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Wednesday 25th February 2015

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A game-changer: 86% fewer HIV infections in two PrEP studies

Sheena McCormack presenting the PROUD study results at CROI 2015. Photo by Liz Highleyman, hivandhepatitis.com.

The most exciting news from CROI concerns pre-exposure prophylaxis (PrEP), the use by HIV-negative people of antiretrovirals to prevent HIV infection.

Two studies of PrEP in gay men and trans women have demonstrated that the availability of PrEP reduced the rate of infection by 86%. This amounts to the highest effectiveness yet seen for PrEP and is superior to most other HIV prevention interventions. Extraordinarily, two separate studies which provided PrEP in very different ways found exactly the same level of effectiveness.

The PROUD study was conducted in England and the IPERGAY study in France and Canada. Both recruited men who have sex with men and trans women who were at elevated risk of acquiring HIV – they had multiple partners, condom use was inconsistent or irregular, rates of sexually transmitted infections (STIs) were high, many participants had needed post-exposure prophylaxis (PEP) before and recreational drug use was common. Participants were generally well-educated and in full-time employment.

Both studies were also designed to be pilot studies, in preparation for larger trials. The fact that each study has demonstrated such a high and statistically significant level of efficacy with a few hundred participants tells us both about how effective PrEP is and how high the rate of infection is in some groups of gay men in western countries.

But there were important differences between the studies.

The PROUD study in England asked participants to take a pill every day (containing tenofovir and emtricitabine, Truvada). Participants randomised to the control group did not receive a placebo, but knew that they would receive the pills after a one-year delay.

Jean-Michel Molina presenting the IPERGAY study results at CROI 2015. Photo by Liz Highleyman, hivandhepatitis.com.

The IPERGAY study tested – for the first time – the idea of ‘intermittent’ PrEP. Participants were told that they only needed to take the pill before and after sex – a dose in the 24 hours before anticipated sex, and then, if sex happened, two separate doses in each of the two days that followed. This approach may make adherence easier, reduce the cost of the intervention and limit side-effects. The pill used was also Truvada and those randomised to the control group received a placebo.

In the PROUD study, the rate of new HIV infections was 1.3% per year in the PrEP group and 8.9% in the control group. The difference between the two figures translates to an effectiveness of 86%.

In IPERGAY, the rate was 0.9% in the PrEP group and 6.8% in the control group, with the difference again translating to an effectiveness of 86%.

Between the two studies, five individuals randomised to receive PrEP acquired HIV. However, none were thought to be taking the tablets at the time – four had stopped attending appointments or were returning unused pill bottles to the clinic. The fifth person is thought to have acquired HIV just before beginning PrEP. 

Results are generally reassuring in terms of side-effects, drug resistance and sexual behaviour change.

Adherence proved to be very good in both studies, despite their very different dosing schedules. The PROUD study aimed to replicate ‘real-life’ clinic conditions in England and showed that fears of poor adherence in this setting were unfounded. The IPERGAY results show that gay men are capable of taking PrEP in a way that suits their lifestyle and maximises their safety.

Disappointing result for women's microbicide

Helen Rees at CROI 2015. Photo by Gus Cairns, aidsmap.com.

After the encouraging results on PrEP presented at CROI, there was one major HIV prevention setback. FACTS 001, a study testing the efficacy of a vaginal microbicide gel containing tenofovir, produced a null result. There was no difference in the HIV infection rate in young women given the gel and the rate in young women given a placebo gel.

While some other microbicide studies have previously reported disappointing results, they all asked women to use the microbicide every day. FACTS 001 was designed to test the effectiveness of intermittent use of a microbicide – women were asked to use the gel once before and once after having sex. The researchers aimed to replicate the findings of CAPRISA 004, the study which in 2010 raised hopes by finding that a tenofovir-based microbicide gel was 39% effective.

Just over 2000 South African women were recruited, making this a larger study than CAPRISA 004. With an average age of 23, the women were younger than in the previous study. Younger women are especially vulnerable to HIV but may have difficulties using prevention methods consistently.

The researchers put extra effort into community support and education programmes for trial participants, and this did improve adherence to some extent. The minority of women who were able to use the tenofovir gel on 80% of the occasions they had sex had 57% fewer infections.

But overall, adherence remained low. This meant that there was no difference in the rate of HIV infection between women given the tenofovir and placebo gels (4% each year in both groups).

This means that young, vulnerable women still lack HIV prevention methods which fit into their lifestyles and which they can actually use.

Triple-drug combination superior for preventing HIV in infants

Mary Glenn Fowler presenting at CROI 2015. Photo by Liz Highleyman, hivandhepatitis.com.

Implementing the World Health Organization (WHO) recommendation of three-drug antiretroviral treatment during pregnancy leads to a significantly lower rate of mother-to-child HIV transmission, a 7-country randomised study has shown. The PROMISE study was conducted in sub-Saharan Africa and India.

The study recruited 3529 pregnant women, who were generally in good health and would not otherwise have been eligible for antiretroviral treatment in their country. Their median CD4 cell count was 530 cells/mm3 and they were a median of 26 weeks into their pregnancy.

Some women were randomised to receive the WHO’s ‘option A’ – zidovudine from week 14 of pregnancy plus single-dose nevirapine at delivery. After delivery, women also received a 14-day regimen of tenofovir and emtricitabine in order to minimise the risk of nevirapine resistance.

Alternatively, women were randomised to receive ‘option B’, a triple-drug combination from week 14 of pregnancy and throughout the breastfeeding period. This was a protease inhibitor based regimen, including lopinavir and ritonavir. Depending on randomisation, the backbone was either zidovudine and lamivudine, or tenofovir and emtricitabine. (Since the study was set up, WHO guidelines have been updated to recommend an efavirenz-based regimen as option B.)

The rate of transmission was low in both groups, but significantly lower when a triple-drug combination was provided. The rates were 1.8% and 0.6% respectively.

In terms of safety, the triple-drug arm was associated with a higher risk of moderate adverse events or poor outcomes, including premature birth and babies being born with a low birth weight. However, there were no differences in terms of more severe outcomes.

Breastfeeding mothers in Africa need to be tested for HIV

There are high rates of undiagnosed HIV infection among women breastfeeding their babies in African countries, putting their infants at risk of acquiring HIV. The data come from 11,550 women who took part in household surveys conducted in three communities in Kenya, Malawi and South Africa. Women were asked about antenatal care that they had received and took HIV tests (including tests for recent infection) as part of the survey.

Although over 85% of women had taken an HIV test in antenatal care, the survey shows that many acquire HIV during their pregnancy or while breastfeeding. Four per cent of all women who were breastfeeding and had received an HIV-negative test result in antenatal care had acquired HIV by the time of the survey.

Moreover, women may drop out of care, with a resulting high viral load. Here the results differed by study site, with poorer results in Kenya (which offers pregnant women a short course of antiretroviral treatment, known as WHO’s Option A), compared to Malawi (which offers pregnant women lifelong antiretroviral treatment, option B+).

The researchers recommended repeat HIV testing during pregnancy and breastfeeding, with women being offered tests beyond the antenatal clinic, in child health and other settings.

Add your voice: Community statement on PrEP

NAM is one of the UK organisations supporting a joint statement, calling for the NHS to speed up access to PrEP (pre-exposure prophylaxis).

Other organisations (and individuals) are invited to show their support.

Visit www.prepaccess.org.uk

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