Turning DNA into a therapeutic treatment usually means delivering the genetic material directly into cells where it can act as native DNA does, coding for needed proteins. Now researchers are using DNA in a new class of drugs that rev up the immune system, potentially helping to boost vaccines' power and even to fight cancer-all without ever entering a cell.

The new drugs consist of short synthetic DNA segments that mimic gene sequences found only in bacteria. The segments bind to receptors on the surface of immune cells; the cells interpret the molecules as signs of a bacterial infection and respond by ramping up the body's defenses. The first use of the technology in humans is likely to be with vaccines, in order to boost the immune system's response to inoculation, says Ethan Shevach, an immunologist at the National Institute of Allergy and Infectious Diseases. In tests on animals, the DNA segments are "unbelievably good," Shevach says.

Dynavax in Emeryville, CA, has completed early human-safety trials of an immune-stimulating DNA sequence, which when combined with a standard hepatitis B vaccine, seems to help the vaccine take effect faster and with fewer injections. Because slightly different DNA sequences may preferentially trigger specific elements of the immune system, the drugs can be tailored for particular uses such as activating natural killer cells, which attack cancerous cells. Shevach believes that the DNA fragment technology "will have a greater use [with] vaccines than as a stand-alone drug," but even that would be greatly welcomed by researchers.

A SLICE OF THE SYNTHETIC DNA MARKET
COMPANY	TARGET	STAGE
Coley Pharmaceutical (Wellesley, MA)	Alergies, asthma, hepatitis B	Human trials
Dynavax (Emeryville, CA)	Allergies, cancer, hepatitis B	Human trials
Hybridon (Cambridge, MA)	Cancer	Animal Research