Lenacapavir (Sunlenca®)

Last Update: 01 Jun 2026

Table of content

1. What Is It? 2. Risks 3. Benefits 4. Lactation 5. Key Takeaways 6. Research limits

Welcome to our Fact Sheet on lenacapavir during pregnancy and lactation. The information given is based on current research and may be updated with new scientific knowledge. This information does not replace personalized advice from healthcare professionals.

The Healthy Pregnancy Hub collaborates with the expertise of the CIHR Pan-Canadian Network for HIV and STBBI Clinical Trials (CTN+) in developing this information sheet.

CTN+ plays a central role in Canada’s response to HIV and other sexually transmitted and blood-borne infections (STBBIs). Through high-quality research conducted in partnership with communities, the network helps develop evidence-based solutions for people and regions affected by these infections.

1. What is lenacapavir?

Lenacapavir (Sunlenca®) is a medication used to treat and prevent HIV (human immunodeficiency virus). Lenacapavir can be given in two ways:

Tablet (by mouth):
The tablet is usually taken at the start of treatment before injections begin. This helps prepare the body for the medication.
Injection under the skin (subcutaneous injection):
After the first doses via tablet, lenacapavir is usually given as an injection once every 6 months by a healthcare professional.

Lenacapavir is a new type of HIV medication called a capsid inhibitor. It works by targeting an important part of the virus, which is the protective shell around the virus (called the capsid). This shell helps the virus function and multiply inside the body. By blocking the capsid, lenacapavir stops the virus from entering cell and spreading in the body which helps prevent and control HIV infection.

2. What are the risks of lenacapavir during pregnancy?

There’s no perfectly risk-free option when it comes to medication during pregnancy. If you are pregnant or planning a pregnancy, talk to your healthcare provider before starting, stopping, or changing any medication, including lenacapavir.

Lenacapavir is a new medication, so there is still very little research in pregnant people. Most of what we know so far comes from animal studies and a small number of human reports. As a result, there is not enough information on the safety of this medication in pregnancy or how pregnancy can impact the effect of the medication. For this reason, the Society of Obstetricians and Gynaecologists of Canada (SOGC) does not currently recommend lenacapavir (tablet or injection) as a first treatment option for pregnant people living with HIV.

In some situations, your healthcare provider may still consider lenacapavir. They can help you understand the possible benefits of preventing/managing HIV and risks for your specific situation so you can make an informed decision together.

Understanding risks during pregnancy

Every pregnancy starts with some risks. Problems like miscarriage (loss of the baby), birth defects (malformations present at birth), or premature birth (before 37 weeks) can happen in any pregnancy for many reasons. This is called the background risk. This means that some complications can happen even when no medication is taken. For example, birth defects occur in about 3 out of every 100 babies. When researchers study medications like lenacapavir, they compare outcomes with this background risk.

Because there is very limited research on lenacapavir in pregnancy, we do not yet know whether it affects fertility, miscarriage, or other pregnancy outcomes. So far, animal studies have not shown an increased risk of birth defects. But more studies in humans are needed to confirm whether the medication can be recommended in pregnancy.

The table 1 summarises what research has found so far. But one or two studies is not enough to confirm a risk. Many other factors like age, genetics, lifestyle, and health conditions can also play a role. If you have any concerns, talk to your healthcare professional who will help you make the best decision for you and your baby.

Table 1. Possible risks associated with taking lenacapavir during pregnancy.

Who?	What?	What does research say?
Pregnant person	Fertility (ability to get pregnant)	It is not known if lenacapavir makes it more difficult to get pregnant. One study looking at 193 pregnancies found no impact on fertility (Bekker et al., 2024). Animal studies in rats did not show effects on fertility, even at doses about five times higher than those used in humans tooltip. More studies are needed to better understand if there’s a risk.
Pregnant person	Miscarriages	So far, very few studies in pregnancy found no link between lenacapavir and the risk of miscarriage tooltip. More studies are needed to better understand if there’s a risk.
Unborn child	Congenital Malformations	Animal studies in rats and rabbits did not show birth defects, even at doses much higher than those used in humans. But there is still too little research in pregnant people to know if lenacapavir can increase the risk of birth defects.
	Growth	It is not known whether lenacapavir can increase the chance of having a baby with a low birth weight (less than 5 pounds 8 ounces [2,500 grams]). More studies are needed to better understand if there’s a risk.
	Premature Birth	Limited studies found no increased risk of preterm birth tooltip. More studies are needed to better understand if there’s a risk.
Child later in life	Brain development	It is not known if lenacapavir can affects a child’s learning, behaviour, or development. Animal studies have not shown harmful effects on development, even at doses much higher than those used in humans tooltip. More studies are needed to better understand if there’s a risk.
Fathers and sperm donors	Male’s fertility and pregnancy complications	No research has been done yet.

3. Asides from the risks, what are the benefits of lenacapavir?

Lenacapavir is a new HIV medication, and there is still limited research on its use during pregnancy. However, it offers some benefits in certain situations:

Long-acting treatment: Lenacapavir is given as an injection once every 6 months. This may be helpful for people who find it difficult to take a daily pill.
Prevention of HIV infection: Lenacapavir can help prevent HIV infection upon exposure.
Helping control HIV infection: Managing HIV during pregnancy is important because it helps lower the chance of passing HIV to the baby and your sexual partners while also being beneficial for your health.
An option when other HIV treatments are not working well: Lenacapavir may be used for people whose HIV is resistant to other medications, or when other treatments cannot be used because of side effects or safety concerns.

