Immune Response Corp. on Thursday said it has developed anassay of HIV infection that supports the company's desire touse viral burden as a surrogate end point in trials of its AIDSvaccine.

Reporting in the current AIDS Research and HumanRetroviruses, the San Diego company said it has developed apolymerase chain reaction assay that measures the amount ofHIV DNA in a patient's blood cells. Use of the assay has shown acorrelation between the viral burden in HIV-infected peopleand the clinical stage of infection, the company said.

The assay correlated with a standard virus isolation assay.Moreover, higher levels of virus in the blood correlated withmore-advanced stages of HIV infection. Less viral burdencorrelated with the asymptomatic phase of disease.

The company (NASDAQ:IMNR) is using viral burden as asurrogate marker in Phase II/III trials of its therapeuticvaccine. The testing, sponsored by Immune Response andRhone-Poulenc Rorer Inc., is evaluating the efficacy of thevaccine based on several markers of disease progress. Thevaccine consists of whole, killed virus that is missing its gp120coat protein.

Last November, an FDA advisory committee recommendedagainst use of CD4 cell counts as a primary end point in trials ofAIDS vaccines. Conventional clinical end points include onset ofopportunistic infections and patient mortality. Nevertheless,said Immune Response spokesman Steven Basta, FDA policy isto promote use of surrogate markers to speed approvals of newdrugs.

To hedge its bets, the company plans a larger trial using clinicalend points, but would submit successful results using surrogatemarkers in 1993 while the larger study is in progress, saidBasta.

The correlative data was obtained in an investigation separatefrom the Phase II/III trials of the vaccine, Basta said.

The stock gained 25 cents to $28.50.

-- Roberta Friedman, Ph.D. Special to BioWorld

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