In vitro selection and molecular characterization of human immunodeficiency virus type 1 with reduced sensitivity to 9-[2-(phosphonomethoxy)ethyl]adenine (PMEA)

Antiviral Res. 1996 Oct;32(2):91-8. doi: 10.1016/0166-3542(95)00985-x.


9-[2-(Phosphonomethoxy)ethyl]adenine (PMEA) is an acyclic nucleotide with potent in vitro activity against human immunodeficiency virus type 1 (HIV-1). The present study was undertaken to determine whether HIV-1 resistance to PMEA could be generated by in vitro selection and if so, to determine which mutations in reverse transcriptase (RT) were responsible. HIV-1LAI was serially passaged for 10 months in the presence of increasing concentrations of PMEA up to a maximum of 40 microM. After 40 passages, the 50% inhibitory concentration (IC50) of PMEA had increased almost 7-fold from 4.45 to 30.5 microM. Some cross-resistance to 2',3'-dideoxycytidine (ddC, zalcitabine), 2',3-dideoxyinosine (ddI, didanosine), and 3'-thiacytidine (3TC, lamivudine) was also observed, but no cross-reactive resistance to 3'-azido-3'-thymidine (AZT, zidovudine). Sequencing of the RT encoding region of each of eight pol clones from resistant isolates revealed a Lys-65-->Arg (K65R) substitution. HIV with the K65R mutation inserted by site-directed mutagenesis also had decreased sensitivity to PMEA in H9 cells and a similar cross-resistance profile. Thus, HIV can develop decreased sensitivity to PMEA after long-term in vitro exposure and this change is associated with a K65R substitution. Additional studies will be needed to determine whether a similar mutation in HIV RT develops in patients receiving PMEA or its orally bioavailable prodrug adefovir dipivoxil (bis-POM PMEA).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives*
  • Adenine / pharmacology
  • Amino Acid Sequence
  • Anti-HIV Agents / pharmacology*
  • Cell Line
  • Drug Resistance, Microbial / genetics
  • HIV Reverse Transcriptase / genetics
  • HIV Reverse Transcriptase / metabolism
  • HIV-1 / drug effects*
  • HIV-1 / enzymology
  • HIV-1 / genetics
  • Humans
  • Molecular Sequence Data
  • Organophosphonates*
  • Point Mutation
  • Serial Passage


  • Anti-HIV Agents
  • Organophosphonates
  • adefovir
  • HIV Reverse Transcriptase
  • Adenine