Drug duo uses synergy to fight AIDS virus.

Drugs duo uses synergy to fight AIDS virus

A pigment derived from red blood cells slows replication of the AIDS virus in cell cultures, especially when used in combination with the drug zidovudine, researchers report in the March 1 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES.

Zidovudine, currently the only compound approved by the FDA for clinical use against the AIDS virus (HIV), does not fight off the disease indefinitely, in part because the virus tends to develop resistance to it after six months or more of treatment, notes study coauthor Nader G. Abraham, a molecular hematologist at New York Medical College in Valhalla. The new findings may offer a way to overcome this drug resistance, he and his colleagues suggest.

The iron-rich pigment, called heme, helps hemoglobin carry oxygen through the body. A previous study by Abraham's group indicated that heme might help stave off the anemia brought on by zidovudine treatment, Abraham says.

In the new study, he and his co-workers used laboratory cultures of HIV-infected human T-lymphocytes. They found that heme alone slowed the replication of a zidovudine-sensitive strain of HIV and, when combined with zidovudine, slightly improved that drug's ability to slow viral growth. In a zidovudine-resistant strain, neither drug alone slowed viral replication. But when the researchers applied the two drugs together, the combo nearly halted replication of the otherwise resistant strain.

This "surprising" synergy, says Abraham, suggests that physicians could prescribe lower doses of zidovudine to limit its toxic side effects on bone marrow cells, while also using heme to help slow the disease's progression. Although the FDA has not yet approved heme for the treatment of AIDS, U.S. physicians do use it to treat several metabolic disorders, leaving open the possibility of prescribing the drug for some patients with AIDS. "AIDS patients now can start taking heme at a small dose," Abraham asserts.

Howard Z. Streicher of the National Cancer Institute in Bethesda, Md., notes that "myriad other drugs" have slowed HIV growth in cell cultures. Scientists still must prove that heme fights HIV in people and determine the best dosages for treatment, he says.

Nevertheless, the new study shows promise, Streicher adds. He's especially intrigued by the finding that the two drugs somehow conspire to stop the proliferation of a zidovudine-resistant HIV strain.