Marcia Frellick

February 12, 2016

BOSTON — Two phase 3 sister studies assessing the efficacy and safety of the dapivirine vaginal ring for the prevention of HIV-1 will likely be among the most-watched clinical trial results presented here at the Conference on Retroviruses and Opportunistic Infections (CROI) 2016.

Dapivirine is a potent antiretroviral known as a non-nucleoside reverse transcriptase inhibitor. It is thought that dapivirine prevents replication of the genetic material of HIV after the virus enters a healthy cell. Women wear the ring, which releases dapivirine slowly, for a month at a time, which makes it a discreet and easy-to-use method of protection.

Findings from the multination ASPIRE — A Study to Prevent Infection with a Ring for Extended Use — will be presented by Jared Baeten, MD, from the University of Washington in Seattle. And findings from The Ring Study will be presented by Annalene Nel, MD, chief medical officer of the International Partnership for Microbicides in Paarl, South Africa.

The two studies evaluated the ring in African women.

Controlling Replication

Control of the replication of HIV will be addressed by Bruce Walker, MD, from the Ragon Institute of Massachusetts General Hospital, the Massachusetts Institute of Technology, and the Harvard University Center for AIDS Research in Boston. His talk will focus on how the T-cell side of the immune system works.

"CD8+ T-cells are able to recognize virus-infected cells and kill them. We know that in some people, HIV replication is controlled without the need for medication for long periods of time," he told Medscape Medical News. "The overwhelming body of data indicates that this is through cytotoxic T-cells. Those become important in terms of thinking about a functional cure for HIV that could be effective in the setting of a vaccine or in the setting of a cure strategy."

"It's very clear that the various cure strategies may be able to mobilize the virus from reservoirs, but cells that start producing the virus don't die on their own. That has resulted in a refocusing of the field on the need for an effective CD8+ T-cell response to kill off those cells that become reactivated," Dr Walker explained.

Trends in Transmission

Recent trends in the transmission of HIV will also be explored at the conference. Infection in injection drug users, and specifically the 2015 outbreak in Indiana — which was reported at the time by Medscape Medical News — will be discussed by John Brooks, MD, a medical epidemiologist from the National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention at the Centers for Disease Control and Prevention.

In January 2015, health officials confirmed 11 new cases of HIV in a rural county in southeastern Indiana. Historically, fewer than five cases had been reported annually in the county. Most of the cases were linked to the sharing of syringes by people injecting the prescription opioid oxymorphone.

A coordinated response from county, state, and federal partners led to the identification of more than 180 new HIV infections, most occurring since mid-2014.

Although infections tied to injection drug use in the United States have declined steadily in recent years, prescription opioid abuse is rising sharply, which could increase the risk for HIV transmission, Dr Brooks told Medscape Medical News. Consequently, HIV infection is spreading among populations not previously considered to be at high risk.

"As clinicians and scientists, we must improve our understanding of the evolving epidemiology of HIV infection among these populations to prevent future outbreaks and rapidly respond if one should occur," he said.

Other Infections Highlighted

The primary focus of CROI will be HIV, but a host of other infections will also be examined.

A follow-up to last year's special session on Ebola has been added to the program in a "1-year-later" session. It is expected that information on the progress of two investigational vaccines, being evaluated in the PREVAIL — Partnership for Research on Ebola Vaccines in Liberia — study, will be presented, as will results from a randomized controlled trial of the antibody cocktail ZMapp for acute Ebola virus.

Hepatitis C made big headlines at recent CROI conferences with the discovery that new interferon-free drugs have cure rates near 100%. Achieving that success opens doors for new research.

"With hepatitis C now curable, I think the next frontier in liver disease in HIV-infected patients is hepatitis B," Chloe Thio, MD, an infectious disease specialist at Johns Hopkins School of Medicine in Baltimore, told Medscape Medical News.

As far as a cure, she said, "I don't think it's close."

Her talk will focus on what scientists know about the life cycle of hepatitis B and what they are beginning to understand about the immune response to hepatitis B.

"But with the virology and immune response, we still have a lot to learn," she reported.

Dr Thio reports receiving grant money from Gilead.

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