title: Phenotypic hypersusceptibility to non-nucleoside reverse transcriptase inhibitors in treatment-experienced HIV-infected patients: impact on virological response to efavirenz-based therapy.
abstract: BACKGROUND
  Enhanced susceptibility to non-nucleoside reverse transcriptase inhibitors (NNRTI) was recently described in association with increased resistance to nucleoside analogs (nucleoside reverse transcriptase inhibitors; NRTI).
  
  
  OBJECTIVE
  To determine the prevalence of NNRTI hypersusceptibility, the genotypic correlates, and its impact on virologic response to efavirenz-based salvage therapy.
  
  
  METHODS
  Genotype and phenotype testing was performed retrospectively on baseline isolates from 30 patients who received salvage therapy containing efavirenz. NNRTI hypersusceptibility was defined as a 50% inhibitory concentration (IC(50)) of < 0.5 that of the wild-type control.
  
  
  RESULTS
  Eight isolates had major NNRTI mutations. Among the 22 isolates with no major NNRTI mutations, 11 (50%) were hypersusceptible to efavirenz, 10 (45%) to delavirdine, and eight (36%) to nevirapine. Among eight isolates with NNRTI mutations, NNRTI resistance was present, but at lower than expected levels. The number of NRTI mutations was correlated inversely with the fold decrease in susceptibility to efavirenz (Spearman's rho, -0.57; P = 0.005), delavirdine (rho, -0.43; P = 0.04), and nevirapine (rho, -0.69; P < 0.001). Excluding subjects with NNRTI mutations, subjects with efavirenz hypersusceptibility at baseline had significantly better virologic suppression over 24 weeks than those without efavirenz hypersusceptibility (P < 0.001).
  
  
  CONCLUSIONS
  NNRTI hypersusceptibility is common in heavily treated but NNRTI naive patients and is related directly to NRTI resistance mutations. Among patients receiving efavirenz-containing regimens, NNRTI hypersusceptibility was associated with an improved virologic outcome after 24 weeks of therapy. A reversal of phenotypic resistance was seen in patients with NNRTI mutations in the presence of multiple NRTI mutations, but no obvious virologic benefit of this phenomenon was seen in this study.
authors: Stanford University School of Medicine, Stanford, CA 94305, USA.
authors: N
authors: N
authors: Shulman
authors: A R
authors: AR
authors: Zolopa
authors: D
authors: D
authors: Passaro
authors: R W
authors: RW
authors: Shafer
authors: W
authors: W
authors: Huang
authors: D
authors: D
authors: Katzenstein
authors: D M
authors: DM
authors: Israelski
authors: N
authors: N
authors: Hellmann
authors: C
authors: C
authors: Petropoulos
authors: J
authors: J
authors: Whitcomb
mesh_terms: D000480:Alkynes; D019380:Anti-HIV Agents / Q000627:therapeutic use*; D048588:Benzoxazines; D015331:Cohort Studies; D003521:Cyclopropanes; D004352:Drug Resistance, Microbial; D015658:HIV Infections / Q000188:drug therapy / Q000821:virology*; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics; D006801:Humans; D016296:Mutagenesis; D009705:Nucleosides; D010078:Oxazines / Q000627:therapeutic use*; D010641:Phenotype; D012189:Retrospective Studies; D018894:Reverse Transcriptase Inhibitors / Q000627:therapeutic use*
chemical_list: D000480:Alkynes; D019380:Anti-HIV Agents; D048588:Benzoxazines; D003521:Cyclopropanes; D009705:Nucleosides; D010078:Oxazines; D018894:Reverse Transcriptase Inhibitors; C098320:efavirenz