VANCOUVER, British Columbia — Final 10-year results from the HIV Prevention Trials Network (HPTN) 052 study — in which the HIV-positive partner in a serodiscordant couple received antiretroviral therapy to protect the negative partner from HIV transmission — confirm the superb results reported at the interim analysis 4 years ago.
"These findings demonstrate that antiretroviral therapy, when taken until viral suppression is achieved and sustained, is a highly effective, durable intervention for HIV prevention," principle investigator Myron Cohen, MD, from the Institute for Global Health and Infectious Diseases at the University of North Carolina in Chapel Hill, said in a statement.
"The results are very compelling," agreed Julio Montaner, MD, from the BC Centre of Excellence for HIV/AIDS and the University of British Columbia in Vancouver, Canada.
"Treatment prevents disease progression, death, and virtually 100% of HIV transmission. So the road for us going forward is very clear," said Dr Montaner.
The final study results were presented here at the 8th International AIDS Society Conference.
Trials Network Study
The phase 3 randomized HPTN 052 trial was initiated in 2005. Most of the study participants — 97% of the couples — were heterosexual. The HIV-infected partner was assigned to early antiretrovirals, when CD4 cell count was 350 to 550 cells/mm³, or to delayed treatment, when the CD4 cell count was 250 cells/mm³ or less.
In addition to treatment for the infected partner, couples were provided with condoms and targeted counseling.
In the interim analysis of 1171 couples, presented in 2011, viral transmission between partners was reduced by 96% in couples assigned to early antiretrovirals.
In the final intent-to-treat analysis, viral transmissions were reduced by 93% in the couples assigned to early treatment.
"We observed 46 virally linked HIV transmissions in the overall cohort," Dr Cohen reported. Linked infections were determined with molecular virology to ensure that the infection was acquired from the infected partner.
Fewer of these virally linked transmissions occurred in the early group than in the delayed group (3 vs 43).
However, an intent-to-treat analysis could underestimate the true power of an intervention such as early antiretrovirals, said Dr Cohen.
For example, all three transmissions in the early group occurred either shortly before or immediately after treatment was initiated, "suggesting that viral suppression was incomplete or antiretroviral therapy had failed," he said. "And no linked infections were observed when the HIV-infected index partner was stably suppressed with treatment."
There were 14 unlinked viral transmissions in the early group and 16 in the delayed group. "That's one out of every 300 couple-years," he said, "and they were equally distributed between the two arms."
Dr Cohen acknowledged that he is not 100% sure how physicians should counsel couples about the prevention of HIV transmission.
"There is no doubt in my mind that the infected person needs to start their antiretroviral therapy at the earliest possible point in time," he told Medscape Medical News. But just how much time needs to elapse before the HIV-infected partner is no longer contagious has not been established.
"We also need to ask, 'What about the partner?' How much assuredness can the partner have based on the data we presented?" said Dr Cohen.
Effectively, the data show that after linked viral transmissions caused by treatment failure or inadequate viral suppression were eliminated, "you end up with an 'as-treated' protection rate of 100%," he reported.
"If someone reliably takes their medications and remains suppressed, the risk of HIV transmission to their partner is very, very small," he said. "That, I think, we can state with confidence".
The HPTN 052 study was funded by the National Institute for Allergy and Infectious Diseases. Dr Cohen and Dr Montaner have disclosed no relevant financial relationships.
8th International AIDS Society (IAS) Conference: Abstract MOAC0101LB. Presented July 20, 2015.
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Cite this: Early Antiretrovirals Protect HIV Serodiscordant Couples - Medscape - Jul 22, 2015.