Last-Ditch Weapon Against HIV

A medicine that blocks the AIDS virus from getting inside cells has shown promise as a last-ditch treatment for patients who fail to respond to standard AIDS drugs.

The medicine, code-named T-20, is still in early-stage testing, but researchers said Monday that it could offer a reprieve for those who have run out of options. T-20 was discovered at Duke University. It is being developed by Hoffmann-La Roche Inc. and Trimeris Inc., a small biotech company in Durham, N.C.

The drug is the furthest along of a new class of AIDS medicines called fusion inhibitors. They work by thwarting the virus's ability to fuse with blood cells and insert their genetic material into them.

"It looks quite good," said Dr. Michael Saag of the University of Alabama. "We are looking at something with a totally different method of action. It is an important, potent new option."

However, the treatment has one large drawback compared with other AIDS drugs: Instead of being a pill, it must be injected twice daily. Nevertheless, Saag said patients in advanced stages of AIDS are willing to give themselves shots, and they seem to tolerate the drug well.

The results were reported Monday by Dr. Jay Lalezari of Quest Clinical Research in San Francisco at a meeting of the American Society for Microbiology.

Other AIDS drugs work principally by thwarting the virus's ability to stitch its genetic material into cells it has invaded or by blocking its ability to disperse mature copies of itself.

Doctors gave T-20 to 55 people who had high levels of the AIDS virus despite trying many different combinations of AIDS medicines. While these standard drugs have proved to be life savers for many with AIDS, they do not work for all patients.

Doctors administered T-20 in combination with other drugs, even though the patients' HIV was resistant to the older medicines. After four months of treatment, virus levels fell significantly in 33 of the volunteers. In 20 of them, the virus fell to levels too low to be measured.

Saag cautioned that the treatment is unlikely to work forever. But he said doctors hope it will delay rebound of the virus for perhaps a year.

T-20 is part of the protein that makes up the AIDS virus' outer coat. Ordinarily it comes into play with another peptide -- T-21 -- as the AIDS virus grabs onto blood cells and prepares to enter them. Scientists found that flooding the body with extra copies of T-20 gums up this attachment process.

Written By Daniel Q. Haney