Teenage men who have sex with men (MSM) adhered well to the daily regimen of Truvada (tenofovir/emtricitabine) as pre-exposure prophylaxis (PrEP) when monitored monthly in a recent study, but their adherence declined when switched to quarterly monitoring. They ultimately contracted HIV at a high rate. 

Results from the open-label ATN 113 study, which recruited participants ages 15 to 17 in six U.S. cities between August 2013 and September 2014, were presented at the 21st International AIDS Conference in Durban, South Africa (AIDS 2016).

PrEP is not approved in the United States for individuals under 18.

The study approached 2,864 MSM teens for the study. Participants were eligible if they reported behaviors that put them at risk for HIV during the six months prior. A total of 260 (9 percent) were eligible; 78 enrolled in the study. The participants had an average age of 16.5 years; 33 percent were mixed race, 29 percent were black, 21 percent were Latino, 14 percent were white and 3 percent were Asian or Pacific Islanders.

The participants made study visits at the beginning of the study and then monthly through week 12 and quarterly through week 48. The participants received behavioral risk reduction counseling and support to promote adherence to Truvada, which they were instructed to take daily.

At the outset of the study, 15.4 percent of the participants were diagnosed with and treated for sexually transmitted infections (STIs). During the study, 12.3 percent of participants were diagnosed with STIs at week 24, and 10.6 percent were diagnosed with STIs at week 48.

A total of three participants contracted HIV during the study, for an HIV infection rate of 6.41 percent per year.

A majority of the participants reported condomless sex throughout the study. The researchers did not find an association between condomless sex and adherence. Those who were nonadherent were significantly more likely to report being worried that people would think they were HIV positive if they saw their Truvada pills, compared with those who adhered well.

Overall, adherence dropped considerably once the study switched from monthly to quarterly clinic visits. At weeks 4, 8, 12, 24, 36 and 48, the proportion of the participants who took at least four tablets of Truvada per week according to dried blood spot testing was a respective 60 percent, 52.4 parent, 55 percent, 31.5 percent, 22.7 percent and 28.21 percent. Previous research has found that taking Truvada four or more times per week confers maximum protection against HIV. Adherence rates were not significantly different based on the race of participants.

Previously, the ATN 110 study of PrEP among 18- to 22-year-old MSM found moderate adherence among the group but also saw adherence drop over time. Adherence among black and mixed-race participants in that study was very poor.

The researchers in the new study concluded, “Regulatory approvals for youth under 18 are required to foster support for youth-friendly settings that will optimize PrEP use.”

Sybil G. Hosek, PhD, s clinical psychologist at Stroger Hospital of Cook County in Chicago and the study's head researcher, stresses that the initial adherence levels among the partcipants were actually remarkable for their age—95 percent had detectable drug levels during the first 12 weeks of the study—and that the drop-off in adherence once the study switched to quarterly monitoring was not a surprise to her.

"Adolescents need to feel connected and three months can feel like a lifetime," she says. "We need to do better by providing them with the time and attention they need to do PrEP well. Oral PrEP won't work for all youth, just like it won't work for all adults. But for some it will be a perfect fit."

Green signifies daily adherence, light green four or more pills per week, yellow two to three days per week, orange is less that two tablets, and red is totally nonadherent. The black line shows the proportion taking four or more doses per week.Courtesy of Sybil Hosek, PhD, Department of Psychiatry, Stroger Hospital of Cook County