The 13th World AIDS Conference in Durban, South Africa, is expected to draw some 10,000 researchers, activists and reporters, offering a high-profile venue to release information about products in development. VaxGen Inc. and Chiron Corp. were among those seizing the opportunity in the opening days of the conference, which runs through Friday.

As previously reported, VaxGen, of Brisbane, Calif., has taken two versions of a preventive vaccine called AIDSVAX into Phase III trials. One version, AIDSVAX B/E, is tailored for the types of HIV circulating in Southeast Asia and the Pacific Rim and is undergoing a 2,500-patient Phase III study in Thailand. The second Phase III is testing AIDSVAX B/B in North America and Europe against the types of HIV predominant in those regions.

The Thailand trial is enrolling injection drug users in Bangkok. Participants are mostly male (average age 30.6 years) and 30 percent have reported sharing needles. Thus far, retention and immunization compliance have been excellent.

In the U.S. trial, the company has enrolled at-risk volunteers who are primarily men (94 percent), white (83 percent) and educated. Baseline sexual behavior for men who have sex with men indicates that 54 percent had five or more sexual partners and 44 percent had HIV+ partners in the last six months. So far, retention has been excellent and there have been no serious adverse events related to the vaccine.

As part of its trial protocols, VaxGen is monitoring social harms, such as stigmatization of volunteers or an increase in risk-taking behavior. To date, most of the social harms reported have been resolved, and there is no trend toward increasing risk behavior among the volunteers.

An interim analysis for efficacy in North American trial volunteers is slated for 2001. If the product is at least 30 percent effective in reducing HIV infections, VaxGen plans to submit an application for regulatory approval.

VaxGen's (NASDAQ:VXGN) shares closed Monday at $25.06, up 56 cents.

Chiron Corp. reported Phase II data showing recombinant interleukin-2 boosts the effects of standard antiretroviral therapy in patients with HIV infections. Patients achieved significant increases in CD4+ T-cell counts without a sustained increase in the level of virus in their blood when compared to patients receiving antiretroviral therapy alone. Chiron's IL-2 is in two international Phase III trials for HIV infection, one of which is sponsored by Chiron and one by the National Institutes of Health. The product is approved under the brand name Proleukin for various cancer indications.

Chiron's (NASDAQ:CHIR) closed Monday at $59.125, up $2.187.

On the HAART front, two new NIH studies suggest it may be feasible for patients whose plasma levels of virus have fallen to undetectable levels to switch from a continuous regimen of highly active antiretroviral therapy to a cyclic course of treatment, with HAART discontinued and resumed in a planned fashion.

"Structured intermittent therapy may prove to be an important treatment option, particularly in settings where continuous HAART is financially untenable," said Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases. He and his team speculate that this strategy could potentially reduce total time on HAART in any given period by as much as 30 percent to 50 percent, thereby reducing HAART-related toxicities and costs, while improving patients' adherence to therapy. They cautioned, however, that further study is needed before intermittent therapy can be recommended to patients who are not participating in closely monitored clinical trials.

In other conference news:

¿ ViroLogic Inc., of South San Francisco, reported that four studies of HIV drug resistance utilized the company's PhenoSense HIV test, a phenotypic test designed to measure resistance or susceptibility of a patient's HIV to antiviral drugs.

¿ Epitope Inc., of Beaverton, Ore, used the conference to introduce the OraQuick HIV-1/2 rapid HIV test to conference attendees. Epitope said the non-invasive oral fluid test for HIV 1 and 2 antibodies provides highly accurate results in about 20 minutes.

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