Recent Federal Circuit decisions demonstrate that the doctrine of equivalents is alive and well, and not always barred by claim amendments. In both Ajinomoto Co. v. ITC and Eli Lilly and Co. v. Hospira, Inc., the Federal Circuit found the claim amendments at issue to be “tangential” to the “equivalent” at issue, and upheld findings of infringement.

The Ajinomoto Decision 

The Ajinomoto opinion was written by Judge Taranto and joined by Judge Moore. Judge Dyk dissented.

The patent at issue was U.S. Patent No. 7,666,655. Asserted claim 20 was a multiply dependent claim that put claims 9 and 15 in issue:

20.  A  method for producing an aromatic L-amino acid, which comprises cultivating the bacterium according to any one of claims 9–12, 13, 14, 15–18, or 19.

9.  A recombinant Escherichia coli bacterium which has the ability to accumulate aromatic L-amino acid in a medium, wherein the aromatic L-amino acid production by said bacterium is enhanced by enhancing activity of a protein in a cell of said bacterium beyond the levels observed in a wild-type of said bacterium,
and in which said protein consists of the amino acid sequence of SEQ ID NO: 2
and said protein has the activity to make the bacterium resistant to L-phenylalanine, fluorophenylalanine or 5[-]fluoro-DL-tryptophan,
wherein the activity of the protein is enhanced by [3a] transformation of the bacterium with a DNA encoding the protein to express the protein in the bacterium, [3b] by replacing the native promoter which precedes the DNA on the chromosome of the bacterium with a more potent promoter, [3c] or by introduction of multiple copies

The Federal Circuit explained that “[c]laim 15 is materially identical to claim 9,” except the protein limitation refers to the encoding nucleotide sequence and SEQ ID NO:1.

The ITC found infringement of claim 20 under the claim 9 alternative, based on a determination that the accused YddG protein encoded by a codon-randomized non-E. coli yddG gene was an equivalent of SEQ ID NO:2 (which is the amino-acid sequence of the E. coli YddG protein).

The claim amendment at issue related to the claim 15 language referring to the encoding nucleotide sequence. The original claim language recited “a protein which comprises an 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,” and was replaced with “a protein which comprises 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.”

The Federal circuit agreed with the ITC’s determination that the amendment was “tangential” to the equivalent at issue:

The objectively evident rationale for the amendment was to limit the set of proteins within the claim’s scope so that it no longer included the prior-art E. coli YfiK protein and, more generally, no longer allowed as wide a range of amino acid alterations …. The reason for the amendment had nothing to do with choosing among several DNA sequences in the redundant genetic code that correspond to the same protein.

Thus, the Federal Circuit agreed that prosecution history estoppel did not bar application of the doctrine of equivalents.

The Eli Lilly Decision

The Eli Lilly opinion was written by Judge Lourie and joined by Judge Moore and Judge Taranto. 

The patent at issue was U.S. Patent No. 7,772,209, which is listed in the Orange Book for Eli Lilly’s Alimta® pemetrexed product. The court identified claim 12 as representative:

12. An improved method for administering pemetrexed disodium to a patient in need of chemotherapeutic treatment, wherein the improvement comprises:
a) administration of between about 350 µg and about 1000 µg of folic acid prior to the first administration of pemetrexed disodium;
b) administration of about 500 µg to about 1500 µg of vitamin B12, prior to the first administration of pemetrexed disodium; and
c) administration of pemetrexed disodium.

The amendment at issue had amended claim language reciting administering an “antifolate” to instead recite administering “pemetrexed disodium,” to overcome a prior art rejection based on a reference disclosing the use of methotrexate.

The accused ANDA products contained pemetrexed ditromethamine, not pemetrexed disodium. Nevertheless, the district court found infringement under the doctrine of equivalents. The Federal Circuit agreed that prosecution history estoppel did not bar such a finding, because the amendment was “tangential” to the equivalent at issue:

[T]he particular type of salt to which pemetrexed is complexed relates only tenuously to the reason for the narrowing amendment, which was to avoid Arsenyan. We therefore hold that Lilly’s amendment was merely tangential to pemetrexed ditromethamine because the prosecution history, in view of the ’209 patent itself, strongly indicates that the reason for the amendment was not to cede other, functionally identical, pemetrexed salts. …. The prosecution record implies that Lilly’s amendment, inartful though it might have been, was prudential in nature and did not need or intend to cede other pemetrexed salts.

In rejecting Hospira’s arguments, the court emphasized the fact-specific nature of the determination, and concluded that “on this prosecution record” the “amendment was merely tangential to pemetrexed ditromethamin.”

Relying On the Doctrine of Equivalents Can Still Be Dangerous

Although these patentees were able to establish infringement under the doctrine of equivalents, the cases distinguished in the Federal Circuit decisions remind that relying on the doctrine of equivalents can be dangerous. Indeed, Judge Dyk dissented from the majority decision in Ajinomoto:

The problem with the majority’s analysis is that it ignores how the patentee deliberately elected to narrow the claims. The anticipating prior art disclosed E. coli YfiK protein, encoded by the yfiK gene, and this prior art was avoided by narrowing the claim to only cover certain encoding nucleotide sequences. That rationale is directly related to the accused equivalent, which does not infringe because it does not use a covered encoding nucleotide sequence. In other words, the rationale for the narrowing amendment (avoiding a prior art protein based on its encoding nucleotide sequence that does not meet the newly claimed hybridization requirement) directly relates to the accused equivalent (a protein made by an encoding nucleotide sequence that does not meet the newly claimed hybridization requirement).

In providing this explanation, Judge Dyk seems to be advocating the “bright line rule” rejected in Eli Lilly, that “where the reason for the amendment and the equivalent in question both relate to the same claim element, the tangential exception does not apply.”