HPTN 052: No Partner Infections with Viral Suppression
BETA is attending and reporting from the 2015 International AIDS Society Conference on HIV Pathogenesis, Treatment & Prevention this week in Vancouver—bringing you the latest news, updates, and research on HIV treatment and prevention.
Definitive and complete results of the HPTN 052 clinical trial were released yesterday at the 8th International AIDS Society Conference in Vancouver. HPTN 052 was a phase 3, large-scale, randomized controlled study comparing early versus delayed antiretroviral therapy (ART) and its effects on HIV transmission in serodiscordant, mostly (97%) heterosexual, couples. Final results revealed a 93% reduction in sexual HIV transmission within serodiscordant couples when the individual with HIV was taking ART.
“These findings demonstrate that antiretroviral therapy, when taken until viral suppression is achieved and sustained, is a highly effective, durable intervention for HIV prevention,” said Myron Cohen, MD, director of the Institute for Global Health and Infectious Disease at the University of North Carolina at Chapel Hill and principal investigator for HPTN 052.
HPTN 052 began in 2005 and enrolled over 1,750 serodiscordant couples at 13 sites in nine countries. The study completed its follow up in May of 2015. Over the course of the study, there were a total of 46 virologically-linked (i.e., verified by molecular testing) transmissions from the HIV-positive partner to the HIV-negative partner. Three transmissions occurred among couples who started ART immediately; 43 occurred in couples whose access to ART was delayed until the partner with HIV experienced a CD4 cell count decline below 250 cells/mm3. Eight people total were infected after their partner was taking ART. It is believed that none of the people who transmitted HIV to a partner were virologically suppressed at the time when the transmission occurred.
The estimate that early ART reduces transmission risk by 93% “may well underestimate the true power of [this] intervention,” explained Cohen. He says that half of the people who transmitted HIV to their partners while on ART did not have time to become virally suppressed before the transmissions happened. The other half were not virally suppressed because of treatment failure or because the participants were not taking ART as prescribed.
“No linked partner infections were observed when the HIV-infected index participant was stably suppressed on their ART,” he reiterated at the press conference.
Interim results of HPTN 052, shared publicly in 2011, showed a 96% reduction in HIV transmission with early ART transmission. These landmark findings were the first evidence proving that people with HIV who start ART early on in infection, before their CD4 cell counts drop below 250 cells/mm3, drastically reduce their risk of transmitting HIV to an uninfected partner.
At the time, the study’s Data Safety and Monitoring Board requested that results be made public but did not halt the study. Instead, participants in the delayed arm of the study—who were originally not eligible to receive ART until their CD4 cell counts dropped below 250 cells/mm3—were offered ART.
But uptake was gradual. “In the first year, when we offered ART to everyone in the delayed arm, 16% of people did not want to start treatment,” Cohen said at an IAS press conference. “How is that even possible in a clinical trial? Because they were so inculcated with messages that there’s no urgency. We’ve given them a whole generation of ‘Don’t worry about urgency of starting treatment because your CD4 count is what you’re paying attention to.’”
After five years, almost all (98%) of people with HIV in the study were on ART.
“These results have important implications for programs seeking to combine other HIV prevention measures with treatment as prevention,” said Cohen. “In the setting of such programs, special efforts should be made to minimize HIV transmission risk before viral suppression has been achieved, to maintain suppression on ART, and to identify and address ART failure.”