Comment from Joseph O'Donnell

November 12, 2010 Docket No. APHIS-2009-0028 Regulatory Analysis and Development PPD, APHIS, Station 3A-03.8 4700 River Road, Unit 118 Riverdale, MD 20737-1238 Re: Docket No. APHIS-2009-0028 The following comments refer to Docket No. APHIS-2009-0028 IDEXX Laboratories supports the development of a single uniform standard for determining the stability of veterinary biological products. IDEXX offers the following comments for APHIS’ consideration. Definition of “Stability-Indicating Assay” The definition of “stability-indicating assay” in the rule calls for a quantitative assay. The interpretation of most test kits is qualitative in nature – demonstrating the presence or absence of an analyte in significant concentration. These test kits do not report a concentration or titer, so a quantitative result is not needed. For many test kits, a quantitative measurement is used for the qualitative determination (eg, an optical density relative to a cutoff). In some cases, there is only a visual assessment of a reaction. But even when a quantitative measurement is possible, it should not be a required in assessing stability of a qualitative test kit. Number of Test Points in the Study The background states that testing a product at multiple times during its life is appropriate because product potency can “degrade in a non-linear fashion” and that a two-point profile of a degradation curve is “inaccurate and imprecise.” We assume these points are true, but do not understand how they apply to end-life potency of a product. The direction of potency shift over time is always the same and the lowest point is always at the end of the period. It is not clear why the profile of the curve is important in this kind of assessment. Non-linear degradation does not by itself justify multiple time points in the stability study. Testing Date for Establishing Product Expiry The proposed rule at 114.12 calls for setting the expiry date of a serial based on the initiation of the first potency test. This accords with the current rule and established practice. The proposed rule at 114.13 (a) addresses establishing product expiry and calls for testing each serial “beginning on the day of filling into final containers or on the date of final formulation.” The reason for requiring testing on this date is not explained in the background material. It would be impractical to require that the product be tested on the date of filling or final formulation. In the usual course of product development or ongoing production, testing is not tied to such a date. The benefit of linking these events this is not obvious. IDEXX appreciates the opportunity to provide comments and reiterates it support for a uniform standard for determining the stability of veterinary biologics. Sincerely, Joseph W. O’Donnell Regulatory Affairs Manager IDEXX Laboratories, Inc. One IDEXX Drive Westbrook, Maine 04092 207 556-4647 joe-odonnell@idexx.com