Claims Define Broad Field of Forseeability for Equivalents Analysis
- "A pharmaceutical composition. . ." and
- "A process for stabilizing an ACE inhibitor drug against cyclization which comprises the step of contacting the drug with . . .",
. . . With respect to amendment-based estoppel, the Supreme Court has stated:A patentee’s decision to narrow his claims through amendment may be presumed to be a general disclaimer of the territory between the original claim and the amended claim. There are some cases, however, where the amendment cannot reasonably be viewed as surrendering a particular equivalent. The equivalent may have been unforeseeable at the time of the application; the rationale underlying the amendment may bear no more than a tangential relation to the equivalent in question; or there may be some other reason suggesting that the patentee could not reasonably be expected to have described the insubstantial substitute in
question. In those cases the patentee can overcome the presumption that prosecution history estoppel bars a finding of equivalence.
Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 535 U.S. 722, 740-41 (2002).
As the quoted passage from Festo above indicates, it is Schwarz’s burden to rebut the presumption that MgO was surrendered as an equivalent when the claims of the ’450 patent were amended. As to foreseeability, this court recently held that "an alternative is foreseeable if it is known in the field of the invention as reflected in the claim scope before amendment" and that it would be inappropriate to apply an insubstantial differences or function/way/result test in order to determine foreseeability. Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., Ltd., 493 F.3d 1368, 1379 (Fed. Cir. 2007). On appeal, Schwarz does not seriously dispute that MgO was known as a stabilizer by those of skill in the art at the time of the amendment, but rather insists that MgO had to have been known as a stabilizer against the specific degradation pathway of cyclization or for the specific drug category of ACE inhibitors in order to have been foreseeable as an equivalent. We disagree.
While care must be taken not to sweep too broadly in defining the field of an invention, Schwarz attempts to define the field of invention too narrowly. The language of original claim 1 (and that of issued claim 1 as well) began with the words "[a] pharmaceutical composition which contains," and the language of a claim defining an invention defines the field within which foreseeability may be considered. The scope of the claim thus supports the district court’s treatment of the field of invention as pharmaceutical compositions rather than being limited to pharmaceutical stabilizers that inhibit cyclization in ACE inhibitors. We therefore conclude that, because MgO was known as a stabilizer in the field of pharmaceutical compositions, Schwarz has failed to rebut the presumption of surrender by demonstrating that MgO was not a foreseeable equivalent.
As for claim 16, a process claim, it recites a process for stabilizing an ACE inhibitor drug against cyclization. Given the prior art that discloses that MgO is a stabilizer, it does not require much of a stretch of the imagination of a person skilled in the art of pharmaceutical formulation to foresee that that stabilizer might be helpful in stabilizing ACE inhibitors.