SAN FRANCISCO -- An experimental drug not available in the United States is luring some American AIDS victims to France, where screen and television star Rock Hudson is battling the deadly disease.
But scientists caution the drug HPA-23 -- which appears to block reproduction of a virus thought to cause acquired immune deficiency syndrome -- is not a cure, has not been fully tested and can have severe, toxic side effects.
U.S. Food and Drug Aministration officials say they have not approved the drug, which bears the chemical name of antimonium tungstate, for experimental use because 'no company has applied for such approval.'
U.S. researchers say they are testing a handful of other experimental drugs -- although on very limited numbers of patients -- and may begin human trials of additional powerful anti-AIDS agents in as little as six months.
'It is hard to give exact numbers because there are many different hospitals in Paris that are using HPA-23 on AIDS patients, but I know American patients are coming to France for treatment,' said Dr. Raymond Dedonder, director of the Institut Pasteur, where scientists first found the AIDS virus in 1983.
'We must be very cautious about saying 'treatment' because at this point it is difficult to be sure the drug will be very effective by the time the full disease has set in.'
Dr. Willy Rozenbaum, a Paris researcher who has worked with HPA-23 for two years, said he has received hundreds of inquiries from Americans stricken with AIDS, which has afflicted nearly 12,000 U.S. victims in the past five years.
'It is very sad because I have to refuse many patients,' he said.
Holly Smith of the San Francisco AIDS Foundation said she knows of 'lots of San Franciscans going to France to get HPA-23,' including several prominent leaders of the city's large homosexual community.
Homosexual and bisexual men comprise three-fourths of those stricken with the immune system disorder that disarms the body's natural disease-fighting capabilities and renders its victims susceptible to cancer and a host of viral and bacterial infections. Nearly 6,000 AIDS patients have died.
Smith believes Hudson's widely publicized trip to Paris to consult AIDS specialists may encourage others to follow.
Scientists urge caution.
'I think it is correct to try HPA-23,' Dedonder said in an interview. 'But you can't think of it as a miracle drug.'
The drug --which also is being tested against cancer -- is considered experimental in France, where 200 AIDS cases are confirmed each year, he said.
In one study of 47 AIDS patients, six showed no signs of the culprit virus after receiving HPA-23 -- but only so long as they were injected with the drug. And, scientists warn, even the absence of the virus does not guarantee a cure.
'We need more systematic testing to explore what HPA-23 can do,' Dedonder said. 'If any patients are lucky and can be cured, we will be very happy, but so far there have been no wonderful results that I know of.'
Dr. Sam Broder, head of the Clinical Oncology Program at the National Cancer Institute in Bethesda, Md., said although HPA-23 'appears to suppress the AIDS virus, I am aware of no published results that show the drug can reverse the underlying immunodeficiency of AIDS or lead to a statistically significant clinical improvement.'
The drug suramin, being tested in the United States, has a similar effect on the virus, he said in an interview.
Both drugs have side effects, he noted. HPA-23 can cause liver problems and damage cells necessary to clot blood. Suramin has been linked to kidney complications.
'Nothing that I've seen presented allows me to conclude that HPA-23 is any more promising than a number of clinical experimental drugs being tried or soon to be tried in this country,' Broder said.
Doctors at the AIDS Clinic at San Francisco General Hospital said since the French studies of HPA-23 lack a control group of people who are not being treated, it is impossible to determine the effectiveness of drug.
'We do not have any hard data from scientists that give us reason to be hopeful about HPA-23,' said Dr. Don Abrams, assistant director of the clinic.
Dr. Lawrence Kaplan, who is conducting the clinic's studies on suramin, said the serious side effects of HPA-23 make extensive testing 'potentially dangerous' to patients already suffering from serious infections.
Broder said scientists at NCI, a world leader in AIDS research, 'now have many potent agents that work at the test-tube level, and I expect two or three of them should be ready for experimental testing in six months.'