Prosecution History Estoppel Bars Allegations of Infringement Under Doctrine of Equivalents
Duramed v. Paddock (decided 7/21/11)By: Heather J. DiPietrantonio
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What This Means to You
- Keep in mind post-filing, pre-amendment art when introducing claim limitations during prosecution.
- Consider disclosing in the specification and then claiming alternative embodiments with different degrees of specificity.
- Provide dependent claims with incrementally narrower scope for critical claim terms.
- Consider functional claim limitations to broaden scope.
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Overview
In Duramed Pharmaceuticals, Inc. v. Paddock Laboratories, Inc., the US Court of Appeals for the Federal Circuit (Federal Circuit) confirmed that claim amendments introduced during prosecution to overcome prior art bar allegations of infringement under the doctrine of equivalents.
The Federal Circuit decision also raised several questions relating to “foreseeability” of amendments, including how language in the preamble of a claim defines the scope of the claim.
Case Background
Duramed Pharmaceuticals obtained a patent to a pharmaceutical composition of conjugated estrogens for use in hormone replacement therapies. During prosecution of the patent, Duramed amended the independent composition claim to overcome prior art. The amended claim required a moisture barrier coating comprising ethylcellulose.
Paddock Laboratories filed an Abbreviated New Drug Application (ANDA) for a generic version of Duramed’s pharmaceutical composition. Paddock’s composition comprised polyvinyl alcohol (PVA) as a moisture barrier coating, not ethylcellulose.
Duramed sued Paddock alleging infringement of its patent under the doctrine of equivalents, which states that a product/process can still infringe if there is “equivalence” between its elements and the claimed elements of the patented invention. Paddock’s motion for summary judgment argued that Duramed was barred by prosecution history estoppel from asserting that PVA met the “moisture barrier coating comprising ethylcellulose” claim limitation. Prosecution history estoppel prevents a patent owner from using the doctrine of equivalents to recapture subject matter it surrendered during prosecution.
The district court granted summary judgment of noninfringement to Paddock, and Duramed appealed to the Federal Circuit.
Decision Analysis
In its decision, the Federal Circuit took the position that because Duramed narrowed the scope of its patent’s claims in response to a prior art rejection, a presumption of prosecution history estoppel applied, thus PVA was not considered an equivalent. The court reasoned that purported equivalent PVA was foreseeable before the time of the amendment.
Takeaways
This case highlights the importance of using great care when considering the introduction of limitations into claims during prosecution. This means, in part, keeping in mind post-filing, pre-amendment art when introducing claim limitations during prosecution.
In addition, you should consider disclosing in the specification and claiming alternatives with different degrees of specificity to help overcome the prosecution history estoppel issues in this case. You may also wish to consider providing dependent claims with incrementally narrower scope when you have critical claim terms.
Lastly, consider functional limitations to broaden the scope of your claims.
