HIV Prevention: Discussing PrEP, PEP, and Vaccine Development
Colleen Kelley, MD, MPH, offers some insights on where we are today with the state of HIV prevention including the expanding PrEP options, why PEP is underutilized, and the challenges behind HIV vaccine development.
Here is the first in a news series on the state of HIV today including prevention, funding, and newer modalities.
HIV prevention in the form of pre-exposure prophylaxis (PrEP) continues to be a highly effective method of reducing the risk of contracting HIV. According to the Centers for Disease Control and Prevention (CDC), PrEP reduces the risk of getting HIV from sex by about 99%, when taken as prescribed.1 CDC says there is less information about how effective PrEP pills are among people who inject drugs; however, it is reported that PrEP pills reduce the risk of getting HIV by at least 74% when taken as prescribed. Currently, PrEP injectables are not recommended for people who inject drugs.1
Long-Acting Injectables
One of the more exciting areas within PrEP is long-acting injectables. This modality is giving individuals new options to protect against infection. At this week’s CROI, investigators presented new data on these modalities for FDA approved and developmental PrEP. For example, ViiV Healthcare reported new data the long-acting injectable cabotegravir (Apretude) demonstrating its effectiveness in 3 years of real-world data. Right now this is the only long-acting injectable that is FDA approved.
Additionally, the investigational long-acting injectable, lenacapavir, has shown high efficacy in phase 3 trials for PrEP and has a PDUFA date for June 19.
Learn more: Gilead's Once-Yearly Lenacapavir Formulations Show Sustained Efficacy for HIV PrEP in Phase 1 Study
“Long acting injectables are a tremendous advancement, both for HIV prevention and treatment. So with respect to HIV prevention, we know that taking a pill every single day for the duration of the time where you may be exposed to HIV can be difficult for a lot of people,” said Colleen Kelley, MD, MPH, professor, Department of Medicine, Emory University School of Medicine. “We know that about half of people who start oral daily oral PrEP, stop it within the first year of taking it. And so what these long-acting injectables offer is the ability to have excellent HIV prevention without having to think about it, without having to take that pill every single day…and when you take daily oral adherence out of the equation, that's where we see these amazing efficacy results.”
PEP
One area that is not discussed very often is post-exposure prophylaxis (PEP). Kelley says there are 3 challenges around it including the availability of the medication, the duration of the regimen, and potential insurance hurdles.
“It's difficult to access…And they don't know where to get it. They may go to an emergency room, they may go to a clinic, and there's no guarantee that clinic or emergency room will even offer you post exposure prophylaxis in the United States—even though it's recommended,” Kelley said. “And then the second step of how do you get the medication? Does your insurance cover it? Do you need to enroll in a patient assistance program if your insurance doesn't cover it? There's just too many logistical hurdles.”
“The current recommended post exposure prophylaxis regimen is actually 28 days, and that's long for some people who may have had a single exposure to continue taking that medicine every single day for 28 days.”
Long acting injectables are a tremendous advancement, both for HIV prevention and treatment. —Colleen Kelley, MD, PhD
HIV Vaccines
Although there are HIV vaccines in development, there are no FDA-approved immunizations. Kelley says the primary challenges to developing such vaccines is the structure of HIV and the ability of the virus to hide away in the body.
“The human immune system makes a very strong antibody response to the SARS-CoV-2 virus, that then helped to attenuated people who had COVID from having severe disease,” Kelley said. That same thing cannot be said of HIV. The HIV antibodies that people get neither prevent them from acquiring HIV, nor prevent them from getting severe disease. And it's because of the structure of the virus, the way that it hides from our immune system, the various ways that it integrates into our cells and just lives there silently. These are all the reasons why we've not been able to create an HIV vaccine similar to the COVID vaccine.”
Although the traditional methodology of creating vaccines has not proven to be efficacious for HIV yet, there is a much newer approach that is starting to be studied for HIV vaccines that includes broadly neutralizing antibodies (bnAbs). The International AIDS Vaccine Initiative (IAVI) has been helping to drive this area of research.
“The origin of our work on a new approach to HIV vaccine design began with the discovery, beginning in 2009, of potent broadly neutralizing antibodies (bnAbs) from large cohorts of individuals living with HIV in Africa, India, Thailand, Australia, the UK, and the US. Researchers at IAVI’s Neutralizing Antibody Center (NAC), a partnership with Scripps Research, and partners isolated and studied these bnAbs, which develop in some people after they have lived with HIV for several years. Later, researchers showed in the lab that some of these bnAbs block HIV from infecting cells,” IAVI writes on its site.2
This approach in studying bnAbs was reported at this week’s CROI conference by ViiV Healthcare as it relates to HIV management as part of a comprehensive treatment strategy.
The ability to prevent HIV continues to evolve, but it remains to be seen if the significant strides made in HIV prevention will continue, especially in today’s governmental policy environment.
