Two studies presented at the 8th International AIDS Society conference in Vancouver, Canada offered a look at factors associated with adherence to PrEP in men who have sex with men (MSM). In an oral presentation, researchers with the HPTN 067 (ADAPT) study reported on three groups of HIV-negative individuals who were assigned to take Truvada PrEP on a daily, time driven (two times per week) or sex driven (one pill before and one pill after sex) basis and found that daily did better. A second study of a specialized text message adherence support was presented as a poster and found that participant responses to the text system were strongly correlated with blood levels of tenofovir, thus suggesting that text-based systems might help with adherence.
Daily Versus Intermittent Dosing
In the ADAPT study, MSM and transgender women were randomized to the three dosing arms described above in either Bangkok or Harlem in New York City, with 180 men in each city. A separate analysis of ADAPT in 180 heterosexual cisgender women is reported here. As there were only four transgender women in the Bangkok and Harlem sites combined it isn't possible to draw conclusions on this particular population.
In the Harlem site, background HIV incidence was incredibly high, with 12% already being HIV-positive at screening. The group enrolled was also quite young and diverse, with roughly one third under the age of 25 and 70% being black and 25% Latino. The Bangkok site also had a relatively high incidence (6%) and enrolled almost all Asian men, who were on average 31 years old and highly educated.
Adherence was measured by an electronic monitoring device and weekly calls. In those reporting sex in the last seven days, blood levels of tenofovir were also measured at 10 weeks after randomized dosing occurred and also if someone seroconverted.
In both cities adherence was better with daily dosing than with time or sex driven dosing, though the difference was greater in Harlem. In Harlem, adherence was 65% with daily, 46% with time-driven and 41% with sex driven. In Bangkok, the rates were 85%, 79% and 65% respectively. One reason given in the qualitative analysis for challenges with adherence with the sex driven dosing is that the post-sex dose needed to be taken two hours after sex. This proved quite challenging for people who wanted to hide their pill from a sex partner or who would literally fall asleep before the time to take the pill arrived.
Though previously researchers had hoped that intermittent dosing might reduce the risk of side effects, neither the time or sex driven dosing arms had reduced rates of side effects compared with daily dosing. Thus, at least in this study, time and event driven dosing appeared less appealing than daily dosing.
Text Messaging Reminders
A second study, funded by the California HIV Research Program (CHRP) and conducted in Southern California, analyzed data from 152 HIV-negative men MSM taking open label Truvada who received text messages through a system named individualized Texting for Adherence Building (iTAB). The iTAB system sent individualized messages to the participants and asked them to respond whether they took their most recent doses of Truvada.
People who reported "perfect" dosing were combined with those reporting "high" and compared with those reporting "moderate" dosing, and all were compared with actual tenofovir-disphosphate levels in dried blood spots (DBS), which allowed for analysis of dosing.
There was strong concordance between reported dosing and DBS. Participants with sufficient tenofovir in blood to indicate five or more doses per week were significantly more likely to report that they had taken their medication regularly. Factors associated with poorer adherence included Hispanic ethnicity, younger age and more drug use.
This study shows the utility of an individualized text message support system that could allow for enhanced adherence supports in those who report missed doses.
David Evans is Project Inform's director of research advocacy.