A single conservative amino acid substitution in the reverse transcriptase of human immunodeficiency virus-1 confers resistance to (+)-(5S)-4,5,6,7-tetrahydro-5-methyl-6-(3-methyl-2-butenyl)imidazo[4,5, 1- jk][1,4]benzodiazepin-2(1H)-thione (TIBO R82150)

Mol Pharmacol. 1993 Jan;43(1):11-6.


Tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione (TIBO) derivatives (e.g., R82150) are potent, human immunodeficiency virus-1 (HIV-1)-specific, inhibitors of reverse transcriptase (RT) that are undergoing initial evaluation in clinical trials. Because HIV-1 has become resistant to other RT inhibitors, we investigated the potential for viral resistance to TIBO R82150 by serial in vitro passage of HIV-1IIIB in the presence of drug. R82150-resistant variants (> 100-fold increase in IC50) dominated the replicating virus population after only three or four passages. R82150-resistant virus was partially cross-resistant to other HIV-1-specific RT inhibitors, including nevirapine (approximately 10-fold increase in IC50) and 1-[(2-hydroxyethoxy)methyl]-6-(phenylthio)thymine (approximately 3.5-fold increase) but remained susceptible to 2',3'-dideoxynucleosides and phosphonoformate. DNA sequencing of cloned resistant RT, combined with site-specific mutational analyses and construction of mutant recombinant proviruses, demonstrated that a single, conservative amino acid substitution (Leu100 to Ile) in HIV-1 RT is responsible for high level R82150 resistance and partial nevirapine resistance. These studies indicate that a subtle mutation in HIV-1 RT can dramatically affect viral susceptibility to an HIV-1-specific RT inhibitor. The clinical efficacy of TIBO derivatives and other HIV-1-specific RT inhibitors may be limited by the emergence of drug-resistant viral strains.

Publication types

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

MeSH terms

  • Antiviral Agents / pharmacology*
  • Base Sequence
  • Benzodiazepines / pharmacology*
  • Drug Resistance
  • HIV Reverse Transcriptase
  • HIV-1 / drug effects*
  • HIV-1 / enzymology
  • Humans
  • Imidazoles / pharmacology*
  • Molecular Sequence Data
  • Mutation
  • Phenotype
  • Proviruses / drug effects
  • RNA-Directed DNA Polymerase / chemistry
  • RNA-Directed DNA Polymerase / genetics
  • Reverse Transcriptase Inhibitors*
  • Structure-Activity Relationship


  • Antiviral Agents
  • Imidazoles
  • Reverse Transcriptase Inhibitors
  • R 82150
  • Benzodiazepines
  • HIV Reverse Transcriptase
  • RNA-Directed DNA Polymerase