WASHINGTON — A new experimental antiviral drug called 3TC, taken in combination with the commonly used drug AZT, decreased AIDS infection and appeared to improve the immune systems of patients better than either drug used alone, according to new studies presented Wednesday.
The findings represented the second piece of encouraging news in AIDS therapy in as many days and further bolstered the opinion of most researchers that combinations of powerful drugs are the best hope for controlling the disease.
Researchers presented data Tuesday showing that another class of drugs, protease inhibitors, produced similar results. The research was released at the Second National Conference (on) Human Retroviruses and Related Infections, a five-day scientific meeting here devoted almost entirely to AIDS.
"The combination of AZT and 3TC is promising," said Dr. John Bartlett of Duke University Medical Center, which conducted one of the studies. "We who treat patients infected with HIV believe that combining different therapeutics offers the potential for more treatment successes."
Researchers studying the 3TC/AZT combination found marked decreases in virus levels in patients' blood and significant increases in CD4 lymphocytes, the essential disease-fighting immune system cells that are the major target of the human immunodeficiency virus.
These results persisted for at least six months, and longer in many patients, researchers said.
But the scientists stressed that it is too soon to know whether the results would translate into prolonged survival or fewer infections. Additional studies are planned to try to answer that question.
"We have not proven that patients will live longer, but we hope that a decrease in the virus will correlate with a decrease in symptoms," said Dr. Joseph Eron, who conducted a study at the University of North Carolina at Chapel Hill School of Medicine.
Other developments at the meeting included a progress report on AIDS vaccine development and a summation of a five-year pilot program of HIV-screening of pregnant women in Los Angeles County, begun by the Department of Health and Human Services in 1989.
Sixty-five percent of the women found infected had no identified risks for HIV infection, a finding that should strengthen the idea of offering the test to all pregnant women, not just those who engage in high-risk behavior, investigators said.
This is especially important in light of recent studies which showed that AZT given to pregnant infected women caused a sharp reduction in transmission of the virus to their babies, they said. Federal health officials are expected to release guidelines on this issue in coming weeks.
In the vaccine arena, researchers reported no new breakthroughs but said that they continue to be optimistic about the prospects that a vaccine will be developed.
"Getting a vaccine for AIDS is possible," said Margaret I. Johnson, acting deputy director of the AIDS division of the National Institute of Allergy and Infectious Diseases. However, she said, "it's going to be very difficult."
She predicted that it would be 1998 or 1999 at the earliest before any candidate vaccines will be ready for trials. "And that would take two to three years," she said, meaning it is unlikely that a vaccine will be widely available until several years after the turn of the century.
Most of the attention Wednesday, however, was on reports about 3TC, also known as lamivudine. The drug, one of a family of drugs known as nucleoside analogs--which also include AZT, DDC and DDI--is made by Glaxo Holdings Inc.
The company said that it intends to seek Food and Drug Administration approval of 3TC before this summer. Currently, the company is providing the drug to about 10,000 AIDS patients worldwide under a special program.