Andreatta Kristen N, Goodman Derrick D, Miller Michael D, White Kirsten L
Gilead Sciences, Inc., Foster City, California, USA
Gilead Sciences, Inc., Foster City, California, USA.
Antimicrob Agents Chemother. 2015;59(6):3441-9. doi: 10.1128/AAC.00040-15. Epub 2015 Mar 30.
The most common pattern of emergent resistance in the phase III clinical trials of coformulated elvitegravir (EVG)-cobicistat (COBI)-emtricitabine (FTC)-tenofovir disoproxil fumarate (TDF) was the EVG resistance substitution E92Q in integrase (IN) with the FTC resistance substitution M184V in reverse transcriptase (RT), with or without the tenofovir (TFV) resistance substitution K65R. In this study, the effect of these IN and RT substitutions alone and in combination in the same genome on susceptibility to antiretroviral inhibitors and viral replication fitness was characterized. Single resistance substitutions (E92Q in IN [IN-E92Q], M184V in RT [RT-M184V], and K65R in RT [RT-K65R]) specifically affected susceptibility to the corresponding inhibitor classes, with no cross-class resistance observed. The IN-E92Q mutant displayed reduced susceptibility to EVG (50-fold), which was not impacted by the addition of RT-M184V or RT-K65R/M184V. Viruses containing RT-M184V had high-level resistance to FTC (>1,000-fold) that was not affected by the addition of IN-E92Q or RT-K65R. During pairwise growth competitions, each substitution contributed to decreased viral fitness, with the RT-K65R/M184V + IN-E92Q triple mutant being the least fit in the absence of drug. In the presence of drug concentrations approaching physiologic levels, however, drug resistance offset the replication defects, resulting in single mutants outcompeting the wild type with one drug present, and double and triple mutants outcompeting single mutants with two drugs present. Taken together, these results suggest that the reduced replication fitness and phenotypic resistance associated with RT and IN resistance substitutions are independent and additive. In the presence of multiple drugs, viral growth is favored for viruses with multiple substitutions, despite the presence of fitness defects.
在复方elvitegravir（EVG）-考比司他（COBI）-恩曲他滨（FTC）-替诺福韦酯（TDF）的III期临床试验中，最常见的紧急耐药模式是整合酶（IN）中出现EVG耐药替代E92Q，同时逆转录酶（RT）中出现FTC耐药替代M184V，有或没有替诺福韦（TFV）耐药替代K65R。在本研究中，对这些IN和RT替代单独以及在同一基因组中组合对抗逆转录病毒抑制剂敏感性和病毒复制适应性的影响进行了表征。单一耐药替代（IN中的E92Q [IN-E92Q]、RT中的M184V [RT-M184V]和RT中的K65R [RT-K65R]）特异性地影响对相应抑制剂类别的敏感性，未观察到交叉类别耐药。IN-E92Q突变体对EVG的敏感性降低（50倍），添加RT-M184V或RT-K65R/M184V对此无影响。含有RT-M184V的病毒对FTC具有高水平耐药（>1000倍），添加IN-E92Q或RT-K65R对此无影响。在成对生长竞争期间，每个替代都导致病毒适应性下降，在无药物情况下，RT-K65R/M184V + IN-E92Q三重突变体适应性最差。然而，在接近生理水平的药物浓度存在时，耐药性抵消了复制缺陷，导致在存在一种药物时单突变体胜过野生型，在存在两种药物时双突变体和三突变体胜过单突变体。综上所述，这些结果表明，与RT和IN耐药替代相关的复制适应性降低和表型耐药是独立且累加性的。在存在多种药物时，尽管存在适应性缺陷，但具有多个替代的病毒的病毒生长更有利。
