Selective pressure of a quinoxaline nonnucleoside inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) on HIV-1 replication results in the emergence of nucleoside RT-inhibitor-specific (RT Leu-74-->Val or Ile and Val-75-->Leu or Ile) HIV-1 mutants

Proc Natl Acad Sci U S A. 1996 Jan 9;93(1):34-8. doi: 10.1073/pnas.93.1.34.


The quinoxaline nonnucleoside RT inhibitor (NNRTI) (S)-4-isopropoxycarbonyl-6-methoxy-3-(methylthiomethyl)-3,4- dihydroquinoxaline-2(1H)-thione (HBY 097) was used to select for drug-resistant HIV-1 variants in vitro. The viruses first developed mutations affecting the NNRTI-binding pocket, and five of six strains displayed the RT G190-->E substitution, which is characteristic for HIV-1 resistance against quinoxalines. In one variant, a new mutant (G190-->Q) most likely evolved from preexisting G190-->E mutants. The negative charge introduced by the G190-->E substitution was maintained at that site of the pocket by simultaneous selection for V179-->D together with G190-->Q. After continued exposure to the drug, mutations at positions so far known to be specific for resistance against nucleoside RT inhibitors (NRTIs) (L74-->V/I and V75-->L/I) were consistently detected in all cultures. The inhibitory activities of the cellular conversion product of 2',3'-dideoxyinosine (ddI, didanosine), 2',3'-dideoxyadenosine (ddA) and of 2',3'-didehydro-3'-deoxythymidine (d4T, stavudine) against these late-passage viruses were shown to be enhanced with the L74-->V/I RT mutant virus as compared with the wild-type (wt) HIV-1MN isolate. Clonal analysis proved linkage of the codon 74 and codon 75 mutations to the NNRTI-specific mutations in all RT gene fragments. The nonnucleoside- and nucleoside-resistance mutation sites are separated by approximately 35 A. We propose that the two sites "communicate" through the template-primer which is situated in the DNA-binding cleft between these two sites. Quinoxalines cause high selective pressure on HIV-1 replication in vitro; however, the implication of these findings for the treatment of HIV-1 infection has yet to be determined.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Antiviral Agents / pharmacology*
  • Base Sequence
  • DNA Primers / chemistry
  • Drug Resistance, Microbial
  • HIV Reverse Transcriptase
  • HIV-1 / growth & development*
  • Molecular Sequence Data
  • Mutation
  • Quinoxalines
  • RNA-Directed DNA Polymerase / genetics*
  • Reverse Transcriptase Inhibitors / pharmacology*
  • Selection, Genetic
  • Virus Replication / drug effects*


  • Antiviral Agents
  • DNA Primers
  • Quinoxalines
  • Reverse Transcriptase Inhibitors
  • HIV Reverse Transcriptase
  • RNA-Directed DNA Polymerase
  • HBY 097