Another indication for poor adherence comes from
the genotypic analysis. In patients in whom treatment
failed, emergence of genotypically documented
resistance was low (elvitegravir 27% vs raltegravir 21%)
compared with 68% for raltegravir in the BENCHMRK
trials,12 and it was most noticeable in the subgroup with
one active background drug. Since both elvitegravir
and raltegravir have a fairly low genetic barrier to
development of resistance,15 this fi nding suggests
that low concentrations of elvitegravir or raltegravir in
plasma lead to minimum selection pressure.
rates (p=0·015), suggesting decreasing adherence as
remaining treatment options increase. This paradoxical
virological response rate is, however, in stark contrast
to previous observations in similar trials with raltegravir
(BENCHMRK),12 etravirine (DUET),13 and maraviroc
(MOTIVATE).