If you are pregnant or planning a pregnancy, talk with your healthcare provider. They can help you understand the possible benefits and risks and decide what treatment option is best for you.

4. Can lenacapavir affect breastfeeding or milk supply (lactation)?

Lenacapavir can pass into human milk, but the amount is expected to be very small. At this time, researchers do not know whether lenacapavir affects milk production or how it might affect a nursed baby tooltip.

In animal studies with rats, the medication was found in the blood of nursing pups. However, no harmful effects were observed in these studies.

Feeding decisions can feel emotional and personal. For people living with HIV, it’s important to have a discussion with your healthcare provider about feeding your baby. If breast/chest feeding is important to you, remaining on a traitement, like lenacapavir, can help minimise the risk of HIV transmission to the baby (less than 1%). In that context lenacapavir might be considered by your healthcare provider if the benefits of the treatment outweigh any theoretical risk.

If you have questions or worries, your healthcare team (midwife, nurse, doctor, nurse, pharmacist, lactation consultant) can help you the best option for your situation whether it is to feed your baby with human milk or with infant formula. Feeding support and resources are also available in your province or territory. All together, they can help you explore your options without judgment and support you in feeding your baby.

Key Takeaways

Lenacapavir (Sunlenca®) is a medication used to manage and prevent HIV.
Lenacapavir is a long-acting treatment given as an injection every six months, which may help some people who have difficulty taking daily medication.
There is limited research about the use of lenacapavir during pregnancy, so it is not usually recommended as a first treatment option during pregnancy.
Animal studies have not shown harm to the baby, but more studies in pregnant people are needed to confirm safety.
Lenacapavir can pass into human milk in small amounts, but we do not yet know how it may affect a breastfed baby.
Always discuss with your healthcare team before starting, changing or stopping oxazepam during pregnancy or while breastfeeding.

6. Research is great, but it is not perfect

Making informed health decisions during pregnancy also means understanding what research can tell us and what it cannot tell us yet. Research on HIV medications in pregnancy and lactation has helped us learn a lot, but it is still ongoing. There are some important reasons why research in this area has limits:

Not many large or long-term studies: There are fewer large studies that follow people over a long period of time, especially during pregnancy and after birth.
Limited information on long-term effects: We still do not fully know the long-term effects on a child’s development (such as learning or behaviour) or on the parent’s health. However, we do know that these medications have clear short-term benefits, including:
- reducing the chance of passing HIV to the baby
- improving the health of the pregnant and postpartum person
Pregnancy changes how the body works: During pregnancy, the body goes through many hormonal and physical changes. This can make it harder for researchers to know if a rare outcome is linked to a medication, the pregnancy itself, or other factors.
Lenacapavir is a new medication: Because it was approved only recently, there has not been enough time to collect large amounts of information about its use during pregnancy.
Few studies in humans: Most of what we know so far comes from animal studies or small studies in people. This makes it harder to know exactly how lenacapavir may affect pregnancy.

Because of these gaps, more studies are needed to fully understand how safe lenacapavir is during pregnancy. In the meantime, your healthcare provider can help you decide whether this medication is appropriate for your situation.

A big thank you to Iris Vendittoli, Sameer Kassim, Sarah Khan, and Sean Sinden for their expertise on the revision of this factsheet.

Other resources

References

National Institute of Child Health and Human Development. “Lenacapavir.” Drugs and Lactation Database (Lactmed), 2006, https://www.ncbi.nlm.nih.gov/pubmed/36701515.
Panel on Treatment of HIV During Pregnancy and Prevention of Perinatal Transmission. “Safety and Toxicity of Individual Antiretroviral Agents in Pregnancy: Capsid Inhibitors: Lenacapavir ” ClinicalInfo.HIV.gov June 12 2025 https://clinicalinfo.hiv.gov/en/guidelines/perinatal/safety-toxicity-arv-agents-capsid-inhibitors-lenacapavir-sunlenca
The Antiretroviral Pregnancy Registry Steering Committee. “Antiretroviral Pregnancy Registry Interim Report for 1 January 1989 through 31 January 2025.” 2025. U.S Food and Drug Administration. “Sunlenca® (Lenacapavir) Prescribing Information.” 2022.
Andrea Atkinson, Karen Tulloch, Isabelle Boucoiran, Deborah Money, Guideline No. 450: Care of Pregnant Women Living with HIV and Interventions to Reduce Perinatal Transmission, Journal of Obstetrics and Gynaecology Canada, Volume 46, Issue 6, 2024, 102551, ISSN 1701-2163, https://doi.org/10.1016/j.jogc.2024.102551. (https://www.sciencedirect.com/science/article/pii/S1701216324003748)
Linda-Gail Bekker et al., Twice-Yearly Lenacapavir or Daily F/TAF for HIV Prevention in Cisgender Women, N Engl J Med 2024;391:1179-1192; DOI: 10.1056/NEJMoa2407001; accessed https://www.nejm.org/doi/10.1056/NEJMoa2407001?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
Sarah Khan et al., Canadian Paediatric and Perinatal HIV/AIDS Research Group consensus recommendations for infant feeding in the HIV context, 2022, Journal of the Association of Medical Microbilogy and Infectious Disease Canada; retrieved https://www.ctnplus.ca/wp-content/uploads/2023/02/jammi-2022-11-03.pdf

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