Real-World PrEP Use Protects Against HIV

Pam Harrison

July 23, 2014

MELBOURNE, Australia — Pre-exposure prophylaxis (PrEP) protects against HIV in men who have sex with men and transgender women in the real world, even without perfect adherence, open-label extension data show.

"A key finding of this study is that interest and uptake of PrEP is high," Robert Grant, MD, from the University of California at San Francisco, said at a news conference here at the 20th International AIDS Conference. "We found that 76% of these men and transwomen wanted and started PrEP when given the opportunity to do so."

"We also discovered that men who have sex with men and transwomen who were at high risk for acquiring HIV were more likely to take up PrEP and were more likely to adhere to it," Dr. Grant added.

The study results were presented at the meeting and simultaneously published online in the Lancet Infectious Diseases.

The study was open to men and transgender women who previously participated in the randomized iPrEx study and 2 other PrEP trials.

The 72-week open-label extension trial involved 1603 participants not infected with HIV, with an average age of 28 years. In all, 76% opted to start treatment.

Of the patients who chose not to take medication, about half expressed concern about adverse effects. Another quarter said they did not want the inconvenience of taking a pill every day.

At the end of 72 weeks, investigators found that the incidence of HIV was directly related to weekly pill intake. In the original iPrEx study, investigators found that PrEP consisting of emtricitabine and tenofovir reduced the incidence of HIV infection by 44% over a median follow-up period of 1.2 years (N Engl J Med. 2010;363:2587-2599).

Incidence Directly Related to Pill Intake

PrEP use was measured in dried blood spots, a sensitive biomarker of long-term treatment. None of the study participants who took 4 or more tablets a week became infected with HIV.

In contrast, if no drug was detected in dried blood spots, the incidence of HIV was 4.7 per 100 person-years.

If drug concentrations indicated that the user had taken fewer than 2 tablets a week, the incidence of HIV was 2.3 per 100 person-years; for those who took 2 or 3 tablets a week, the incidence was 0.6 per 100 person-years.

In patients with drug concentrations associated with 2 or 3 tablets per week, the risk reduction for HIV infection was 90%, the investigators report.

There was a highly significant difference in HIV incidence between patients who took at least 4 tablets per week and those who did not (< .0001).

"We recommend daily dosing of PrEP because we think that daily use allows for habit formation," Dr. Grant explained. Daily dosing also creates the highest drug levels, which provides somewhat of a cushion in case people miss a few doses, he added.

"We found that no one, either in the extension study or in the randomized phase of iPrEx, became infected with HIV if their drug levels indicated the use of 4 pills or more per week. This does show some forgiveness for an occasional missed dose, especially if people have previously been taking the drug consistently," Dr. Grant noted.

Risk-Taking Behavior

After adjustment for sexual behavior, the incidence of HIV was 49% lower in those taking PrEP than those who did not, and 53% lower than in patients in the placebo group of the randomized iPrEx study.

Dr. Grant pointed out that when people were given PrEP and told how safe and effective it is, "we would see the condoms come off and people would have more sexual partners."

In contrast, extension investigators observed a trend toward safer sexual behavior over time. Research presented here by K. Koester, from the Gladstone Institute of Virology and Immunology in San Francisco, suggests that taking PrEP creates a mindfulness around sexual activity, so people think more about what they want from their sex lives and how best to avoid the adverse consequences of certain sexual practices (abstract TUAC0102).

Some thought that the introduction of PrEP would drive people wild.

Dr. Grant suggested that this new kind of mindfulness could explain the observed trend toward safer sexual practices among PrEP users over time. That said, risky sexual behavior — notably receptive anal sex without condom use — decreased in PrEP users from 33% to 25% over the study period and in non-PrEP users from 27% to 20%. The difference in both groups was significant (< .01).

"The good news about our paper is that people wanted to give PrEP a try when given the chance," Dr. Grant told Medscape Medical News.

However, PrEP users only took 4 or more tablets per week for about one-third of the full 18-month follow-up, which Dr. Grant said he feels is consistent with human behavior.

"We know that people go on and off PrEP, depending on when they need it," Dr. Grant told Medscape Medical News. "People get into relationships where they can negotiate safety or they can decide in certain partnerships that they can use condoms. I think the goal here is to provide options."

These findings reinforce the recent recommendation from the World Health Organization to consider PrEP in men who have sex with men, said Stefano Vella, MD, vice-president of the scientific council of ANRS (Agence Nationale de Recherche sur le Sida) in Paris.

"Some thought that the introduction of PrEP would drive people wild," Dr. Vella explained. "This study proved that this was not true. So what is being presented here is very important."

This study "provides still more evidence that gay and bisexual men and transgender women want access to this safe and highly effective form of HIV prevention," said Jim Pickett, director of prevention advocacy and gay men's health at the AIDS Foundation of Chicago.

Moving forward, said Pickett, "we must increase awareness of PrEP among all who could benefit from it and overcome critical barriers to PrEP access, including misinformation, lack of provider training, and insufficient coverage from health insurance and other payor programs."

This study was sponsored by the National Institutes of Health. Gilead Sciences supplied the PrEP drugs used iPrEx OLE. Dr. Grant, Dr. Vella, and Mr. Pickett have disclosed no relevant financial relationships.

20th International AIDS Conference. Abstract TUAC0105LB. Presented July 22, 2014.


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