Wainberg M A, Miller M D, Quan Y, Salomon H, Mulato A S, Lamy P D, Margot N A, Anton K E, Cherrington J M
McGill University AIDS Center, Jewish General Hospital, Montreal, Quebec, Canada.
Antivir Ther. 1999;4(2):87-94. doi: 10.1177/135965359900400205.
9-(2-phosphonomethoxypropyl)adenine (PMPA) has demonstrated remarkable anti-simian immunodeficiency virus (SIV) activity in macaque models of SIV infection and transmission prevention. Recently, PMPA and its oral prodrug, bis-POC PMPA, have also shown potent anti-human immunodeficiency virus type 1 (HIV-1) activity in Phase I clinical studies. In vitro experiments were performed to address the resistance properties of PMPA. After eight passages in increasing concentrations of PMPA, HIV-1IIIB was able to grow in the presence of 2 microM PMPA, fivefold above the IC50 of PMPA for wild-type parental virus. Sequence analysis of the reverse transcriptase (RT) genes from four of 15 RT clones demonstrated the presence of a K65R substitution in RT and recombinant HIV expressing the K65R RT mutation showed a threefold to fourfold increase in IC50 value for PMPA as compared to wild-type. Additional experiments demonstrated that viruses expressing other nucleoside-associated RT resistance mutations all showed wild-type or < threefold reduced susceptibility to PMPA in vitro. Interestingly, lamivudine-resistant viruses expressing the M184V RT mutation showed wild-type to slightly increased susceptibility to PMPA in vitro and addition of the M184V mutation to HIV with the K65R mutation resulted in reversion to wild-type susceptibility for PMPA. In agreement with the cell culture findings, Escherichia coli-expressed K65R RT showed fivefold reduced susceptibility to PMPA diphosphate, the active moiety of PMPA. Furthermore, in combination experiments, PMPA with hydroxyurea showed synergistic inhibition of HIV replication in vitro. The potent antiretroviral activity and favourable resistance profile of PMPA and bis-POC PMPA are being further investigated in ongoing clinical trials.
9-(2-膦酰甲氧基丙基)腺嘌呤（PMPA）在猕猴的猿猴免疫缺陷病毒（SIV）感染和传播预防模型中已显示出显著的抗SIV活性。最近，PMPA及其口服前药双-POC PMPA在I期临床研究中也表现出强大的抗人类免疫缺陷病毒1型（HIV-1）活性。进行了体外实验以研究PMPA的耐药特性。在浓度不断增加的PMPA中传代八次后，HIV-1IIIB能够在2 microM PMPA存在的情况下生长，这一浓度比野生型亲本病毒的PMPA IC50高五倍。对15个逆转录酶（RT）克隆中的4个进行RT基因序列分析，结果显示RT中存在K65R替代，表达K65R RT突变的重组HIV对PMPA的IC50值比野生型增加了三到四倍。额外的实验表明，表达其他核苷相关RT耐药突变的病毒在体外对PMPA的敏感性均显示为野生型或降低不到三倍。有趣的是，表达M184V RT突变的拉米夫定耐药病毒在体外对PMPA的敏感性显示为野生型或略有增加，并且将M184V突变添加到具有K65R突变的HIV中会导致对PMPA的敏感性恢复到野生型。与细胞培养结果一致，大肠杆菌表达的K65R RT对PMPA二磷酸（PMPA的活性部分）的敏感性降低了五倍。此外，在联合实验中，PMPA与羟基脲在体外对HIV复制显示出协同抑制作用。PMPA和双-POC PMPA强大的抗逆转录病毒活性和良好的耐药特性正在正在进行的临床试验中进一步研究。
