Before Dyk, Moore, and Taranto. Appeal from the ITC.

Ajinomoto filed a complaint against CJ America, Inc. with the International Trade Commission (“ITC”), alleging that CJ used several strains of E-coli bacteria to make products imported into the United States that infringed its patent. The ITC determined that two of CJ’s E-coli strains infringed the asserted patent under the doctrine of equivalents. The ITC found that Ajinomoto did not surrender the equivalent during prosecution because the “tangential relation” exception applied. CJ appealed.

Claim 1 originally recited a protein defined as either (A) comprising the amino acid sequence shown in SEQ ID NO:2; or (B) comprising the amino acid sequence including deletion, substitution, insertion or addition of one or several amino acids in the amino acid sequence shown in SEQ ID NO:2. Claim 1 was rejected as anticipated by a reference that disclosed the language of (B), but not (A). The language of (B) was amended to overcome the reference and instead recite: “an amino acid sequence that is encoded by a nucleotide sequence that hybridizes with the nucleotide sequence of SEQ ID NO:1 under stringent conditions.” Later during prosecution, Claims 9 and 15 were subsequently added, with Claim 9 including the language of (A) and Claim 15 including the language of amended (B).

CJ’s E-coli strains did not include the precise amino acid sequence required by the language of (A). Ajinomoto argued that CJ nevertheless infringed under the doctrine of equivalents. CJ argued that the amendment of (B) created prosecution history estoppel on the language of (A). While never reaching the question of whether prosecution history applied at all, the Federal Circuit disagreed. Under the tangential relation exception, the question is “whether the reason for the narrowing amendment was peripheral, or not directly relevant, to the alleged equivalent.” Here, the Federal Circuit held that the reason for the narrowing amendment was limiting the amino-acid makeup of the proteins included in one of the alternatives covered by the claim. This reason was unrelated to choosing the DNA sequences that encode a given protein. Accordingly, there was no surrender of the equivalent by the amendment to (B).

Judge Dyk dissented in part on the ground that the tangential relation exception did not apply because the equivalent was directly related to the reason for the amendment.