Adhesion makes all the difference to the efficacy of pre-exposure prophylaxis (PrEP), it was19.ª Conference on retroviruses and opportunistic infections, in a presentation I heard today.
Data were presented in two PrEP trials (giving anti-HIV drugs).HIV HIV-negative people to prevent infection), which reported significantly different results last year.
In April of 2011, the FEM-PrEP study demonstrated that PrEP women HIV negative with tenofovir / FTC pills (Truvada) to avoid its contamination by HIV was completely ineffective: there was no difference in the incidence of HIV among women who took Truvada and women who were part of the control arm taking placebo.
In July of 2011, however, PrEP in the Partners Study demonstrated that the Truvada was effective in preventing HIV infection in 73% of respondents: heterosexual partners of different HIV status.
How can we explain why HIV-taking women taking anti-retroviral pills did not achieve the same index, the result was no protection against HIV infection in one study but prevented at least two out of three infections in another study? The difference, it seems, is that, in the PrEP of the PARTNERS study, adherence to study medication was much higher, considering that in FEM-Prep, despite counseling and support, less than half of the women took the medications. tablets for your PrEP regularly.
PrEP in the Partners study
The PrEP PARTNERS 4758 study involved serodiscordant couples in Kenya and Uganda; the HIV-negative partner was female in 38% of couples. This study had three arms: tenofovir with a daily pill, a study arm with tenofovir daily and placebo control group.
There were 17 infections in tenofovir participants, 13 Truvada and 52 in the placebo group. Overall effectiveness was 75% for those assigned to it Truvada and 67% for those who are assigned to tenofovir, at which confidence intervals (44% to 81% of tenofovir and 55% to 87% of Truvada) overlapping, so that the efficacy of the two regimens was the same statistically. The same was true of the observed efficacy in women (65%) and observed efficacy among men (70,5%).
Adhesion according to the tablet count of the medication used was 97%. The substudy (Donnell) compared to tenofovir levels in the 29 blood of the 30 people who became infected in the preparation for the two arms with levels in a random selection of 198 people who did not become infected.
Tenofovir was undetectable in the blood of 70% of people who were infected, but only 18% of people who had no undetectable levels of Tenofovir, indicating adherence to the "true" level of about 80% - and having a detectable level of tenofovir. in blood was associated with a 86% reduction in the risk of contracting HIV in people taking tenofovir and a 90% reduction in rates of Truvada.
The FEM-PrEP study
In the FEM-PrEP study, 2.056 HIV-negative patients, women in South Africa, Kenya and Tanzania, were randomized to take either a daily Truvada pill or a placebo. The study was discontinued when an analysis for interim findings found near a rate of HIV infection identical to the rate of HIV infection in the Placedo arm. There were 33 HIV infections in women taking Truvada and 35 in women on placebo; this translates into annual incidence rates of 4,7% and 5,0%, respectively. This 0,3% difference does not represent a statistically significant difference (0,94 risk ratio, IC 95% confidence interval 0,59 to 1,52, p = 0,81).
Study participants said they took 95% tablets of the time and adherence as measured by the tablet count was 85%. However, when drug levels tenofovir and FTC were measured in the blood of women attributed to PrEP with Truvada, researchers found that less than 50% of women who should have taken the drug had actually done this in the past 12 days, and less than 40% in the last 48 hours.
In infected participants, 26% had detectable levels of tenofovir in their blood, the last visit before testing for HIV positive, 21% on the visit they tested positive and 15% on both visits; the non-infected participants whose samples were taken on the same day of visit were 35%, 38% and 26%, respectively.
At FEM-Prep, there were five cases of antiretroviral drug resistance (all with the resistance mutation M184V FTC), four in the placebo arm. Two of the four cases in women attributed to PrEp with Truvada were expressly the cases of transmission of the virus that was already resistant to drugs and is not caused by women partially adherent to PrEP and became infected, while the other two are still under investigation.
There were two cases of resistance to antiretroviral drugs in PrEP partners, but in both cases these were people who enrolled while there was acute suffering from HIV infection: there were no cases of resistance to antiretroviral drugs between 74 infections post-randomization.
A common observation to both studies was that the only side effect was that it was noticeably different between the drug and placebo, nausea and vomiting. In partners with PrEP Truvada was associated with a modest increase in symptoms in the gastrointestinal tract in the first month and the FE-PrEP rates were also significantly higher. If this is enough to deter participants from continuing the tablets that are strongly motivated then we do not need further research.
Why are there differences in adhesion?
Jared Baeten and Lut van Damme, principal investigators of the PrEP and FEM-Prep partners, respectively, were asked why I found a much lower adherence to FEM-PrEP than in the PrEP PARTNERS study.
Baeten commented that they were very different from the populations. PrEP men and women had partners to define themselves as being in a stable relationship, stable enough to last for at least two years of study duration. The partners who have encouraged the wife to take their pills, and a qualitative study has already confirmed that many participants were seen preparing the medication because, despite the were an opportunity to preserve their relationships, in an effort imposed by different serological status.
He was asked why PrEP could be used in a couple, where it would be more logical for the HIV-positive partner to pay attention to their treatment. He said that the use of PrEP within the family can be the bridge in time between the positive partner and the start of treatment for their viral load become undetectable.
Van Damme said that FEM-PrEP women were very young and had high levels of sexually transmitted diseases (STDs). The first qualitative surveys showed that many do not believe they are at high risk for HIV, despite the high incidence in their communities. There was also a high pregnancy rate in the study, notwithstanding the reported high levels of oral contraceptive use, showing that low adherence to medications was not limited to Truvada. There was no evidence that participants were not sharing their pills with others and, contrary to the data initially proposed, the pregnancy rate was not higher in women in PrEP, discounting the theories that drug interactions and preparation of the menstrual cycle may have made women more vulnerable to HIV.
"What we have learned from this study is that risk perception and risk understanding are important motivators for people to use biomedical prevention methods," she concluded.
Dr. Sharon of the Microbicides Experimental Network commenting on conference preparation in rehearsals, said: “PrEP is very, very efficient if you use it very well.”
Posted in: 06 March of 2012 in A tale of two trials: how much adherence is in PrEP Translated by Claudio Souza on 09 in July of 2015. Reviewed By Mara Macedo
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