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IMPAACT 2009 PK Results Released

9 March 2020

The International Maternal Pediatric Adolescent AIDS Clinical Trials (IMPAACT) Network is pleased to announce the presentation of results from the Pharmacokinetics (PK) Component of IMPAACT 2009, Pharmacokinetics, Feasibility, Acceptability, and Safety of Oral Pre-Exposure Prophylaxis for Primary HIV Prevention during Pregnancy and Postpartum in Adolescents and Young Women and their Infants, at the 2020 annual Conference on Retroviruses and Opportunistic Infections (CROI). A NIAID news release related to the presentation is available here.

Adolescent girls and young women experience elevated rates of HIV acquisition and this risk increases during pregnancy and following delivery. HIV pre-exposure prophylaxis (PrEP), in the form of oral FTC/TDF, can effectively reduce HIV acquisition; however, it is understudied in pregnant and postpartum populations.

IMPAACT 2009 is a two-part trial evaluating the feasibility, acceptability, and safety of oral PrEP in pregnant and postpartum adolescents and young women (16 to 24 years of age) in sub-Saharan Africa. The first phase of this study, the PK Component, characterized the PK of tenofovir during pregnancy and postpartum, and established tenofovir-diphosphate (TFV-DP) benchmarks for adherence monitoring in the second phase.

PK Component Results

Forty adolescents and young women ages 16 to 24 years enrolled at sites in Malawi, South Africa, Uganda, and Zimbabwe. Half of the participants were pregnant at 14 to 24 weeks gestation, and half had given birth six to 12 weeks prior to enrollment. Daily FTC/TDF was administered under direct observation for 12 weeks. With intense support from highly trained and experienced study staff, the women collectively took over 99% of their required daily PrEP doses under direct observation. TFV-DP red blood cell concentrations were measured from weekly dried blood spot (DBS) samples.

Analysis of the PK Component results, presented by Peter Anderson on behalf of the IMPAACT 2009 protocol team, found that among adolescents and young women who took HIV pre-exposure prophylaxis (PrEP) daily, TFV-DP levels in dried blood spots were approximately one-third (31-37%) lower in those who were pregnant than in those who had recently given birth. This finding is consistent with other studies in pregnant women, when tenofovir was used either for HIV prevention (i.e., PrEP), HIV treatment, or hepatitis B treatment. PrEP drug levels in the pregnant African adolescents and young women in IMPAACT 2009 were also lower compared to levels found in men and non-pregnant, non-lactating women in analogous direct observation studies in the United States. These findings reinforce the importance of daily adherence to PrEP for pregnant adolescents and young women.

The substantially lower drug concentration found in dried blood spots from pregnant adolescents and young women in this study does not necessarily indicate a lower PrEP efficacy for this group, according to the IMPAACT 2009 investigators. Evidence collected to date across studies has demonstrated that, when taken as prescribed, PrEP is effective at reducing HIV acquisition. However, no studies have yet identified the TFV-DP level that is associated with HIV protection in women, regardless of pregnancy status, and additional research is needed to determine the level of protection that daily PrEP can provide this population. 

For more information about IMPAACT 2009, visit https://impaactnetwork.org/studies/impaact2009.asp or contact IMPAACTops@fhi360.org.

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Funded by the National Institute of Allergy and Infectious Diseases, the Eunice Kennedy Shriver National Institute of Child Health and Human Development, and the National Institute of Mental Health of the US National Institutes of Health, US Department of Health and Human Services.