CCR5 Antagonist TD-0680 Uses a Novel Mechanism for Enhanced Potency against HIV-1 Entry, Cell-mediated Infection, and a Resistant Variant

• Published in: The Journal of biological chemistry Vol. 287; no. 20; pp. 16499 - 16509
• Main Authors: Kang, Yuanxi, Wu, Zhiwei, Lau, Terrence C.K., Lu, Xiaofan, Liu, Li, Cheung, Allen K.L., Tan, Zhiwu, Ng, Jenny, Liang, Jianguo, Wang, Haibo, Li, Saikam, Zheng, Bojian, Li, Ben, Chen, Li, Chen, Zhiwei
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 11.05.2012; American Society for Biochemistry and Molecular Biology
• Subjects: Amides - pharmacology; Anti-HIV Agents - pharmacology; Antiviral Agents; Binding Mechanism; Binding Sites; CCR5 Antagonist; CCR5 Receptor Antagonists; Cell Line; Cyclohexanes - pharmacology; Drug Discovery; Entry Inhibitor; HIV Infections - drug therapy; HIV Infections - metabolism; HIV Infections - transmission; HIV-1; HIV-1 - physiology; Humans; Maraviroc; Microbiology; Molecular Docking; Protein Structure, Secondary; Quaternary Ammonium Compounds - pharmacology; Receptors, CCR5 - metabolism; Small Molecules; Sulfonamides - pharmacology; TD-0680; Triazoles - pharmacology; Tropanes - pharmacology; Virus Entry; Virus Internalization - drug effects; Virus Replication - drug effects; Virus Replication - physiology; HIV-1; Virus Entry; Molecular Docking; CCR5 Antagonist; Antiviral Agents; Small Molecules; Binding Mechanism; Drug Discovery; Entry Inhibitor; TD-0680
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.354084

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 EC50 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. Maraviroc-resistant HIV-1 posts challenges to CCR5 antagonist discovery. CCR5 antagonist TD-0680 employs a novel mechanism for subnanomolar potency against HIV-1 entry, cell-mediated infection, and a TAK-779/Maraviroc-resistant variant. Distinct binding mode of TD-0680 accounts for its enhanced potency. Our findings have implications for drug design and developing TD-0680 as an antiretroviral and/or as a microbicide against HIV-1.