Completed Phase I studies indicate that MicroGeneSys Inc.'sAIDS vaccine is safe and that it boosts both the antibody andcellular immune responses in HIV-positive individuals.

The vaccine, a genetically engineered HIV gp160 precursorenvelope protein, also stabilized the T cell count in patientsshowing a positive immune response. T cells are the targets ofHIV, the AIDS virus.

"These results are very exciting. They reinforce our earlyoptimism that we could increase the immune response beyondthat induced by HIV upon infection," MicroGeneSys PresidentFranklin Volvovitz told BioWorld.

Volvovitz cautioned that the study must be validated by acontrolled Phase II clinical efficacy trial. The Department ofDefense began such a double-blind, placebo-controlled study ofthe vaccine, called SAI-5, or VaxSyn HIV-1, in November.Several hundred HIV-positive individuals will be tested, saidVolvovitz.

Dr. Robert R. Redfield of the Walter Reed Army Institute ofResearch and his colleagues report the results of the 10-monthSAI-5 Phase I study in today's New England Journal ofMedicine. Fifteen asymptomatic HIV-1 positive individualswere given three doses of SAI-5 over four months. Anadditional 15 asymptomatic HIV-1 positive individualsreceived six doses over six months.

Thirteen patients receiving the higher dose and six patientsreceiving the lower dose mounted an immune response againstHIV that exceeded that provoked by the infection alone. Notonly did SAI-5 stimulate the production of new antibodies, butit also induced T cells to mount a cellular immune responseagainst HIV.

After 10 months, the 19 responders showed only a two-tenthsof 1 percent loss of T cells. The T cell count in the otherindividuals decreased 7.3 percent.

The results suggest that immunotherapy may be useful indelaying the onset of AIDS symptoms, said Volvovitz. ThePhase I patients are now part of an extended study.

Other clinical studies under way by the privately held Meriden,Conn.-based MicroGeneSys include SAI-5 to protect individualsfrom infection, HIV core protein p24 to protect individualsfrom infection, and a combination therapy of SAI-5 and Foodand Drug Administration-approved AZT. AZT inhibits HIVreplication.

Other AIDS vaccine-based immunotherapies in U.S. clinicaltrials include Genentech Inc.'s gp120 HIV envelope protein, inPhase I studies since November, and Immune Response Corp.'skilled HIV virus, in Phase II/III studies since September.

-- Carol Talkington Verser, Ph.D. Special to BioWorld

(c) 1997 American Health Consultants. All rights reserved.