February 20, 2007

Immune Response has announced preliminary Phase II study results suggesting that both Remune and IR103, its first- and second-generation HIV vaccine candidates, stabilize CD4+ T-cell counts compared with placebo in HIV patients who have not started antiretroviral therapy. The 36-week data are from a year-long, multicenter safety and immunogenicity study expected to conclude in 2008.

CD4+ T-cells, also known as helper T-cells, are key elements of the immune system and are specifically attacked and killed by the HIV virus. CD4+ count is a critical marker of HIV disease progression that is used in clinical decisionmaking. Unlike currently available drugs that attack the virus, Remune and IR103 are designed to stimulate the body's own immune system to better fight the virus by boosting T-cell activity.

The trial is a randomized, double-blind, safety study being conducted in Italy. The objective of the study is to examine the safety and the ability of Remune and various doses of IR103 to generate HIV-specific immune responses in antiretroviral-naive HIV-infected subjects compared with placebo.

Patients in this interim analysis received either Remune, IR103 in 0.1-, 0.5- and 1- mg doses, or saline every 12 weeks via intramuscular injection. CD4+ cell counts were measured at baseline and at weeks 4, 12, 24 and 36. While the data will not be statistically analyzed until completion of the trial, the data show a trend toward stabilization of CD4+ count in the immunized patients as compared with placebo at weeks 24 and 36.

No substantive difference in effect on CD4+ count was seen between Remune and IR103, and no affect on viral load was detected at this point in the trial as compared with placebo.