NIH stops HIV vaccine trial after immunizations fail

The federal government has put the brakes on the largest and most advanced study of a vaccine against HIV infection after an independent data and safety monitoring board found that the vaccine regimen did not benefit patients.

The HVTN 505 study, started in 2009 by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health, enrolled 2,504 volunteers--consisting of men who have sex with men and transgender people who have sex with men--at 21 sites in 19 U.S. cities. In a Phase IIb study, participants were given either a placebo or a series of three shots over an 8-week period, beginning with a DNA-based vaccine designed to prime the immune system. After 24 weeks, participants were then given a single booster injection based on a weakened adenovirus carrying genetic material that expressed a matching set of HIV antigens. An NIAID statement explained that the two investigational vaccines cannot cause HIV infection because neither contains live or weakened versions of HIV.

Conducted by the nonprofit HIV Vaccine Trials Network, the trial was meant to test whether the investigational vaccine regimen could prevent HIV infection, reduce the amount of virus in the blood of vaccine recipients who became infected with HIV, or both.

During a scheduled interim review on April 22, the independent monitoring board looked at data from 1,250 volunteers who received the HIV vaccine and 1,244 volunteers who received the placebo version. After being enrolled in the study for 24 months, the review board found that a total of 41 cases of HIV infection developed in volunteers who received the vaccine, and 30 cases of HIV infection occurred among the placebo recipients.

The board also found that the vaccine failed to reduce viral load--the amount of HIV virus in the bloodstream--among volunteers who got the HIV infection during the study.

Currently, the treatment regimen for HIV is costly, and patients must take daily pills like Gilead Sciences' ($GILD) Truvada to reduce the risk of infection over the course of their life. A vaccine to prevent the infection would be a breakthrough in HIV treatment.

The HVTN 505 trial is yet another upset in HIV prevention efforts. NIAID researchers said they will work with the HIV Vaccine Trials Network to analyze trial data and investigate why the vaccine did not work to help steer future vaccine endeavors. The researchers will continue to follow study participants for 5 years from the time of enrollment.

- here's NIH's official statement
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