NIH Discontinues HIV Vaccine Study
Vaccine regimen fails to prevent infection or reduce viral load (Apr. 25)
The National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), will stop administering injections in its HVTN 505 clinical trial of an investigational human immunodeficiency virus (HIV) vaccine regimen because an independent data and safety monitoring board (DSMB) found that the vaccine regimen did not prevent HIV infection or reduce viral load (the amount of HIV in the blood) among vaccine recipients who became infected with HIV.
The HVTN 505 study began in 2009 and was testing an investigational prime-boost vaccine regimen developed by the NIAID’s Vaccine Research Center. The phase IIb study was designed to determine whether the vaccine regimen could prevent HIV infection and/or reduce the viral load of vaccine recipients who became infected with HIV.
The investigational HIV vaccine regimen involved a series of three immunizations over the course of 8 weeks, beginning with a DNA-based vaccine designed to prime the immune system. The DNA priming vaccine contained genetic material that expressed antigens representing proteins from both the surface and internal structures of HIV. Immunizations with the priming vaccine were followed by a single injection at week 24 with a recombinant vaccine (the booster vaccine) based on a weakened adenovirus type 5.
The study enrolled 2,504 volunteers in the U.S. The study population consisted of men who have sex with men and transgender people who have sex with men. In its review, the DSMB examined the information gathered from 1,250 volunteers who received the investigational vaccine regimen and from 1,244 volunteers who received the placebo vaccine. The primary analysis looked at volunteers who were diagnosed with HIV infection after having been in the study for a minimum period of 28 weeks.
In the DSMB’s analysis, 27 HIV infections occurred among the vaccine recipients, and 21 HIV infections occurred among the placebo vaccine recipients. Among volunteers who became HIV-infected during the first 28 weeks of the study, 14 cases of HIV infection occurred among those who received the investigational vaccine regimen, and nine HIV infections occurred among the placebo vaccine recipients. Overall, from the day of enrollment through the month 24 study visit, a total of 41 cases of HIV infection occurred in the volunteers who received the investigational vaccine regimen, and 30 cases of HIV infection occurred among the placebo vaccine recipients.
In addition, the DSMB found that the vaccine failed to reduce viral load among volunteers who acquired HIV infection at least 28 weeks after entering the study and who had been followed for at least 20 weeks after diagnosis. Thirty participants (15 vaccine recipients and 15 placebo recipients) had measurable viral load.
Based on these findings, the DSMB recommended that no further vaccinations with the investigational vaccine regimen be administered.
Source: NIAID; April 25, 2013.