What’s new with PrEP? Research & innovation at IAS 2017
BETA is attending and reporting from the 2017 International AIDS Society conference on HIV Science this week in Paris, France from July 23 to 26—bringing you the latest news, updates, and research on HIV treatment and prevention.
Pre-exposure prophylaxis (PrEP) was a main focus of research and innovation at the IAS 2017 conference this year, as the HIV community wonders: How is this biomedical form of prevention impacting communities are risk for HIV? And, what new forms of PrEP might we expect in the coming years? Below, BETA brings you research summaries of “on-demand” PrEP, a long-acting injected form of PrEP and a study of STI rates in gay men taking PrEP.
Does on-demand PrEP work if you don’t take it very frequently?
Daily PrEP dosing is the only dosing regimen currently sanctioned in the U.S., although on-demand dosing is an option for PrEP users in Europe. Although the IPERGAY study results showed on-demand dosing to reduce risk for HIV infection by 97%, a question has remained about how effective on-demand dosing is for people who have sex—and therefore dose—less frequently. (In IPERGAY, the median number of pills taken by participants was relatively high: 15 per month).
To try to answer this question, Jean-Michel Molina and Guillemette Antoni presented results from a sub-study of people in IPERGAY who used on-demand dosing—but only those who used less than the median number of pills taken per month by people in the entire trial. Their analysis included 269 participants, with 134 person-years of follow up.
People included in the analysis had a median of 5 sexual encounters each month, and took a median of 9.5 pills per month. Molina shared at the press conference that 25% of people had less than two sexual encounters per month.
There were six HIV infections, all among people in the placebo group. Because there were zero new infections among people taking on-demand PrEP, the researchers estimate the relative risk reduction to be 100% for people who use infrequent PrEP. Molina did acknowledge the large confidence interval for their risk reduction estimate, due to the fairly small sample size of participants, but said that he believes “the evidence now supports this dosing regimen.”
Truvada is approved by the U.S. Food and Drug Administration to reduce the risk of HIV infection only when used daily.
Sexually transmitted infections and condomless anal sex on PrEP
In a session devoted to sexually transmitted infections (STIs), Jeffrey Parsons, PhD, Director of the Hunter College Center for HIV Educational Studies and Training, presented results from a study of STIs and PrEP use with men who have sex with men in the U.S. The study was designed to evaluate how (or if) men who have sex with men change their condom use with PrEP, and if there is any difference in the rate of STIs experienced between men taking PrEP and not taking PrEP.
A sample of 1,071 HIV-negative men who have sex with men from across the U.S. were recruited into an observational study. Every 12 months, participants were sent urethral and rectal self-testing STI kits with instructions on how to complete STI testing and mail samples to a lab. Participants also answered questions about their PrEP use and sexual behavior.
Over the two years of the study (which began in 2014), the number of people who took PrEP (and stayed on it, or discontinued it) rose, while the number who had never taken PrEP declined.
The prevalence of condomless anal intercourse was high at each time point (baseline, 1-year, 2-years) across all subgroups of participants (people taking PrEP, people not taking PrEP and people who discontinued PrEP).
Parsons reported that they also conducted a series of within-group analyses to look at how movement on and off of PrEP changes whether a person has condomless sex or experiences STIs. There was a significant increase in the rate of condomless anal sex with casual partners when men were taking PrEP compared to when they were not on PrEP. The presenter’s poster explains that “this effect of change on PrEP was particularly strong when looking at receptive CAS [condomless anal sex] with HIV-positive partners.”
They also found a “slight but not significant” increase in the odds of an STI diagnosis during visits when men were on PrEP and once they discontinued PrEP.
Explaining the study’s findings, Parsons said that an important take-away from the study is that “there are a lot of different types of gay and bi men, and we tend to lump them all together. There are some who go on PrEP to have a back-up for condom use, and they continue to use condoms primarily and then use PrEP as a secondary for condom failure. Some go on PrEP because they are already having condomless sex, and they want to continue or increase that. Some men who want to have condomless anal sex choose to go on PrEP as a way to be able to do that, and as a result they may be more likely to get STIs.”
At the end of his presentation, Parsons offered additional information from one of his recently completed studies that speaks to the results of the current study. He said that in a survey of PrEP users in New York, only 51% were given a rectal STI screen and 48% given a pharyngeal (throat) STI screen at their last PrEP appointment (94% gave a blood sample, and 88% a urine sample).
“What we’re seeing is that providers are not doing the full range of testing and screening for PrEP users. We think that’s an area where we really need to make some improvements.”
Cabotegravir injectable PrEP will need to be given once every two, not three, months
Cabotegravir, a novel integrase inhibitor with a long-half life and good resistance profile, is being investigated as a drug for long-acting PrEP. The idea is that people might be able to receive an injection once every few months instead of having to take a pill for PrEP every day.
The HPTN 077 study, presented at the conference this week, compared two doses to determine which might work in studies moving forward. (An earlier clinical trial of cabotegravir used as an injectable long-acting agent for PrEP revealed that the dosing regimen did not produce drug levels high enough to reach targeted levels of protection from HIV.)
HIV-negative men and women (a total of 199 people) at sites in Brazil, South Africa, Malawi and the U.S. were randomized to receive an 800 mg dose every 12 weeks, a 600 mg dose over 8 weeks, or placebo. The 800 mg dose is actually delivered as two, split 2-mL injections; the 600 mg dose is delivered as one single 3 mL injection.
Only one participant discontinued from the study because of an injection-related adverse event. Most participants reported mild or moderate pain from the injections, but overall Raphael Landovitz, MD, MSc, from the Center for Clinical AIDS Research & Education, described the overall safety of the study as “excellent.”
The 600 mg dose delivered every two months, but not the 800 mg dose delivered over three months, met target pharmacokinetic goals—in other words, the levels of the drug needed in the body to protect against HIV infection.
“These data are extremely supportive of moving forward into phase 3 efficacy studies with at-risk individuals with the 600 mg every eight week dose,” said Landovitz.