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Executive Summary

ZENITH's TOLAZAMIDE RAT STUDIES ARE NOT "CLINICAL" and therefore do not meet the requirements for marketing exclusivity under the ANDA/patent law, FDA Center for Drugs and Biologics Director Harry Meyer, MD, told the firm in a recent letter. Meyer stated that Zenith's petition for three years of tolazamide exclusivity does not meet the statutory exclusivity requirement that an ANDA for a drug product that has been previously approved "contain 'reports of new clinical investigations (other than bioavailability studies) essential to the approval of the application and conducted or sponsored by the applicant.' " In March, Zenith petitioned FDA for three-years marketing exclusivity for its version of tolazamide (Upjohn's Tolinase) on the basis that the rat studies it conducted prior to the Oct. 3 approval met the statutory exclusivity requirements of "clinical" and "essential." Zenith asserted that the legislative intent was not to limit "clinical" to human studies and that the rat studies were "essential" because they were required by FDA ("The Pink Sheet" March 18, p. 4). Meyer told Zenith that it was not entitled to exclusivity because "your application did not contain clinical investigations." Clinical investigations, he explained, "are, by common usage and legislative intent, those investigations that study human subjects or patients. Your application contained only animal studies:" Zenith's petition also requested that "all NDA's for tolazamide be required to include studies similar and equivalent to those conducted by Zenith for purposes of compliance with current FDA guideline labeling for tolazamide drug products." Responding to that request, Meyer stated that "because the agency is denying your request for exclusivity, we do not anticipate receiving any NDA's for tolazamide." ANDAs, under the provisions of the FD&C Act, "are not required to contain studies such as those done by Zenith, because the tolazamide tablets are listed drugs within the meaning of Section 505(j) (6)," Meyer said.

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