It could be an ideal drug to fight HIV—a drug that does exactly what doctors want it to do with minimal side effects.
“We know that it works in vitro,” says genetics professor Leonore Herzenberg. “But we don’t know how HIV patients will react.”
The drug, Gd-Tex, was developed by Sunnyvale-based Pharmacyclics and is currently being tested in humans as a treatment for cancers of the lung, brain, breast and pancreas. Gd-Tex targets tumor cells, disrupting the mechanisms that protect them from a type of stress. The cells then die more readily during radiation treatment.
Because HIV-infected cells are similarly weakened, Herzenberg and her partner in life and lab, emeritus professor of genetics Leonard Herzenberg, had a “hunch” that Gd-Tex might kill those cells, too. To test that hypothesis, the couple turned to Omar Perez, a first-year graduate student who was rotating through their lab.
Perez treated HIV-infected blood samples with Gd-Tex for two years, encouraged by his adviser, associate professor Garry Nolan, PhD ’89, who also had been a student in the Herzenbergs’ lab. Perez discovered that a key type of T cell that coordinates the body’s immune response—and is devastated by HIV—was committing a kind of “cell suicide” in reaction to the drug. In February, the researchers published an article in the Proceedings of the National Academy of Science stating that Gd-Tex “could prove quite useful for removing HIV-producing cells.”
The Herzenbergs, who have been researching HIV since 1989, are cautiously optimistic about Gd-Tex. In the lab, low doses of Gd-Tex kill HIV-infected T cells, leaving healthy white blood cells untouched. Although current drugs for HIV stop the virus from replicating, they don’t kill the infected cells. With Gd-Tex, the Herzenbergs say, it is conceivable that those cells could be eliminated.
But the researchers won’t know how effective Gd-Tex is, or whether its rapid destruction of HIV-infected T cells will release harmful toxins into the body, until it can be tested in patients. Those clinical trials could start as early as June at Stanford’s Positive Care Clinic.
Will Gd-Tex be a dream drug? Leonard Herzenberg uses a bridge player’s analogy to describe his view: “I feel encouraged, but I also have lived long enough to know that there are a lot of steps between bidding and making a slam.”
