New AIDS Drug Called Far Less Toxic Than AZT
Researchers Tuesday reported preliminary data showing that an experimental drug against AIDS may be just as effective as AZT but far less toxic.
AZT is the only drug now known to prolong the lives of some AIDS patients, but its severe side effects, including debilitating anemia and bone marrow suppression, often require physicians to reduce the dosage levels or suspend use of the drug altogether.
The new experimental drug, DDC, has caused only skin rashes and the temporary loss of platelets, which are cells that help the clotting of blood, Dr. Samuel E. Broder of the National Cancer Institute told the Third International Conference on AIDS here.
In addition, the drug has produced a rise in disease-fighting T-4 cells without causing bone marrow suppression or weight loss. “Some patients did show immunologic improvement,” he said.
Broder emphasized, however, that the DDC trials are in the earliest of stages of testing and that his observations are based on only 20 patients.
But Broder also raised the possibility that AZT and DDC, used together, might be more effective than either one alone. Such a clinical trial, he said, would “make sense.”
“Something can be done about the AIDS virus, even in advanced disease,” said Broder, who is director of clinical oncology at the cancer institute. “It is true that we do not have a cure in hand, but it would be erroneous to conclude that nothing can be done or that we are not well on the way to making extremely important progress against this extremely serious threat to American public health.”
He added, “I don’t see how anyone can conclude that something can’t be done about AIDS at some level.”
In an interview, Broder said that one potential problem with DDC, or dideoxycytadine, is that it does not appear very efficient in getting across the so-called blood-brain barrier. This barrier is a natural defense mechanism that keeps certain drugs and other chemicals circulating in the body from reaching the brain.
More Powerful
According to Broder, DDC is only one-fifth or one-sixth as effective as AZT in penetrating the blood-brain barrier. On the other hand, he noted, DDC is 10 to 20 times more powerful a drug than AZT--so that “a small amount getting across the brain may be a lot.”
At this point, Broder said, “it is impossible to know which trade-off is the critical one.”
AZT, or azidothymidine, was licensed as an AIDS drug in March. It was first given to AIDS patients in July, 1985. By September, 1986, during the test’s second phase, the trial was halted and the drug made widely available after it was shown to have dramatically prolonged the lives of some AIDS patients while reducing both the severity and frequency of infections.
AZT now is available by prescription, although it is still in short supply and costs a patient up to $10,000 a year.
New Human Trial
Broder also said a new AZT trial is set to begin in July on patients who are infected with the virus but who are still well. At present, only people who have come down with AIDS are receiving the drug.
Also on Tuesday, USC virologist Suraiya Rasheed announced the development of a new technique that determines the amount of AIDS virus circulating in one’s bloodstream and possibly how quickly an infected person is coming down with the disease.
The new test may also help doctors determine how effectively a patient is responding to drug treatments, Rasheed said.
“With this method, we can tell how many cells in the body are infected, what type of cells are infected, what level of the virus is present in cells, and which of several components of the virus a drug may be attacking,” she added.
Can Identify Cells
Rasheed, director of USC’s Laboratory of Viral Oncology and AIDS Research, now is conducting studies to correlate the amount of AIDS virus present with a patient’s symptoms.
The new test, called “in situ hybridization,” allows scientists to identify AIDS-infected cells directly as they occur in the blood rather than amplifying viral particles by growing them in culture.
The test differs from antibody tests for the AIDS virus in that the antibody test determines only if a patient has been exposed to the virus and not how widespread the virus is in the patient’s system.
First Test on Humans
In a late night presentation, Dr. Daniel Zagury reported preliminary results of the world’s first test on humans of an experimental vaccine against AIDS. Last July, the French scientist injected himself and 11 other volunteers in Zaire with a vaccine composed of a man-made virus containing a piece of the AIDS virus.
Zagury said it is too early to tell whether the vaccine will protect against infection by the AIDS virus, but that the vaccine did produce the desired result of causing the volunteers’ immune systems to make antibodies against the AIDS virus.
At a news conference following the presentation, Dr. Dani Bolognesi of Duke University, an expert on experimental AIDS vaccines, praised Zagury’s results and said the Frenchman’s work will be repeated in similar experiments on humans in this country by early 1988.
Also on the topic of vaccines, Dr. W. F. H. Jarrett of the University of Glasgow, Scotland, announced that he has developed an experimental vaccine consisting of an artificial AIDS virus that is incapable of causing the disease. This candidate vaccine may join several others in preliminary human trials in the next year.
Earlier in the day, Dr. James Curran, chief of the AIDS program at the U.S. Centers for Disease Control, estimated that one in every 30 American males between the ages of 20 and 50 is now infected by the AIDS virus. And by 1991, he said, such cases will have caused enough deaths to make AIDS the second leading cause of premature death among men of all ages, after accidents.
The U.S. Public Health Service has estimated that 270,000 cases of AIDS, with 179,000 deaths, will have occurred in the United States by 1991.
