TIBO DERIVATIVES: MOST SELECTIVE ANTIVIRAL?

Researchers in Belgium and the U. S. have developed a new antiviral which appears to act more selectively against HIV than any other known chemical. Early results were published February 1 in Nature, which is widely considered one of the world's most prestigious scientific journals.

In an important departure from research procedures enforced in the United States, this early report includes not only laboratory results but animal and human safety information as well. After developing a drug (so far only as R82150), researchers gave dogs a thousand times the dose likely to be effective, with no adverse effects. Then six healthy volunteers took a single 200 mg dose orally; blood levels sufficient to inhibit HIV were maintained for over 24 hours, with no toxicity. No test with persons with AIDS or HIV was reported. But the initial human experience could greatly speed future development of the drug, because a huge psychological and legal barrier -- the reluctance to try a new chemical in humans for the first time -- has already been crossed.

In the laboratory, R82150 inhibited HIV in concentrations about 31,000 times less than those toxic to cells; a comparable value for AZT was about 6,200. The drug was effective against five different strains of HIV-1, but was so selective that it did not act against HIV-2, or against any other virus tested. R82150 is believed to inhibit reverse transcriptase, like AZT; but unlike AZT, it is not a nucleoside analog. R82150 is difficult to manufacture in quanWåby currently known techniques.

R82150 was developed in Belgium, at the Katholicke Universiteit in Leuven, and the Janssen Research Foundation in Beerse. The drug-development strategy was to start with 600 basic molecules, and then use intelligent trial and error to synthesize related chemicals to find ones which are more effective in laboratory assays. 'TIBO' is an abbreviation for the name of one of the chemicals.

Until the drug is tested on persons with AIDS or HIV, it is not possible to know whether it will be effective. We do not know what clinical trials are planned.