A Food and Drug Administration advisory committee agreedWednesday that for proving the efficacy of an AIDS drug,monitoring changes in CD4 white blood cell counts is the nextbest thing to measuring mortality rates.

The FDA's anti-viral drugs advisory committee only reluctantlyformed a consensus about the adequacy of CD4 counts as"surrogate end points" for AIDS drug trials.

But if the FDA adopts this view, the AIDS drug testing processcould be shortened by years. It could also lead to quickermarketing approval of Bristol-Myers Squibb's dideoxyinosine(ddI) and Hoffmann-La Roche's dideoxycytidine (ddC), twopotential AIDS drugs now in Phase I/II clinical trials. Both areavailable through expanded access programs to patients whocannot gain entry into controlled trials.

Initial data suggest that ddI and ddC can slow the decline inCD4 cell counts that characterize AIDS. Using this data, AIDSactivist groups have urged the FDA to approve ddI and ddCbefore the completion of studies that could prove that thedrugs extend life.

The committee rejected the measurement of viral p24 proteinlevels in a patient's blood as an end point for AIDS drug trials.It did suggest that research could point to the use of CD4 countsin combination with other end points, such as blood levels ofbeta-2 microglobulin, a protein produced by activated whiteblood cells.

Concern was expressed that the use of CD4 measurements asthe basis for drug approvals would make efficacy comparisonsamong AIDS drugs more difficult. -- Carol Ezzell021491CD4

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