If you’ve ever wondered what the status of HIV vaccine research is thus far… wonder no more! We were lucky enough to receive an update from John Beal, who attended an HIV Vaccine Trials Network conference this past October. The Hope Clinic of the Emory Vaccine Center is a site of the HIV Vaccine Trials Network. Twice a year, the Network researchers and community gather to review the latest findings.
To understand a bit more about the findings, first – there are four phases of trials:
Phase I trial – This is an early clinical trial designed to study an experimental vaccine in humans. Phase I trials are generally small (less than 100 participants) and designed to see if the product is safe.
Phase II trial – This is an intermediate clinical trial for studying an experimental vaccine in humans. The goals of Phase II trials are usually to learn more about vaccine safety and to see if the vaccine generates an immune response. Phase II trials, which involve hundreds of participants, occur only after the experimental vaccine is shown to be safe in a smaller Phase I trial.
Phase IIb trial – A Phase IIb (or test-of-concept) trial is about finding out if the vaccine concept or the type of vaccine candidate being tested will be effective. A test-of-concept trial is not designed to establish the efficacy of a particular candidate but rather to help researchers decide if a candidate is worth testing in larger Phase III trials. These intermediate studies are also referred to as proof-of-concept trials. The number of volunteers required for such trials is smaller, around 2,000 to 5,000 volunteers, compared to over 10,000 for Phase III trials.
Phase III trial – This is an advanced clinical trial in humans designed to prove whether or not a vaccine is effective. Phase III trials involve thousands of participants and occur only after the experimental vaccine has successfully moved from a Phase I and Phase II trial.
So where do we stand today regarding HIV vaccine trials? Here are some of the conference highlights:
- The results of the Phase III Thai trial that showed for the first time some protective ability are still being analyzed to understand both how it worked and how to make the protection more effective and last longer.
- There are 6 new vaccine trials in the planning stages.
- There are currently 5 active vaccine trials.
Preliminary results for Dr. Harriet Robinson’s phase II vaccine candidate HVTN 205 were presented and shows promising results. This vaccine contains many of the elements of the Thai vaccine and is showing a stronger ability to prompt an immune response in early analysis. The vaccine has not been tested yet for efficacy which is the next step. Dr. Robinson was an early advocate of the theory that binding antibodies that would attach to the virus would be effective in stopping the virus. Current research is showing that in fact this does show potential. Additionally, a new version of Dr. Robinson’s Geovax vaccine, HVTN 094, is currently enrolling.
The Hope Clinic is one of the sites participating in the largest most anticipated phase IIb trials, HVTN 505. This is a trial enrolling 2200 men that expects to be fully enrolled by next May. The results of this study are hoped to be a further step toward understanding how to produce an effective vaccine. If the results are strong enough this could move to phase III.
A big change to the HIV Vaccine Trials Network is coming over the next few years. The HVTN focus for trials will shift to southern Africa. The Emory Vaccine Center and Hope Clinic will be combining with other sites in the US to establish partnerships with trial sites in Asia and Africa. For the first time, the Gates Foundation will be helping to fund two massive trials.
For more information about current HIV vaccine trials, check out the HVTN website: www.hvtn.org