animation of a pill box opening each day to reveal only one pill per week

A Once-A-Week ART Trial with Lenacapavir and Islatravir

Research scientists are working together to see if a combination of medications - lenacapavir and islatravir - can improve HIV management. Both of these medications have a big advantage over current antiretroviral therapy (ART): they can be taken once a week, rather than daily.1

A new type of ART: capsid inhibitors

One drug is called lenacapavir. It is a new type of ART called a capsid inhibitor.1

A capsid is the outer protein coat of a virus. Like you need a key to open a locked door, HIV needs an intact coat in order to infect cells. So scientists believe that preventing the formation of a normal coat may stop the virus from getting into cells.2

Things to note about lenacapavir

Studies in the lab show that lenacapavir has some exciting characteristics:3

  • Causes HIV to form abnormal coats
  • Works against both HIV-1 (even against HIV-1 that is resistant to traditional ART) and HIV-2
  • Does not cause problems for human cells
  • Is effective in combination with other ART drugs

A small human study on lenacapavir

In a small human study, 81 percent of participants taking lenacapavir had a suppressed viral load.4

There were no major side effects. One of the biggest benefits of lenacapavir is that it has long-lasting effects, so it does not need to be taken as often. This medication can be given as an injection every 6 months.5

A clinical trial in progress

These are early results. The clinical trial is scheduled to continue for a full year of treatment and monitoring for even longer. It will not be completely finished until 2023.6

Results are not yet published in a scientific journal. This is important because, before publication, other scientists will double-check the information to make sure the results are accurate. Researchers continue to test lenacapavir with a couple of other studies starting soon.7

A combination study with islatravir

The second medication intended for a combination study with lenacapavir is islatravir. It inhibits reverse transcriptase, an enzyme that HIV uses to reproduce. Like lenacapavir, it is long-lasting and animal studies show that it works against ART-resistant strains of the virus.1,8,9

A study combining islatravir with doravirine did lower viral load in study participants, according to an October 2021 press release. However, some study participants also had lower T-cell counts. As a result, the FDA placed a hold on any further human testing of islatravir.10-12

A pause on enrollment

The researchers will keep monitoring these participants to see how they do overtime. As of November 2021, a temporary pause on the enrollment of participants was announced for the combination study.13,14

Study participants who have already started will continue with the weekly medication dose and will be monitored closely. This is why clinical trials are so important: our immune systems are complicated. Drugs that look great in the lab or even in animals may or may not work the same way in actual humans. This is especially true when different meds are used in combination.

A path for new antiretroviral options

ART that is available now has changed the lives of so many. New medications that streamline treatment or target drug-resistant strains would help millions of people living with HIV. Clinical trials like these - with scientists from different companies working together - are getting us a step closer to new options.


Dr. Audrey Sheridan is a board-certified obstetrician-gynecologist (OB-GYN) and also a caretaker for her dad. Dr. Sheridan is inspired by people finding their way through life-changing medical situations with resilience and is interested in how we can increase our mental durability in the face of the unpredictable.

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This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

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