Addressing whether an amendment narrowing the claim scope during the prosecution limited the patentee’s ability to capture a generic’s different, but potentially equivalent, product as infringing, the U.S. Court of Appeals for the Federal Circuit affirmed a decision on summary judgment, finding that prosecution history estoppel applied and barred the application of the doctrine of equivalents (DOE).  Duramed Pharmaceuticals, Inc. (Teva Women’s Health) v. Paddock Laboratories, Inc., Case No. 10-1419 (Fed. Cir., July 21, 2011 (Lourie, J.).

In this Abbreviated New Drug Application (ANDA) litigation, to prevent Paddock from marketing a generic version of Duramed’s (now Teva Women’s Health) conjugated estrogen pharmaceutical composition (Cenestin) for hormone replacement therapy, Duramed asserted a patent having claims directed to pharmaceutical compositions comprising conjugated estrogens in a solid dosage form coated with a moisture-barrier coating comprising ethylcellulose.  Because Paddock’s ANDA indicated that it planned on using conjugated estrogen pharmaceutical compositions with a barrier made of polyvinyl alcohol, rather than ethylcellulose, Duramed sued Paddock for patent infringement under the DOE.  The district court granted Duramed’s motion for summary judgment of non-infringement, finding that the narrowing of the claims to recite a particular moisture barrier coating in view of the prior art was substantially related to patentability and, therefore, under Festo, a presumption of prosecution history estoppel applied.  The district court further found that Duramed had not overcome this presumption, and thus the DOE could not be applied, because the prior art illustrated that polyvinyl alcohol moisture barriers were foreseeable.  Duramed appealed.

The Federal Circuit affirmed, agreeing with the district court that, under Festo, because Duramed narrowed the scope of the claims during prosecution, a presumption of prosecution history estoppel applied.  The Federal Circuit also agreed with the district court that Duramed had failed to rebut this presumption.  Specifically, the Court found Duramed’s argument that foreseeability required that polyvinyl alcohol must have been known for use with conjugated estrogens unconvincing.  Rather, citing its decision in Schwarz, the Court noted that “when the language of both the original and issued claims begins with the words ‘[a] pharmaceutical composition,’ that language defines the field of the invention for purposes of determining foreseeability.”  Accordingly, the Court concluded that polyvinyl alcohols as a moisture barrier need only to have been known in the field of pharmaceutical compositions at the time of the amendment.  Citing prior art submitted by Paddock disclosing the use of polyvinyl alcohol as a moisture-barrier coating in pharmaceutical compositions, the Court found that it was foreseeable by Duramed that this composition could have been used as a moisture barrier instead of ethylcellulose and, by amending the claims to require ethylcellulose, Duramed has surrendered this foreseeable equivalent.