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Claims to Sustained-Release Formulation of Bupropion Improperly Limited to Specific Examples in Specification

September 22, 2003

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Last Month at the Federal Circuit - October 2003

Judges: Newman (author), Mayer and Bryson

In Glaxo Wellcome, Inc. v. Andrx Pharmaceuticals, Inc., No. 02-1348 (Fed. Cir. Sept. 22, 2003), the Federal Circuit rejected the district court’s claim construction and reversed a SJ of noninfringement.

Glaxo Wellcome, Inc. (“Glaxo”) is the assignee of U.S. Patent No. 5,427,798 (“the ’798 patent”), a patent covering a sustained-release formulation of bupropion, the active ingredient in the antidepressant medicine Wellbutrin® SR and the smokingcessation medicine having the brand name Zyban®. Claim 1 of the ’798 patent describes a controlled sustained-release tablet comprising 25 to 500 mg of bupropion hydrochloride and hydroxypropyl methylcellulose (“HPMC”) having a ratio from 0.19:1 to 1.1:1 of HPMC to bupropion hydrochloride, where the tablet has a specific release rate.

Andrx Pharmaceuticals, Inc. (“Andrx”) filed an ANDA and sought FDA approval for sustainedrelease products with the same identity of active ingredient and properties of Wellbutrin® SR and Zyban®. Andrx certified to the FDA that the Andrx products do not infringe the Glaxo ’798 patent or that the patent is invalid.

Glaxo then sued Andrx in the District Court for the Southern District of Florida, claiming that Andrx’s proposed sustained-release tablets infringe the ’798 patent. The district court granted SJ of noninfringement because Andrx uses a lower molecular weight and lower viscosity HPMC than the grade of HPMC used in the examples of the ’798 patent. Andrx asserted that it controls the release of bupropion in ways other than through the use of HPMC.

The Federal Circuit disagreed, concluding that the district court’s claim construction was unduly restrictive. The claims were originally drawn to all excipients retarding the release of bupropion, but the Examiner required that all the claims be limited to HPMC as the release agent because the particular cellulose was considered critical. The district court ruled that because the claims had been limited during prosecution, the HPMC used in the example should restrict the scope of the claims. However, the Federal Circuit held that the HPMC was not limited to the grade and molecular weight of the HPMC in the specific examples. Rather, the Court ruled, the claims, correctly construed, require only that HPMC be present in the stated amount, and that the product have the release rate, duration, plasma levels, and other properties set forth in the claims.

Having construed the claims, the Federal Circuit found that infringement cannot be resolved adversely to Glaxo on the SJ record because, while Andrx argues that its release rate and plasma profile are different from those in the Glaxo claims, Andrx has represented the bioequivalence of its product.