T Cell Sciences Inc. of Cambridge, Mass., announced Wednesdaythat its subsidiary, T Cell Diagnostics Inc., has filed for FDAapproval to market its TRAx CD4 test kit.
The kit is used to count serum levels of CD4 cells, whichprovide a measure of a patient's immune status. MonitoringCD4 levels has become routine in managing patients with HIVinfection, for instance, but can also be used for other infectiousdiseases, cancer and immune-related disorders.
"The clinical use of cell enumeration has increased rapidly asthe connection between CD4 levels and the progression of HIVhas become more apparent," said William Gelb, chief executiveofficer of T Cell Diagnostics.
The National Institute of Allergies and Infectious Diseases(NIAID) has issued clinical guidelines recommending that HIV-infected patients undergo two to four CD4 tests per year untilthe disease reaches its final stages. A healthy individual has800 to 1,000 CD4 cells per microliter, Gelb explained. But whenCD4 levels in HIV-infected individuals drop to 500 cells permicroliter, physicians know to start AZT therapy. They switchto pentamidine drug therapy (for Pneumocystis pneumonia)when the levels drop to 200 cells per microliter, Gelbexplained.
In fact, the Centers for Disease Control (CDC) in Atlanta haveproposed that these "diagnostic windows" be used to defineAIDS, Gelb told BioWorld. The CDC recommended discontinuingall therapy below 200 cells per microliter because it serves nopurpose, Gelb added.
The current method for enumerating CD4 cells is flowcytometry, which depends on living cells. T Cell Diagnostics'assay, on the other hand, solubilizes the cells' receptors andanalyzes them by a microtiter colorimetric immunoassay. Gelbsaid that results obtained by the two different techniquescorrelate by 90 percent, but the immunoassay "is faster, easier,and more cost-efficient (than flow cytometry)"
T Cell Sciences stock was up 75 cents on Wednesday to $6.75.-- Jennifer Van Brunt
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