The International AIDS Vaccine Initiative (IAVI) and the St. Stephen’s AIDS Trust at the Chelsea and Westminster Hospital have initiated a Phase I clinical trial in London, UK to test a prime-boost combination of two HIV vaccine candidates.
“Prevention is crucial in the fight against HIV and AIDS, and a vaccine is one of the most powerful prevention tools we know to combat infectious diseases,” said Professor Brian Gazzard, Research Director at the St. Stephen’s AIDS Trust and the principle investigator of this trial. “We hope this trial will contribute to a better understanding of how to induce with a vaccine an immune response to protect against HIV infection and AIDS.”
The news follows promising results recently announced by IAVI and partners for one of the two vaccine candidates to be tested, the MVA-based TBC-M4, which in a recent phase I trial generated modest immune responses in all volunteers who received the highest dose. According to Patricia Fast, Chief Medical Officer at the International AIDS Vaccine Initiative, “The responses observed with this vaccine candidate warrant further research to improve immune activation. We have learned from other studies that a prime-boost regimen has the potential to achieve just this.”
That is why the new trial will include a DNA-based vaccine candidate called ADVAX to prime the immune system. Previous Phase I studies with different DNA and MVA-based HIV vaccines in combination have shown that this prime-boost regimen was safe and well tolerated, and also able to generate enhanced immune responses when compared with the responses generated by either vaccine alone. The ADVAX vaccine candidate also offers economic value; it is relatively easy and cheap to manufacture, which makes it particularly appealing for use in the developing world.
A separate Phase I trial testing ADVAX and the MVA-based candidates in a prime-boost regime is planned for India. This trial would use a different mode of administration for the priming vaccine, different dosages and different vaccine regimens. Collectively, the results of both trials will help determine whether further development of both AIDS vaccine candidates in a prime-boost combination is warranted.
Deborah Jack, Chief Executive of the National AIDS Trust, comments: “The UK has always been a leader in the quest for new technologies to prevent HIV. Hosting a vaccine trial in London is a great opportunity to continue doing our part in the global fight against HIV and AIDS. Like any medical development, discovering an HIV vaccine is a naturally long process but when a vaccine is found it could save millions of lives globally, not just in the developing world but also in the UK.”
About the vaccine candidates
The vaccine candidate TBC-M4 is based on a vector built from recombinant Modified Vaccinia Ankara (MVA). It was designed by a biotech firm in the U.S. in collaboration with Dr. Sekhar Chakrabarty from the National Institute of Cholera and Enteric Diseases (NICED) in Kolkata, India . It targets HIV-1 subtype C, the most predominant HIV subtype in India, and contains 6 HIV genes : env, gag, reverse transcriptase, rev, tat and nef.
The vaccine candidate ADVAX is a plasmid DNA vaccine containing HIV-1 subtype C genes env, gag, pol, nef and tat. The vaccine was designed by the Aaron Diamond Research Centre in New York, through collaboration with Rockefeller University in New York and the International AIDS Vaccine Initiative.
It should be noted that since both vaccine candidates contain only synthetic copies of part of HIV’s genetic material, they cannot cause HIV infection.
ADVAX will be administered with a needle-free device (Biojector 2000), and the trial will also assess whether this delivery mechanism provides benefits over regular injection with a needle and syringe. ”Needle-free injection of a DNA vaccine can provide enhanced immune responses compared with administration by needle and syringe,” according to Dr. Richard Stout, Executive Vice President and Chief Medical Officer of Bioject Medical Technologies Inc., manufacturer of the device.
About the trial
The trial is a Phase I randomized, double-blind, placebo-controlled trial. It evaluates the safety and immunogenicity of ADVAX and TBC-M4 vaccines in a prime-boost regimen. The trial is recruiting 32 volunteers who are healthy HIV-negative men and women at low risk for HIV infection. All volunteers must provide full informed consent for their participation in the trial.
In addition to using standard immunology assays to measure the responses following vaccination, the trial will also evaluate a novel viral suppression assay. This assay provides a functional assessment of the immune response by measuring anti-viral activity. “There are indications from previous clinical studies that the laboratory assays currently used in HIV vaccine clinical trials are not an accurate predictor of whether a vaccine can prevent or control HIV infection,” said Dr. Jill Gilmour, Senior Director of Clinical Research at IAVI. “We urgently need to identify which laboratory tests give us insight into whether a person will resist infection with HIV or development of AIDS. This will enable researchers to select the most promising vaccine candidates for large-scale efficacy testing.”
It is expected that the trial will take 14 months to complete. The trial is fully sponsored by the International AIDS Vaccine Initiative.
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