Ajinomoto Co. v. International Trade Commission

Ajinomoto Co. (plaintiff) sought a patent that covered (1) E. coli bacteria genetically engineered to increase the production of L-amino acids and (2) methods of producing such L-amino acids using the bacteria. In the patent application, claim 1 recited two alternatives for the claimed protein being protected. The examiner for the United States Patent and Trademark Office rejected the second alternative, finding that it encompassed a protein that was anticipated by prior art. In response, Ajinomoto amended the second alternative to narrow the scope of the proteins covered. The examiner then issued the patent. Claim 9 described an E. coli bacterium able to accumulate L-amino acids in a medium after L-amino-acid production was increased beyond normal levels by a protein in a specified amino-acid sequence. Ajinomoto later filed a complaint against CJ CheilJedang Corp. and affiliates (CJ) (defendants) with the International Trade Commission (commission) (defendant), alleging that CJ was importing certain products that infringed Ajinomoto’s patent. The commission determined, among other things, that one of CJ’s strains of E. coli infringed claim 9 of the patent. The commission relied on the doctrine of equivalents. It concluded that although CJ’s strain used a different DNA sequence to encode the relevant protein and therefore did not literally infringe the patent, the strain nevertheless constituted infringement because the difference from protected strains was insubstantial. CJ and Ajinomoto both appealed the commission’s decision. CJ argued that prosecution-history estoppel precluded reliance on the doctrine of equivalents because, by narrowing claim 1 in the patent-application process, Ajinomoto disclaimed all things falling between the original patent claim and the amended patent claim, including CJ’s strain.