，R5 嗜性 HIV-1 在感染早期占主导地位，这使得 C-C 趋化因子受体 5（CCR5）拮抗剂不仅成为抗逆转录病毒治疗的有吸引力的药物，而且也成为预防的有吸引力的药物。在这里，我们报告了一种新型小分子 CCR5 拮抗剂 TD-0680 的特异性、效力和作用机制。与前药 TD-0232、已获美国食品和药物管理局批准的 CCR5 拮抗剂马拉维若（Maraviroc）和 TAK-779 相比，TD-0680 对多种 R5 嗜性 HIV-1 和 SIV 株具有最大的效力，EC50 值在亚纳摩尔范围内（0.09-2.29nm）。重要的是，TD-0680 同样能够有效阻断包膜介导的细胞-细胞融合和细胞介导的病毒传播，以及 TAK-779/马拉维若耐药 HIV-1 变异体的复制。有趣的是，尽管 TD-0232 和 TD-0680 结合到 CCR5 的相似跨膜口袋，但它们的功能不同。定点突变、药物组合和抗体阻断试验确定了 TD-0680 的一种新作用机制。除了结合到跨膜口袋外，该分子独特的外向构象突出并在空间上阻止了对 CCR5 的细胞外环 2（ECL2）区域的进入，从而更有效地阻断了病毒与其共受体之间的相互作用。这一作用机制得到了以下观察结果的支持：TD-0680 对 CD4 依赖性和非依赖性 SIV 株具有相似的效力，以及使用 CCR5 模型进行的分子对接分析。因此，TD-0680 值得开发为治疗目的的抗 HIV-1 药物和/或作为预防 R5 嗜性 HIV-1 性传播的局部杀微生物剂。
