By Randall Osborne

VaxGen Inc. said a clinic in Philadelphia began inoculating volunteers in the first-ever North American trial of the company's HIV vaccine.

The trial, expected to enroll 5,000 volunteers at high risk for infection, will include 30 to 40 other sites in Baltimore, Chicago, Denver, Los Angeles and St. Louis.

"It'll be a three-year study," said Dan Reiner, chief operating officer of South San Francisco-based VaxGen. Participants primarily will be gay males and individuals with HIV-positive partners.

"We're giving them a lot of counseling to be safe in their sexual practices," Reiner told BioWorld Today. Since participants have no idea whether they're getting the vaccine or placebo, they are expected to comply behaviorally.

"You're not going to see a differential in protection," Reiner said. "The protection that will be intrinsic to the group will be identical, whether they receive the placebo or the vaccine."

Statistics have established how many subjects will get HIV even when they say they are practicing safe sexual habits. No HIV-positive subjects will be accepted.

"The tests are very good now," Reiner said. "If you become HIV infected, the test will readily show that in a quick period of time."

VaxGen gained the FDA's go-ahead for the trial in June. This fall, the company — spun off from Genentech Inc., also of South San Francisco — will begin a Phase III trial in Thailand. (See BioWorld Today, June 4, 1998, p. 1.)

The vaccine, called AIDSVAX, uses recombinant versions of a protein called glycoprotein 120 (gp120) from two different strains of HIV. Gp120 is a major envelope protein from HIV that smuggles the virus into immune cells.

AIDSVAX is intended to produce antibodies to stymie HIV's ability to infect immune cells. The American formulation will contain versions of gp120 from the predominant strains of HIV found in North America, Western Europe and Australia. The Thai vaccine will come from strains predominant in South Asia.

In June 1994, the National Institutes of Health (NIH) decided to shelve plans to fund a Phase III trial of gp120 vaccines after funding Phase I and Phase II studies of vaccines developed by Genentech and Chiron Corp., of Emeryville, Calif. In February 1996, Genentech formed VaxGen to take control of the gp120 project and see the endeavor through Phase III trials.

Unlike the vaccines tested by NIH, VaxGen's product is a bivalent version of gp120. *