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PAVE Gives Pause: Position Statement on the Proposed PAVE100A Vaccine Trial

May 30, 2008

Also available in Spanish on the website of Grupo de Trabajo sobre Tratamientos del VIH

New York, NY -- Treatment Action Group (TAG) Position Statement on the Proposed PAVE100A Vaccine Trial

The failure of Merck's adenovirus serotype 5 (Ad5)-based HIV vaccine to protect against infection or reduce post-infection viral load, combined with the evidence of potentially enhanced susceptibility to HIV acquisition among a subset of trial participants, has inevitably cast a cloud across the Ad5 candidate slated for use in the proposed PAVE100A Phase IIb efficacy trial. TAG recognizes and appreciates the work and commitment of researchers at NIH's Vaccine Research Center (VRC) who have developed the DNA and Ad5 HIV vaccine constructs, and their colleagues involved in PAVE100 who have collaborated in an effort to redesign the trial to ensure safety in the light of the data that emerged from the Merck vaccine trial (STEP/HVTN 502, hereafter referred to as STEP).

However, TAG has serious concerns regarding whether the PAVE100A trial should move ahead. It is now being described as a "discovery" trial, but it is important to lucidly articulate what the trial might discover in the context of the data from STEP.

What is the evidence that the VRC prime-boost approach might lead to an outcome better than STEP?

What is the evidence that argues against conducting PAVE100A?

TAG's Take on a Tough Call

As an organization that supports the scientific endeavor to cure and prevent HIV infection, we are reluctant to simply oppose PAVE100A without proposing more promising alternative approaches. But our view is that serious consideration should be given to abandoning plans for this particular clinical trial and Ad5 vaccine candidate in favor of supporting research to rapidly address two key issues:

  1. The use of an alternate vector or DNA approach for the boosting immunization that could be studied in a broader population.

  2. Inducing broader responses to proteins contained in the vaccine, particularly HIV-1 Gag.

Based on the information that is currently available to us, we feel that the uncertainties argue against spending human and fiscal resources on PAVE100A, and instead suggest focusing on improving T cell-based immunogens so they can be studied in a broader population with a greater chance of success.

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