In an en banc, sua sponte opinion in Lupin Ltd. and Lupin Pharmaceuticals Inc. v. Abbott Laboratories and Astellas Pharma, Inc., No. 2007-1446 (Fed. Cir. May 18, 2009) the Federal Circuit held that process terms in product-by-process claims serve as limitations in determining infringement. In so holding, the Federal Circuit resolved its own long-standing conflict on this point, agreeing with the panel decision in Atlantic Thermoplastics Co., Inc. v. Faytex Corp., 970 F.2d 834 (Fed. Cir. 1992). The court expressly overruled Scripps Clinic & Research Found. v. Genetech, Inc. 927 F.2d 1565 (Fed. Cir. 1991) holding that process terms are not considered to be claim limitations for determining infringement.

Astellas owns U.S. Patent No. 4,935,507 and licenses it to Abbott. The '507 patent has certain claims directed to the crystalline antibiotic cefdinir made by a recited process. Lupin did not employ the claimed process to make its cefdinir. Accordingly, the court affirmed the Eastern District of Virginia's grant of partial summary judgment of non-infringement. The court combined the Lupin case with a related dispute involving the '507 patent in the Northern District of Illinois between Abbott and Astellas and several other generic drug manufacturers. The parties in the Illinois case agreed to be bound by the Virginia court's claim construction. While not relying on its holding regarding product-by-process claims, the Federal Circuit affirmed the Northern District's denial of Abbott's request for a preliminary injunction. Abbott Laboratories et al. v. Sandoz, Inc. et al., No. 2007-1400 (Fed. Cir. May 18, 2009).

In overruling Scripps, the Federal Circuit noted that the conflicting decision in Atlantic Thermoplastics found "extensive support in Supreme Court opinions that have addressed the proper reading of product-by-process claims" stating that in each of those cases "the Supreme Court consistently noted that process terms that define the product in a product-by-process claim serve as enforceable limitations." Lupin, slip op. at 15. The court also cited similar holdings in both its predecessor court, the Court of Customs and Patent Appeals, and sister circuit courts. Id. at 15-16. Citing Warner-Jenkensin Co. v. Hilton Davis Chemical Co., 520 U.S. 17, 19 (1997), the court further observed that its decision is consistent with the "broad principle that '[e]ach element contained in a patent claim is deemed material to defining the scope of the patented invention.'" Id. at 18.

The Federal Circuit’s decision in Lupin makes clear that a party can avoid infringing a product-by-process claim, such as “product X, obtained by process Y,” by using a process to make product X that is substantially different from process Y. The Federal Circuit certainly recognized that an inventor is free to define a product by the process by which it is made. The inventor can avoid having to prove that the alleged infringing product was made by the claimed process, however, by including claims describing the product by its structure, properties, or other characteristics, if the prior art permits.