The first major clinical trial began Tuesday for an injectable drug to prevent HIV.



The drug, cabotegravir, is already used to treat people who have been infected by HIV, but is being tested for the first time as a way to prevent transmission of the virus, in what is known as pre-exposure prophylaxis (PrEP). The drug would be injected once every eight weeks, and if effective, will be made available as an alternative to the only other form of PrEP currently on the market, the once-a-day blue pill Truvada.

No vaccine for HIV exists, despite decades of study. But Truvada has been shown to be roughly 99% effective in preventing new infections, for those able to stick to its once-a-day regimen.

But not everyone is able to maintain the daily habit. “While a daily medication may be great for a number of folks, other people may have challenges adhering,” Albert Liu, research director of the HIV prevention program at the San Francisco Department of Public Health, told BuzzFeed News.

In a 2015 study, Liu tested adherence rates among 557 men who have sex with men and transgender women in San Francisco, Miami, and Washington D.C. Roughly 80% to 86% of the study participants showed high enough levels of the drug in their blood to protect them from HIV.

Among those who had lower levels were people with unstable housing and black men. Other studies have shown that adherence is also lower among younger people. HIV diagnoses in the US are currently highest among black gay men.

In 2015, more than 39,000 people were diagnosed with HIV infection in the US.

“As simple as it might sound for some people, some people just don’t like the idea of taking a pill every day,” Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, told BuzzFeed News. “Everything from the inconvenience of it, as well as just the psychological aspect of having to take a pill every single day.”

Privacy issues too, particularly among groups for whom homosexual behavior may be more stigmatized, also play into the ability to stick with a once-a-day pill regimen.

The new trial will enroll 4,500 men who have sex with men and transgender women at 45 sites in eight countries to see whether a group that is given a cabotegravir injection every two months and takes placebo pills achieves comparable protection from HIV to a group who is given Truvada and a placebo injection. The dual placebo design of the study ensures that participants receive some form of preventive medicine. The investigators hope to study the participants for over four years and release the results by 2021.

If it’s effective, the two-month injection will be the only new drug approved to prevent HIV transmission since Truvada was approved in 2012.

“I think having more available prevention options for people will be really critical,” said Liu.

“It’s similar to contraception — where there are a variety of different options for women who are seeking birth control,” he continued. “Having a range of options for HIV prevention will also be enormously helpful to bringing down new cases of HIV.”