U.S. Company Virxsys Says Using AIDS to Fight AIDS

Early results presented to the 17th Conference on Retroviruses and Opportunistic Infections in San Francisco suggest a gene therapy approach to controlling HIV could be effective. Maryland-based Virxsys Corp. said two products in development have shown promise.

A gene therapy treatment called VRX496 takes a patient's CD4 T-cells, the cells that HIV infects, and treats them with an RNA antisense product. RNA is the genetic material retroviruses such as HIV use, and antisense approaches involve a type of mirror image of the genetic sequence to block genetic activity. A crippled HIV virus genetically engineered with the antisense sequence then is used to infect the T-cells.

"VRX496 lies inactive in a patient's white blood cells (specifically the CD4 cells), waiting for HIV to enter that cell," said Virxsys. "When HIV does enter, replication of HIV within that cell activates VRX496, which then binds to and destroys the HIV."

A team at the University of Pennsylvania School of Medicine is conducting a Phase I/II trial of 65 HIV-infected volunteers who are currently taking breaks in their AIDS drug regimens. While on the breaks, participants are treated with VRX496. At least one patient is showing a strong effect, said Garry McGarrity, head of science at Virxsys.

In another study, Virxsys said its genetically engineered vaccine VRX1023 was given to 15 monkeys at three different doses. Though it did not prevent infection, it did reduce viral load. The vaccine is made using a crippled HIV strain. The company is now seeking permission to conduct human trials.

"I think the vaccine is more the interesting one because it is far more doable in the end," said Dr. Joep Lange, head of the Amsterdam Institute for Global Health and Development and a member of Virxsys' medical advisory board. "It doesn't prevent infection, but it does give good reduction in viral load," said Lange, also a former president of the International AIDS Society.

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