- Biktarvy is a widely used HIV treatment, however, it has not been well studied in pregnancy
- Researchers monitored its use in 33 pregnant women living with HIV in Thailand
- Levels of study drugs fell during pregnancy, but remained sufficiently high to suppress HIV
HIV treatment (antiretroviral therapy; ART) is highly effective at suppressing the production of HIV. With ongoing regular medication-taking, ART keeps HIV suppressed. The use of ART during pregnancy combined with prenatal care helps pregnant people with HIV have healthy babies.
Links to guidelines on HIV and pregnancy appear at the end of this CATIE News bulletin under “Resources.”
A pill called Biktarvy contains the following anti-HIV drugs:
- bictegravir
- FTC (emtricitabine)
- TAF (tenofovir alafenamide)
Biktarvy was approved in Canada and many other high-income countries about five years ago. When new treatments for HIV are approved, they have usually been tested mostly in large numbers of non-pregnant adults. After approval, researchers conduct studies in pregnant people. Recruiting pregnant people for studies is not easy, as many mothers are cautious about the effect of medicines on the fetus and subsequent newborn. Consequently, studies of medicines in pregnant women with HIV tend to be relatively small.
Complex changes occur to many organ-systems during pregnancy. As a result, levels of some medicines can fall significantly (compared to the time before pregnancy), so doses may need adjustment. To find out if this was the case with Biktarvy, researchers did a study with the combination of bictegravir + FTC + TAF in pregnant women.
A team of researchers with Gilead Sciences (the manufacturer of bictegravir + FTC + TAF) and the Thai Red Cross recruited 33 pregnant women from three countries for a study. All participants received the study drugs (one pill of Biktarvy once daily is the standard dose). Researchers took blood samples at regular intervals during pregnancy and for up to 16 weeks after birth.
The researchers found that levels of the medicines in Biktarvy were lower during pregnancy than after the women gave birth. Even so, the concentration of bictegravir (a powerful anti-HIV drug) remained relatively high and, combined with FTC and TAF, was sufficient to have the women maintain an undetectable level of HIV during and after pregnancy. No cases of treatment failure, virological resistance or transmission to infants occurred during the study.
Study details
Researchers recruited participants from the following three countries:
- Dominican Republic – 3 participants
- Thailand – 25 participants
- U.S. – 5 participants
One woman left the study after three days because she violated the study protocol (details were not released by the researchers).
Most of the women gave informed consent for blood samples to be taken from their infants (29 infants).
About trough levels
When analysis of the level of drugs in blood is done, scientists are particularly concerned with getting a sample of blood when drug concentrations are at their lowest. The lowest level of concentration of a drug is called a trough level. It is normal for drug levels to be somewhat low shortly before it is time to take the next dose of HIV treatment. However, if trough levels are too low, it is possible that HIV could develop the ability to resist the effect of treatment, ultimately leading to treatment failure.
Results
Overall, the concentration of drugs was lower during pregnancy than after birth. However, according to the researchers, the concentration was “[similar] to values for non-pregnant adults with HIV reported in other studies.”
Although trough levels of bictegravir were lower in the second and third trimesters compared to blood samples taken after birth, researchers found something interesting: Average trough levels of bictegravir were still sufficiently high as to exert anti-HIV activity (above 0.162 micrograms/mL).
Effectiveness
All participants maintained an undetectable viral load (in this case, less than 50 copies/mL) during pregnancy, the birthing process and after birth. CD4+ cell levels were stable during the study.
Blood samples from all 29 newborns who underwent testing were negative for the genetic material of HIV.
Safety
During pregnancy most adverse events were mild or moderate. Two people had more serious adverse events—fever and diabetes. However, these were not considered to be caused by Biktarvy.
One woman experienced what the researchers called “false labour” during the study. This was considered to be related to the study medicines. However, she subsequently had an uncomplicated pregnancy and birthing process and her baby was healthy.
The researchers did not find any increased risk for birth defects.
Another study by an independent team of researchers with 17 pregnant people who used bictegravir + FTC + TAF found broadly similar results to the present study. That study is continuing to recruit participants, so more results will be presented in the future.
Bear in mind
The researchers stated that the findings from this study “suggest that once-daily bictegravir + FTC + TAF without dose adjustment is appropriate during pregnancy.”
—Sean R. Hosein
Resources
Canadian HIV Pregnancy Planning Guidelines
REFERENCES:
- Zhang H, Hindman JT, Lin L, et al. A study of the pharmacokinetics, safety, and efficacy of bictegravir/emtricitabine/tenofovir alafenamide in virologically suppressed pregnant women with HIV. AIDS. 2024 Jan 1;38(1):F1-F9.
- Powis KM, Pinilla M, Bergam L, et al. Pharmacokinetics and virologic outcomes of bictegravir in pregnancy and postpartum. Conference on Retroviruses and Opportunistic Infections (CROI); Seattle, Washington. 2023. Poster 783.
- Pariente G, Leibson T, Carls A, et al. Pregnancy-associated changes in pharmacokinetics: a systematic review. PLoS Medicine. 2016 Nov 1;13(11):e1002160.