## Facts

- Two related patents covered stable injectable acetaminophen formulations and methods to reduce oxygen to improve stability: U.S. Patent No. 6,028,222 (composition) and U.S. Patent No. 6,992,218 (method).
- Cadence marketed FDA-approved injectable acetaminophen (Ofirmev®), with both patents listed in the Orange Book for that product.
- Exela filed an ANDA seeking approval for a generic version and submitted a Paragraph IV certification asserting the patents were invalid and not infringed.
- The ’222 patent’s key limitation required an aqueous acetaminophen formulation containing “a buffering agent” (and other components).
- The ’218 patent claimed a process including a “vacuum stoppering step” to achieve oxygen concentrations below 2 ppm.
- In a Hatch–Waxman action in the District of Delaware, after a bench trial the court found: (i) literal infringement of asserted ’222 claims and no invalidity; (ii) infringement of asserted ’218 claims under the doctrine of equivalents and failure to prove invalidity (including obviousness).
- Exela appealed, contesting claim constructions, infringement findings, and the non-obviousness determination for the ’218 patent.

## Issues

1. Under the post-*Teva* standard, what deference is owed to a district court’s subsidiary factual findings underlying claim construction?
2. Whether “buffering agent” in the ’222 patent should be given its ordinary meaning or narrowed by the specification or accused product characteristics.
3. Whether “vacuum stoppering step” in the ’218 patent should be narrowly limited to particular equipment/protocols or construed functionally in light of the specification.
4. Whether Exela’s ANDA product literally infringed the ’222 patent and whether Exela’s process infringed the ’218 patent under the doctrine of equivalents.
5. Whether Exela proved the asserted ’218 claims were obvious by clear and convincing evidence.

## Decision

- The Federal Circuit affirmed the district court in all respects.
- Applying *Teva*, the court reviewed subsidiary factual findings for clear error and the ultimate claim constructions de novo, finding no reversible error.
- The construction of “buffering agent” as consistent with its ordinary meaning in chemistry was affirmed; the court rejected importing additional limitations from the specification or the accused product.
- Based on that construction, the finding that Exela’s formulation met the “buffering agent” limitation and literally infringed the ’222 patent was affirmed.
- The construction of “vacuum stoppering step” tied to removing oxygen from vial headspace using a vacuum (without restricting to a specific apparatus or sequence) was affirmed.
- The finding of infringement of the ’218 patent under the doctrine of equivalents was affirmed, relying on credited expert testimony that differences were insubstantial for achieving very low oxygen levels.
- The determination that Exela failed to prove the ’218 claims obvious was affirmed; the district court’s factual findings were not clearly erroneous.

## Legal Principles

- After *Teva*, subsidiary factual findings based on extrinsic evidence used in claim construction are reviewed for clear error, while the ultimate claim construction remains a legal question reviewed de novo.
- Claim terms are generally given their plain and ordinary meaning absent a clear disclaimer or lexicography; courts should not import limitations from embodiments, examples, or the accused product into the claims.
- Doctrine-of-equivalents infringement may be found for process claims when the accused method performs substantially the same function in substantially the same way to obtain substantially the same result, supported by record evidence and expert testimony.
- Patent invalidity for obviousness must be proven by clear and convincing evidence, and appellate review gives deference to district-court factual findings unless clearly erroneous.

## Conclusion

The Federal Circuit upheld ordinary-meaning claim constructions under *Teva*, affirmed findings of literal infringement and doctrine-of-equivalents infringement in an ANDA case, and sustained the patents against an obviousness challenge due to the absence of clear and convincing proof and the deference owed to supported factual findings.


Cadence Pharms. Inc. v. Exela Pharmsci Inc., 780 F.3d 1364 (Fed. Cir. 2015)