The National Institute of Allergy and Infectious Diseases(NIAID) announced Friday that it has begun a trial to comparein HIV-infected people combinations of zidovudine (AZT),zalcitabine (ddC) and Ro 31-8959, an experimental drug thatinhibits an enzyme HIV needs to reproduce.

The Phase II trial is the first U.S. study to examine Ro 31-8959.Made by Hoffmann-La Roche Inc., Ro 31-8959 was previouslystudied in Phase I and II trials in Europe, where no significantside effects were seen when the drug was given alone or incombination with AZT.

In the NIAID trial, investigators at 10 sites of the AIDS ClinicalTrial Group network will evaluate the combination therapiesfor safety, tolerance and immune system response.

"This trial will further extend our knowledge of Ro 31-8959 asan HIV therapy," said Anthony Fauci, director of NIAID. "Usingthis drug to target and interfere with a particular aspect ofHIV's life cycle may lead to a more effective and safer therapyfor HIV disease."

Ro 31-8959 interferes with the activity of the protease enzymethat HIV uses to separate large proteins into smaller parts thatare needed to make new copies of virus. If the proteins are notcleaved by protease, new virus is still assembled, but it cannotfunction properly or cause infection.

During the 24-week study, 300 participants will be assigned atrandom to take one of three combinations: Ro 31-8959 andAZT; AZT and ddC; or Ro 31-8959, AZT and ddC. Of the threedrugs, only AZT is approved by FDA as a single therapy for HIVinfection. FDA has approved ddC, but only for use incombination with AZT.

Investigators will measure CD4+ T cell responses and theamount of virus present in each participant's peripheral blood.

The trial is chaired by physicians Ann Collier and LawrenceCorey of the University of Washington in Seattle. -- NancyGarcia

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