Report Revives Interest in Experimental AIDS Drug : Treatment: The FDA remains skeptical of isoprinosine, despite impending publication of a favorable Scandinavian study in a prestigious journal.

Interest in an all but forgotten experimental AIDS drug, isoprinosine, has been renewed by the New England Journal of Medicine’s decision to publish a favorable Scandinavian study of the medication.

“Treatment with isoprinosine appears to delay progression to AIDS” in infected individuals, Dr. Court Pedersen of the University of Copenhagen said Tuesday at a medical meeting held in conjunction with the Sixth International Conference on AIDS.

But officials of the U.S. Food and Drug Administration are skeptical of the findings. In an editorial that will be published in the New England Journal on Thursday along with the study, FDA officials said “a confirmatory study (was) mandatory before claims of efficacy can be accepted.”

Before the completion of the Scandinavian study, there was so little data supporting isoprinosine’s effectiveness against AIDS that the drug’s manufacturer, Newport Pharmaceuticals International Inc. of Laguna Hills, had planned to abandon its testing program. Other studies conducted in the United States and Britain have shown no benefit.

Isoprinosine is believed to boost the function of immune system cells and help them ward off the ravages of the AIDS virus. It does not appear to act directly against the human immunodeficiency virus, which causes AIDS.

The 831-person study was conducted in Denmark and Sweden between 1986 and 1988. The participants were mostly HIV-infected white gay men who had yet to become ill.

The study showed that patients who took three isoprinosine tablets a day for 24 weeks developed AIDS at a significantly lower rate than patients randomly assigned to take placebo tablets, said Pedersen, who directed the research.

Of the approximately 400 patients in each group, AIDS, the most advanced stage of HIV infection, developed in two in the isoprinosine group as compared to 17 in the placebo group. No serious side effects were observed.

Pederson said Tuesday that these beneficial effects appear to persist for up to 48 weeks.

But other results were less convincing. For example, no significant differences were found in progression to many pre-AIDS conditions, such as weight loss and diarrhea.

Pedersen also acknowledged that the drug failed to restore immune function and the amount of AIDS virus in the blood stream did not change. In fact, in both groups of patients the concentration of T-4 white blood cells, which are destroyed by the AIDS virus, decreased significantly.

As news of the journal publication was made public Tuesday, the company’s stock jumped from 81.25 cents to $3.625 per share.

Judith Archbold, a Newport vice president, said the company “can’t really undertake additional studies until we can get support and endorsement from the AIDS research community. We are hopeful that the publication will be helpful in getting that support.”

Said Pedersen: “If there are no new studies, I don’t think isoprinosine treatment has any future.”

Because of the success of AZT and medications to prevent AIDS-related pneumonia, a very large study of isoprinosine would be necessary “to show an effect,” said Dr. Thomas C. Merigan of Stanford University, a key member of the federally sponsored AIDS Clinical Trial Group. “Until we understand a little more about (isoprinosine’s) mechanism of action, it is hard to make a (large-scale) commitment because we have so many competing priorities.”

Isoprinosine is marketed by Newport and its licensees in dozens of countries, including Canada, Mexico, Japan and New Zealand, for herpes and other viral infections. The FDA, unconvinced of its effectiveness, has rejected Newport’s numerous requests for marketing approval in the United States.

Publication of the study also underscores the importance of leading medical journals in influencing medical research priorities.

When similar results from the Scandinavian study were announced at the international AIDS conference in Montreal last June, they attracted relatively little attention from scientists, AIDS activists and the news media.