This Existing Drug Shows 100% Success Rate for HIV Prevention

More than 35,000 people are newly diagnosed with human immunodeficiency virus (HIV) in the U.S. each year, but there are medications to lower the risk of contracting the serious disease. Now, there may be a new drug to help lower the risk of getting infected with the virus—and it’s already FDA-approved.

A phase 3 clinical trial found that lenacapavir, which is currently marketed under the name Sunlenca and used to treat existing HIV infections, prevented HIV infections in every trial participant.

“With zero infections and 100% efficacy, twice-yearly lenacapavir has demonstrated its potential as an important new tool to help prevent HIV infections,” Merdad Parsey, MD, PhD, chief medical officer of Gilead Sciences, which makes lenacapavir, said in a statement. “We look forward to additional results from the ongoing PURPOSE clinical program and continuing toward our goal of helping to end the HIV epidemic for everyone, everywhere.”

What Is Lenacapavir?

Lenacapavir is in a class of medications called capsid inhibitors. It targets the capsid, which holds the RNA of HIV and other proteins that HIV uses to enter and replicate in cells. The medication stops viral replication by keeping HIV from reaching the nucleus of an infected cell, as well as interfering with the production of the virus so that it can’t infect other cells.

Lenacapavir is a subcutaneous injection, meaning it’s injected under the skin. It’s administered just twice a year.

How Effective Is Lenacapavir at HIV Prevention?

This particular trial found that lenacapavir was 100% effective at preventing HIV in at-risk patients, which is a first for an HIV PrEP drug candidate. (PrEP, or pre-exposure prophylaxis, is a type of medication that people can take to lower the risk of getting HIV.)

The study enrolled more than 5,300 cisgender women and teen girls between the ages of 16 to 25 in South Africa and Uganda. Study participants received lenacapavir or one of Gilead’s daily oral PrEP drugs, Descovy or Truvada.

At the end of the trial period, no infections were detected in the more than 2,000 women who took lenacapavir. However, there were a small number of infections in the Descovy and Truvada groups—2.02 per 100 person-years for Descovy and 1.69 per 100 person-years for Truvada. (Person-years are the number of years people submit data. So, a study that followed 100 people for a year would contain 100 person-years of data.)

“The findings are quite impressive,” Thomas Giordano, MD, MPH, professor and section chief of infectious diseases at the Baylor College of Medicine, told Verywell. “It has been harder to find successful PrEP treatments for cisgender women living in low- and middle-income countries. A successful PrEP treatment for this population would be a big advancement since in sub-Saharan Africa, half of the HIV infections are in women, and in the U.S., about 20% of HIV infections are in women.”

While Descovy, Truvada, and Apretude are still good and effective options for HIV prevention, a drug that can be taken even less frequently could improve uptake.

“If lenacapavir were to be approved for HIV prevention, it would be significantly more convenient for patients than other available PrEP options, given the twice-yearly dosing,” Stacey Rubin Rose, MD, associate professor of infectious diseases at the Baylor College of Medicine, told Verywell. “The two oral PrEP options are taken once daily, while injectable cabotegravir is dosed every two months.”

Infectious disease expert Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, told Verywell that these are “important findings that will make state-of-the-art, easier-to-use medications the method of choice for PrEP.”

“There is a whole menu of options for HIV prevention that are now available,” Adalja said. “The key is making sure that those who are high risk are taking advantage of them.”