4′-Ethynyl Nucleoside Analogs: Potent Inhibitors of Multidrug-Resistant Human Immunodeficiency Virus Variants In Vitro

Abstract

A series of 4′-ethynyl (4′-E) nucleoside analogs were designed, synthesized, and identified as being active against a wide spectrum of human immunodeficiency viruses (HIV), including a variety of laboratory strains of HIV-1, HIV-2, and primary clinical HIV-1 isolates. Among such analogs examined, 4′-E-2′-deoxycytidine (4′-E-dC), 4′-E-2′-deoxyadenosine (4′-E-dA), 4′-E-2′-deoxyribofuranosyl-2,6-diaminopurine, and 4′-E-2′-deoxyguanosine were the most potent and blocked HIV-1 replication with 50% effective concentrations ranging from 0.0003 to 0.01 μM in vitro with favorable cellular toxicity profiles (selectivity indices ranging 458 to 2,600). These 4′-E analogs also suppressed replication of various drug-resistant HIV-1 clones, including HIV-1M41L/T215Y, HIV-1K65R, HIV-1L74V, HIV-1M41L/T69S-S-G/T215Y, and HIV-1A62V/V75I/F77L/F116Y/Q151M. Moreover, these analogs inhibited the replication of multidrug-resistant clinical HIV-1 strains carrying a variety of drug resistance-related amino acid substitutions isolated from HIV-1-infected individuals for whom 10 or 11 different anti-HIV-1 agents had failed. The 4′-E analogs also blocked the replication of a non-nucleoside reverse transcriptase inhibitor-resistant clone, HIV-1Y181C, and showed an HIV-1 inhibition profile similar to that of zidovudine in time-of-drug-addition assays. The antiviral activity of 4′-E-thymidine and 4′-E-dC was blocked by the addition of thymidine and 2′-deoxycytidine, respectively, while that of 4′-E-dA was not affected by 2′-deoxyadenosine, similar to the antiviral activity reversion feature of 2′,3′-dideoxynucleosides, strongly suggesting that 4′-Eanalogs belong to the family of nucleoside reverse transcriptase inhibitors. Further development of 4′-E analogs as potential therapeutics for infection with multidrug-resistant HIV-1 is warranted.

Mechanism of Inhibition of HIV-1 Reverse Transcriptase by 4′-Ethynyl-2-fluoro-2′-deoxyadenosine Triphosphate, a Translocation-defective Reverse Transcriptase Inhibitor

“…This property results in termination of further viral DNA synthesis upon incorporation of the inhibitor into the nascent viral DNA. We have shown (10,13) that certain nucleoside analogs that retain the 3Ј-OH group can exert potent antiviral activity. One of these, EFdA, inhibits HIV-1 replication in PBMCs with a potency that is several orders of magnitude greater than that of any of the current FIGURE 5.…”

A New Paradigm for Developing Antiviral Drugs Exemplified by the Development of Supremely High Anti-HIV Active EFdA

“…Additionally, the three were also active against a non-nucleoside reverse transcriptase inhibitorresistant Y181C. Further, the three purine derivatives were highly potent against the HIVs isolated from seven heavily drug-experienced patients with acquired immune deficiency syndrome (AIDS) as efficiently as against wild-type HIV [14,15,26]. Thus, 4'EdA, 4'Ed2AA, and 4'EdG were highly potent against all the existing HIVs.…”

“…Next, to study the SAR of 4'SdNs and develop 4'SdNs having more potent anti-HIV activity and less toxicity than 4'MdNs, 4'SdNs having various kinds of 4'-C-substituents and nucleobases were synthesized and evaluated for their biological activity [8][9][10][11][12][13][14][15]. While we were working on our project, the anti-HIV activity of several 4'SdNs was reported by the Syntex group [16][17][18][19][20][21][22] and others [23,24].…”

A Novel Colorimetric Assay for CXCR4 and CCR5 Tropic Human Immunodeficiency Viruses

“…A CXCR4 antagonist, T-140 (Fujii & Tamamura, 2001), and the following protease inhibitors (PIs): VX-478 and nelfinavir (Livington et al, 1995;Witvrouw et al, 2004), were kindly provided by N Fujii (Kyoto University, Kyoto, Japan). A CCR5 antagonist, TAK-779 (Baba et al, 1999) Kanbe et al, 1999;Soda et al, 1999) Ltd,Osaka,Japan) and 0.5 µg/ml of phytohaemagglutinin (PHA; Sigma) as previously described (Kodama et al, 2001 …”

“…The MTT assay using MT-4 cells was performed as previously described (Kodama et al, 2001 (Kodama et al, 1996).…”