## Facts

- Ajinomoto owned U.S. Patent No. 7,666,655, directed to genetically engineered *E. coli* with increased production of aromatic L-amino acids (including L-tryptophan) and methods using such bacteria.
- The patent disclosed the *yddG* gene and its encoded membrane transporter protein (YddG) as involved in amino-acid export.
- CJ produced L-tryptophan abroad using multiple engineered *E. coli* strains and imported the resulting products into the United States.
- Ajinomoto filed an ITC complaint under § 337 alleging CJ’s imported products were made by processes infringing the patent, focusing on claim 9 (an *E. coli* bacterium capable of accumulating L-amino acid due to increased expression of a structurally defined protein).
- The ALJ construed the claims and found no infringement (literal or under the doctrine of equivalents) and invalidity for lack of written description under 35 U.S.C. § 112(a).
- On review, the Commission adopted a different outcome: CJ’s earlier strains did not infringe, CJ’s two later strains did infringe (at least claim 9) under the doctrine of equivalents, and the asserted claim was not invalid for inadequate written description.
- One later CJ strain used a different DNA sequence encoding a transporter protein that was not literally within the claim as construed but performed the same export function with insubstantial differences.

## Issues

1. Whether the Commission correctly construed the structural limitations of claim 9 concerning the transporter protein.
2. Whether substantial evidence supported findings of noninfringement for earlier strains and infringement for later strains, including infringement under the doctrine of equivalents.
3. Whether prosecution history estoppel, arising from narrowing amendments during prosecution, barred Ajinomoto’s doctrine-of-equivalents theory for the later strains.
4. Whether the asserted claim lacked adequate written description under 35 U.S.C. § 112(a).

## Decision

- The Federal Circuit affirmed the Commission’s claim construction.
- The court affirmed the determination that CJ’s earlier strains did not infringe.
- The court affirmed the determination that CJ’s later strains infringed claim 9 under the doctrine of equivalents.
- The court rejected CJ’s argument that prosecution history estoppel categorically barred Ajinomoto’s equivalents theory for the later strains.
- The court affirmed the Commission’s finding that the asserted claim satisfied the written description requirement.
- Judge Dyk concurred in part and dissented in part, concluding that estoppel should bar the doctrine-of-equivalents finding as to the later strains.

## Legal Principles

- Claim construction is reviewed de novo for legal conclusions, with deference to supported subsidiary factual findings.
- Doctrine of equivalents infringement may be found when differences between the accused element and the claimed element are insubstantial, including under a function–way–result analysis.
- A narrowing amendment made for patentability reasons can trigger prosecution history estoppel, but the estoppel scope is limited to what the patentee actually surrendered; it does not automatically bar all equivalents between original and amended claim language.
- Written description under § 112(a) requires the specification to reasonably convey to skilled artisans that the inventor possessed the claimed subject matter as of the filing date; adequacy is evaluated in view of the properly construed claim.

## Conclusion

The Federal Circuit upheld the ITC’s determination that the asserted claim of Ajinomoto’s biotechnology patent was adequately described, that CJ’s earlier strains did not infringe, and that CJ’s later strains infringed under the doctrine of equivalents because the sequence differences were insubstantial and not barred by prosecution history estoppel.


Ajinomoto Co. v. Int'l Trade Comm'n, 932 F.3d 1342 (Fed. Cir. 2019)