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STANDARDIZED EXTRACTS BASED ON BIOEQUIVALENT UNITS ENDORSED BY ALLERGENICS ADVISORY CMTE.; CAT EXTRACT STANDARDIZATION MAY BE REQUIRED BY JANUARY 1992

Executive Summary

FDA's effort to standardize allergenic extracts by developing bioequivalent units based on potency was unanimously endorsed by the agency's Allergenic Products Advisory Committee at its Feb. 4 meeting. After the committee heard progress reports from FDA on standardizing mite, cat, and grass extracts, committee Chairman Robert Reisman, MD, pledged the panel's support for the agency's effort. "This is a major step forward, [and is] much needed in terms of allergenic extracts," Reisman declared. FDA has been working on developing standards for allergenic extracts for more than a decade. Representatives from FDA's Allergenic Products Lab, including Acting Director Paul Turkeltaub, MD, explained how the lab has developed standard allergy units to measure extract potency. These units are based on measurements of skin irritation among allergenic individuals and can be correlated to in vitro qualitative and quantitative evaluations of extracts. Committee member Charles Reed, MD, Mayo Clinic, suggested that "the concept of the allergy unit" offers "enormous intuitive appeal" because it "standardizes not only the particular material, [but] also gives us a frame of reference where we can compare ragweed to mite to cate to something else." Meeting for the first time since May 1988, the committee was asked by FDA to comment on two issues arising from the conversion to standardized units. First, some standardized extracts, like cat and Bermuda grass, are currently labeled at 100,000 "arbitrary" units, but would have to be relabeled at 10,000 to reflect their true potency. Second, currently marketed nonstandardized extracts employ a variety of potency measurements, and physicians will have to be educated about the new units when standardization is required. The first issue, Turkeltaub said, is a safety issue: physicians reading the new label for Bermuda grass and cat extracts may be tempted to give 10 times the dose. However, he added, "very few" people currently use standardized Bermuda grass extract, and "of the total cat extract sold, 95%-plus is unstandardized," so FDA will only have to inform a few physicians of the change. Reisman suggested that FDA notify those physicians "personally by telephone and letter. It's just too critical an issue to do otherwise." The committee reiterated the position it took three years ago that clinical data is not necessary to support standardized grass extract licensing applications ("The Pink Sheet" May 30, 1988, T&G-4). The committee also asked that FDA collect more regional data on Bermuda grass before making the proposed labeling change. The second issue, replacing nonstandardized products with standardized, "is the kind of generic issue that's going to impact the whole profession as we go," Turkeltaub said. FDA has already asked industry to halt marketing of nonstandard mite extract, and hopes to do the same for cat extract by January 1992. Committee member John Ohman, MD, New England Medical Center, predicted that the removal of nonstandard extracts from the market would be difficult because "there's absolutely no comprehension of what these allergy units are" among the physician population. Another problem, Turkeltaub said, is that past experience with nonstandard extracts will be a poor guide for physicians using the new products because "we don't know the potency of the unstandardized cat extract that's out there." FDA, therefore, will ask physicians using the standardized products for the first time to proceed with each patient as if they were just starting treatment and begin at a low initial dose, Turkeltaub said. FDA originally planned to require all cat extracts to be standardized by October 1990, the same time as the requirement for standardizing mites. That deadline was later moved back to January 1992. However, FDA has found that the many different types of cat extract are compositionally like one of two or three models: hair, pelt, and possibly "modified pelt." As a result, FDA "may have to extend" the January 1992 deadline, Turkeltaub said.
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