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Tuesday, March 6, 2012

Plasma drug levels as markers of adherence in PrEP

PRN Report from 19th CROI:

In the Partners PrEP study of HIV serodiscordant heterosexual couples in Kenya and Uganda, blood plasma levels of PrEP medications seronegative partners were investigated as a biological marker of adherence to PrEP and a predictor of protective efficacy.

Deborah Donnell, of the Fred Hutchinson Cancer Res Center in Seattle, reported on this case-cohort study comparing TDF drug levels in patients who acquired HIV-1 to a cohort who did not acquire HIV-1. Cases were those from the TDF and FTC/TDF arms who acquired HIV-1 after randomization (n = 17 for TDF; n = 12 for FTC/TDF); plasma from the HIV-1 seroconversion visit was tested. The comparison cohort was 198 randomly selected subjects from the TDF and FTC/TDF arms; plasma from months 1, 3, 6, 12, 18, 24, 30, and 36 was tested (n = 902 samples). TDF, the common medication between the 2 active study arms, was tested.

For those randomized to TDF, having a detectable level of TDF, as compared to an undetectable level, was associated with an 86% (95%CI 67% to 94%, p <0.001) reduction in HIV-1 risk; for the TDF/FTC arm, the HIV-1 risk reduction was 90% (95%CI 58% to 98%, p = 0.002). Thus, detection of TDF in plasma was strongly predictive of high protection from HIV-1 acquisition. Drug detection and levels over multiple visits in the control cohort suggest that a majority consistently used PrEP, supporting the high level of protection for HIV-1 acquisition observed in the Partners PrEP Study.

Donnell D, Baeten J, Hendrix C, Bumpus N, et al. Tenofovir Disoproxil Fumarate Drug Levels Indicate PrEP Use Is Strongly Correlated with HIV-1 Protective Effects: Kenya and Uganda. Presented March 6, 2012 at the 19th CROI, Seattle, WA. Oral Abstract #30.

Source: Reporting from Seattle for PRN News: James Braun, DO