AIDS Drug Task Force Hears Progress Report on Protease Inhibitors

BETHESDA, Md--Whaijen Soo, MD, vice president for virology, Hoffmann-LaRoche, told the National Task Force on AIDS Drug Development thatthe company's protease inhibitor, saquinavir (Invirase), is nowready for phase III trials.

These randomized double-blind studies will involve 1,000 peoplewith advanced HIV infection who have discontinued or are unableto take AZT (zidovudine, Retrovir) and have CD4 counts of between50 and 300.

Protease inhibitors are antiretroviral agents that block the activityof protease, an enzyme critical to the replication of HIV, EdwardScolnick, MD, executive vice president for science and technology,Merck & Co, said in his overview of this new class of drugs.

Phase I and II Studies

In vitro studies have shown that enzyme inhibition results inproduction of noninfectious virus, he said. Phase I and phaseII studies done in Europe and the United States showed improvementin the number of circulating CD4 lymphocytes and a reduction ofviral load.

The benefit of protease inhibitors may be limited, however, becauseof the ultimate development of drug resistance, a problem commonto all current commercially available antiviral compounds, Dr.Scolnick said.

Invirase, alone and in combination with other antiviral drugs,will be tested against a placebo, with clinical endpoints definedby disease progression and survival, Dr. Soo told the Task Force.He said that phase II studies showed that patients who receivedInvirase in combination with other antiretroviral agents had thegreatest improvement in CD4 cell counts and reduction of viralload.