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IMPAACT 2001 Primary Results Released

The IMPAACT Network is pleased to announce the presentation of primary results from IMPAACT 2001 study at the 2020 Conference on Retroviruses and Opportunistic Infections (CROI) today.


Primary results from IMPAACT 2001 were released 11 March 2020 at the Conference on Retroviruses and Opportunistic Infections (CROI).

IMPAACT 2001 was a prospective, open-label, multi-center study to evaluate the pharmacokinetics (PK) and safety of rifapentine (RPT) and isoniazid (INH) in HIV-1-infected and HIV-1-uninfected pregnant and postpartum women with latent tuberculosis (TB). This dosing strategy, also referred to as the 3HP regimen, consists of 12 once-weekly doses of RPT (900mg) and INH (900mg) taken with pyridoxine (25-100 mg).

Women are most likely to develop TB during or immediately after pregnancy, resulting in poor outcomes for themselves and their infants, making TB prevention very important in this population. A recently-completed randomized trial suggests that the TB drug regimen currently recommended by the World Health Organization (WHO) may increase the risk of adverse pregnancy outcomes, including low birth weight and stillbirth.

However, newer regimens, like 3HP, show fewer adverse events in non-pregnant adults and improved adherence; however, pregnant women have been excluded from these studies. IMPAACT 2001 aimed to provide data to extend the use of the 3HP regimen to pregnant women by examining its safety and PK.

The study enrolled 50 mother-infant pairs, including 20 mothers living with HIV, at five study communities in Haiti, Kenya, Malawi, Thailand, and Zimbabwe. All mothers who joined the study had a higher risk of acquiring TB symptoms (active TB) and were followed until 24 weeks postpartum. Mothers living with HIV also took an antiretroviral regimen consisting of efavirenz (EFV) and two nucleoside reverse transcriptase inhibitors (NRTIs) when they started the study.

Study Results

Primary results of the study showed that the blood levels of RPT were in the therapeutic range known to be effective in preventing TB. This means that mothers who are pregnant do not need to take a different amount of RPT compared to adults who are not pregnant. Results also showed there were no drug-related serious adverse events and no cases of active TB in mothers or their infants.

Among mothers without HIV, the blood level of RPT was somewhat higher during pregnancy compared to postpartum. This is because the body took a longer time to clear RPT from the blood during pregnancy (1.24 L/hr.) compared to after delivery (1.68 L/hr.). Among mothers with HIV, the blood level of RPT was the same during pregnancy and postpartum. However, the blood level during pregnancy was somewhat lower than in women who did not have HIV. These differences were not large enough to suggest that a different dose of RPT should be taken during pregnancy.

These results show that the 3HP regimen may help prevent mothers from acquiring active TB. Acknowledging this was a small study, research in larger studies is needed to learn more about the safety and effects of taking RPT and INH during pregnancy and after delivery. 

For more information about IMPAACT 2001, visit or contact