HIV drug resistance: continuing 3TC or FTC may reduce additional mutations after virologic failure due to M184V/I mutation, UK study finds.


  • Jo Whelan
  • Medical News
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The M184V/I mutation has historically been common in patients who experience virologic failure on regimens containing lamivudine (3TC) or emtricitabine (FTC). However, as well as reducing susceptibility to these drugs, the mutation also reduces viral fitness and increases susceptibility to tenofovir (TFV), zidovudine and stavudine. Therefore, 3TC/FTC is often continued in antiretroviral therapy (ART) regimens for patients in this situation.

This study analysed 2,597 UK patients with the mutation to investigate whether 3TC/FTC use is associated with viral suppression or the occurrence of additional major drug resistance mutations following the detection of M184V/I.

  • The use of 3TC or FTC was continued in 43.2% of patients at ART switch following the detection of the M184V/I mutation. From 2007 onwards, one of these drugs was continued in the majority of people. 
  • 3TC or FTC use did not appear to be associated with increased viral suppression, but there was inconclusive evidence that it may reduce the appearance of additional drug resistance mutations in people with M184V/I.
  • The most important predictor of success, other than baseline viral load, was full susceptibility to at least one drug in the new regimen.
  • 3TC was associated with reduced viral suppression in people on regimens without tenofovir.

Where high‐quality evidence exists for specific ART regimens, this should be used to guide decision-making on the use of 3TC or FTC in people with the M184V/I mutation, the authors advise.

The study was published on behalf of the UK HIV Drug Resistance Database and the UK Collaborative HIV Cohort and is available as Open Access.