Antiretrovirals could protect high-risk groups against HIV infection
Prophylactic treatment with antiretrovirals offers partial protection against HIV infection, a study published online in the NEJM shows (23 November 2010).
Men and transgender women who have sex with men were treated with emtricitabine and tenofovir disoproxil fumarate combination therapy, in a single tablet dosage or placebo.
Over a median follow-up of 1.2 years, the drug combination reduced HIV infection rates by 44 per cent compared with placebo. Blood levels of the drugs correlated with the prophylactic effect seen: in the treatment group, the antiretrovirals were detected in 51 per cent of uninfected subjects and 9 per cent of HIV-infected subjects.
However, the protective effect was less than predicted, with 2.9 per of the treatment group becoming infected with HIV, and measured drug exposure was lower than reported pill taking.
Sheena Castelino, principal HIV pharmacist at Guy's & St. Thomas' NHS Foundation Trust, London, said the study was well conducted and “provides preliminary evidence that prophylactic antiretroviral treatment could provide additional benefit, alongside safe sex practices and education, in a specific high risk population”.
The study addresses an important unmet need in public health, since HIV is more prevalent in the study population than in other groups, she told PJ Online.
“However, the optimal regimen for pre-exposure prophylaxis has not been established and data from this [study] cannot be applied to other populations.
We would need to test [pre-exposure prophylaxis] in other populations and look at the impact on HIV drug resistance, the long-term safety and tolerance of the drugs and cost-effectiveness of this intervention.”
The impact of increased expectations of the benefit of the drug on safe sex practice would also have to be evaluated, she said.
She added that the difference between measured drug exposure and reported pill use suggests that adherence will be a big challenge in making pre-exposure prophylaxis work.
Study method and findings
A cohort of 2,499 HIV-seronegative men or transgender women from six countries, all of whom who have sex with men, were randomised to oral emtricitabine and tenofovir disoproxil fumarate (n=1,251) or placebo (n=1,248) once daily.
All participants had HIV testing and received risk-reduction counselling, condoms and diagnosis and treatment of sexually transmitted infections.
Ten people were found to be infected with HIV at enrolment, and 100 became infected during follow-up — 36 in the treatment group and 64 in the placebo group, a relative reduction in incidence of 44 per cent (95 per cent confidence interval 15–63; P=0.005).
In the treatment group, the drugs were detected in plasma or cell specimens of 51 per cent of seronegative subjects and 9 per cent of HIV-infected subjects (P<0.001).
Nausea was reported more frequently in the treatment group than in the placebo group (22 versus 10 events, P=0.04). Unintentional weight loss was also more common in the treatment group (34 versus 19 events, P=0.04).
Citation: The Pharmaceutical Journal URI: 11049307
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