VaxGen trials continue

Julian Meldrum
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This article is more than 23 years old.

As predicted by aidsmap last month, the two AIDSVAX efficacy trials will continue as planned after the first interim analysis of data from one of the trials.

(See VaxGen trials likely to go to full term.)

This month, the trials' independent Data and Safety Monitoring Committee had its first access to data on HIV infection rates, comparing recipients of AIDSVAX and those given a dummy vaccine in North America, Puerto Rico and Amsterdam. However, no data has been or will be publicly released before the end of the trials. Trial volunteers and clinicians remain blinded as to whether volunteers have received vaccine or placebo. This first trial will now conclude at the end of 2002; a separate Thai trial is due to end in 2003.

Glossary

placebo

A pill or liquid which looks and tastes exactly like a real drug, but contains no active substance.

efficacy

How well something works (in a research study). See also ‘effectiveness’.

blinding

When a clinical trial is blinded, the participants are unaware as to whether they are receiving the experimental drug or a placebo (or another drug). Double blinding refers to the participant, their doctor and researchers running the trial not knowing which treatment is received by each group until all data have been recorded. Blinding is done to reduce bias in clinical trials.

boosting agent

Booster drugs are used to ‘boost’ the effects of protease inhibitors and some other antiretrovirals. Adding a small dose of a booster drug to an antiretroviral makes the liver break down the primary drug more slowly, which means that it stays in the body for longer times or at higher levels. Without the boosting agent, the prescribed dose of the primary drug would be ineffective.

gp120

A glycoprotein on the HIV envelope. gp120 binds to a CD4 receptor on a host cell, such as a CD4 T lymphocyte (CD4 cell). This starts the process by which HIV fuses its viral membrane with the host cell membrane and enters the host cell.

The vaccines being tested may still prove entirely ineffective or they may be effective at a level well above the 30 per cent threshold the trials were designed to detect. VaxGen has declared its continuing optimism for its AIDSVAX gp120 products and has also announced plans to build a 99,000 square metre vaccine manufacturing plant on a business park site in Incheon, South Korea, which has been leased to the company for the next ten years, free of charge.

The decision to continue the VaxGen trials removes one uncertainty hanging over plans for two other trials, sponsored by the US National Institutes of Health and by the US and Royal Thai armies. These are also planning to test VaxGen’s products, as a booster for other vaccines designed and made by Aventis Pasteur.

Had VaxGen’s AIDSVAX turned out to be greatly more effective than expected, the current trials could have been terminated this month. Organisers of the other trials would then have needed to redesign them with AIDSVAX, rather than a placebo, as the comparison. This in turn would have required a larger number of trial volunteers, possibly ruling out the trials altogether.

(See 25,000 volunteers to be sought for vaccine trials.) Final decisions on these trials are due by the end of 2001.

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