Synergistic inhibition of HIV-1 reverse transcriptase DNA polymerase activity and virus replication in vitro by combinations of carboxanilide nonnucleoside compounds

Biochemistry. 1995 Aug 15;34(32):10106-12. doi: 10.1021/bi00032a002.


The carboxanilides UC84 and UC38 are nonnucleoside inhibitors of both the RNA-dependent and DNA-dependent DNA polymerase activities of HIV-1 reverse transcriptase (RT). We have previously shown that UC84 and UC38 bind to the same site as nevirapine but interact with different RT mechanistic forms, with UC84 preferentially binding to the RT-primer/template complex and UC38 binding only to the RT-primer/template-dNTP ternary complex [Fletcher, R. S., et al. (1995) Biochemistry 34, 4346-4353]. Here we demonstrate that combinations of UC84 and UC38 inhibit RT DNA polymerase activity in vitro in a synergistic manner. This synergy was noted primarily in reactions containing high concentrations of primer/template and Km levels of dNTP substrate and was independent of both primer/template identity and the molar ratio of UC84:UC38. Combination indices were in the range of 0.4-0.6, indicating substantial synergy in the inhibition of RT activity. More importantly, combinations of UC84 and UC38 also showed a high degree of synergy in inhibiting HIV-1 replication in both MT-4 and cord blood mononuclear cells. We believe this to be the first example of synergistic inhibition of HIV-1 RT by combinations of structurally related nonnucleoside inhibitors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antiviral Agents / pharmacology*
  • Base Sequence
  • Benzoates / pharmacology*
  • Carboxin / analogs & derivatives*
  • Carboxin / pharmacology
  • Cell Line
  • Drug Synergism
  • HIV Reverse Transcriptase
  • HIV-1 / drug effects*
  • HIV-1 / enzymology
  • HIV-1 / physiology
  • Molecular Sequence Data
  • Nucleic Acid Synthesis Inhibitors*
  • Oligodeoxyribonucleotides
  • Reverse Transcriptase Inhibitors*
  • Templates, Genetic
  • Thiocarbamates / pharmacology*
  • Virus Replication / drug effects


  • Antiviral Agents
  • Benzoates
  • NSC 615985
  • Nucleic Acid Synthesis Inhibitors
  • Oligodeoxyribonucleotides
  • Reverse Transcriptase Inhibitors
  • Thiocarbamates
  • NSC 629243
  • Carboxin
  • HIV Reverse Transcriptase