NIH Halts AIDS vaccine trial

The U.S. National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH), has halted a phase 2b clinical trial, HVTN 505, evaluating a sequential regimen of two HIV vaccine candidates.

The decision was based on the outcome of an interim analysis that indicated the regimen is not likely to prevent HIV infection or suppress the amount of HIV in the blood of vaccine recipients who became infected with HIV.

“The [NIAID] decision to halt the phase 2b clinical trial, HVTN 505, which assessed two vaccines, was based on an attempt to find an effective vaccine for HIV and AIDS patients, and while the current clinical trials was not completed, it has the potential to yield new strategies for future vaccine development for this population,” said Abimbola Farinde, PharmD, MS, clinical staff pharmacist at Clear Lake Regional Medical Center, Webster, Texas. “Additionally, it signifies that progress is being toward the development of an effective vaccine for those who are infected with AIDS/HIV and were previously without appropriate immunization.”

The study was conducted by the HIV Vaccine Trials Network (HVTN) and funded by NIAID. The prime-boost regimen comprised a DNA-based vaccine candidate and an adenovirus serotype 5-based candidate, both developed by the Vaccine Research Center (VRC) of NIAID.

The HVTN 505 study enrolled 2,504 volunteers at 21 sites in 19 U.S. cities. The study population consisted of men who have sex with men and transgender people who have sex with men. In its April 22 interim review, the independent data and safety monitoring board (DSMB) examined the information gathered from 1,250 volunteers who received the investigational vaccine regimen and 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 a minimum of 28 weeks. This was done to enable enough time for the vaccine regimen to be given and to stimulate an immune response.

In this analysis, 27 HIV infections occurred among the vaccine recipients, and 21 HIV infections occurred among the placebo vaccine recipients. Among volunteers who become 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 9 HIV infections occurred among the placebo vaccine recipients. Overall, in the study 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.

Additionally, the DSMB found that the vaccine had 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. There were 30 participants with measurable viral load (15 vaccine recipients; 15 placebo recipients).