Testing, testing: CD4.

Testing, testing: CD4

CD4, a drug designed to prevent the spread of the AIDS virus to new cells, entered preliminary safety trials in humans last week at the National Cancer Institute in Bethesda, Md. Two more medical centers also will test the drug. A total of about 50 patients with advanced AIDS will receive the treatment.

A genetically engineered protein, CD4 is named for a naturally occurring protein found on the surface of T4 helper cells, immune system cells that are particularly vulnerable to the virus (SN: 6/25/88, p.405; 1/16/88, p.40). The virus infects by attaching to CD4 protein to gain entry to the cell. The drug CD4 functions as a decoy, binding the virus before it can attach to infect cells, multiply and destroy the cells. It is the first AIDS treatment to be tested in humans that was designed based on the structure of the virus. Theoretically, it might be used to prevent infection immediately after exposure to the virus.

Large-scale testing will begin if all goes well during the preliminary safety trials, which are expected to take about six months. CD4 is not expected to be the last word in AIDS treatment, and other work suggests it may be more effective in combination with other treatments, such as zidovudine (AZT), which interrupts viral replication inside the cell.