This problematic reasoning was recognized by the Court of Appeals for the District of Columbia in another case involving Abbott and dealing with the definition of "active ingredient."⁷ The issue in Abbott centered on the period of market exclusivity granted for a new drug under 21 U.S.C. § 355(j)(4),⁸ which provided for a 10-year period of market exclusivity for a new "active ingredient." Valproic acid had been previously approved for marketing and was sold as Depakene.

Abbott argued that its novel disodium valproic was a new "active ingredient," and therefore entitled to 10-year market exclusivity. Because the federal market exclusivity provisions are part of the Act, but codified in different chapters of the US code, one might expect that the meaning of "active ingredient" should be consistent throughout the Act. However, the Abbott court, recognizing the problem that was engendered by reasoning in Glaxo, arrived at the opposite conclusion, ruling that "active ingredient" in the Act means "active moiety."

Had this definition of "active ingredient" been applied in the Glaxo case, the court could easily have concluded that the active ingredient, i.e., the active moiety, in cefuroxime axetil was the same as that in cefuroxime sodium, thus precluding patent term extension on the axetil form of the compound.

In summary, under the holding of the Glaxo court, a drug product based on a new salt or ester of a previously approved salt or ester drug product, may be eligible for a patent-term extension. Under the reasoning in Abbott, approval of a drug product in any form would seem to preclude patent-term extension on a subsequent product based on any other form of the same drug, that is, a drug having the same active moiety. However, to the extent the Glaxo decision is based on a misunderstanding of chemical forms of drug, it is likely to carry less validity in the future.

This shift toward the Abbott decision is reflected in Pfizer, Inc., v. Dr. Reddy's Laboratories, Ltd.⁹ The Pfizer court relied on the earlier Abbott decision and agreed that active ingredient means "active moiety," for purposes of determining what "product" is covered by a patent term extension. The Pfizer court ruled that a previous product approval and patent-term extension on a particular salt form of a drug encompassed alternative salt and ester forms of the drug.

Until this issue is resolved by the courts, it may nonetheless be prudent for a drug manufacturer in this situation to seek patent-term extension, arguing the reasoning derived from the Glaxo case. An applicant for a patent term extension should also search for arguments to demonstrate that the compounds in question are not the same "active moieties."

Judy M. Mohr, Ph.D. Perkins Coie, LLP, 101 Jefferson Drive Menlo Park, CA 94025, 650.838.4402,fax 650.838.4350, jmohr@perkinscoie.com

REFERENCES

1. Cardiac Pacemakers v. St. Jude Medical Inc., WL 483973 (S.D. Ind. 2001).

2. 35 U.S.C. § 156(a)(5).

3. 35 U.S.C. § 156(c)(4).

4. 35 U.S.C. § 156(a)(2).

5. Glaxo Operations UK Limited v. Quigg (894 F.2d 392 (Fed. Cir. 1990)).

6. 35 U.S.C. § 156 (f)(2).

7. Abbott Laboratories v. Young, 920 F.2d 989 (U.S. App. D.C. 1990).

8. 21 U.S.C. § 355(j)(4).

9. Pfizer Inc. v. Dr. Reddy's Laboratories, Ltd., 359 F.3d 1361 (Fed. Cir. 2004).