Scientists at Bio-Technology General Corp. said Thursday theyhave discovered an action of the HIV reverse transcriptaseenzyme that appears to be unique to the virus, creating a muchbetter target for therapeutic intervention.

The company's stock (NASDAQ:BTGC) jumped $1.50 to $9.50Thursday on the news.

Existing inhibitors of reverse transcriptase -- AZT, ddI and ddC-- all have dangerous side effects because they can also affectnormal enzyme activities. By contrast, the activity of reversetranscriptase described by BTGC investigators might be blockedwithout adverse consequences.

Purified HIV reverse transcriptase cleaves the virus' RNA whenit is attached to its transcription primer, a step at the beginningof the viral replication process. This enzymatic action, calledRNaseD activity, is only found with HIV. Reverse transcriptasesfrom other sources do not perform this step, the researchersreported at a National Institutes of Health-sponsoredconference in San Diego.

The discovery was made "incidentally" during research on HIVgenes funded by a contract from the NIH, said companyspokeswoman Leah Berkovits.

"If it works, it is very important," Berkovits told BioWorld.

The New York company is screening for compounds that wouldinterfere with this specific action of the enzyme. -- RobertaFriedman, Ph.D.

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