By Donald Zuhn --
In Duramed Pharmaceuticals, Inc. v. Paddock Laboratories, Inc., the Federal Circuit today affirmed a decision by the District Court for the Southern District of New York granting summary judgment of noninfringement to Paddock Laboratories, Inc. with respect to U.S. Patent No. 5,908,638. The '638 patent, which is assigned to Duramed, relates to a conjugated estrogen forumulation that includes a moisture barrier coating (MBC) (the claimed conjugated estrogens are extremely water sensitive and therefore highly susceptible to moisture degradation during storage).
During prosecution of the '638 patent, Duramed overcame an obviousness rejection by amending claim 1, which originally recited a conjugated estrogen pharmaceutical composition "coated with a moisture barrier coating," to incorporate the limitations of dependent claim 7, which frecited a moisture barrier coating comprising ethylcellulose. Claim 1 as issued recites (emphasis added):
1. A pharmaceutical composition in a solid, unit dosage form capable of oral administration for the hormonal treatment of peri-menopausal, menopausal and post-menopausal disorders in a woman comprising:
conjugated estrogens coated onto one or more organic excipients forming a powdered conjugated estrogen composition where said composition is substantially free of inorganic excipients and further comprises about 30-70% gel-forming organic excipient and about 30-70% non-gel forming organic excipient by weight and having less than about 2.5% free water by weight and greater than 2.5% total water wherein said solid unit dosage form is coated with a moisture barrier coating comprising ethylcellulose.
Seeking approval to market a generic version of Duramed's conjugated estrogen hormone replacement therapy Cenestin®, Paddock filed an Abbreviated New Drug Application (ANDA) with the FDA. In response to that ANDA filing, Duramed brought suit against Paddock for infringement of claims 1, 4, and 6-8 of the '638 patent under the doctrine of equivalents (Paddock's proposed generic uses a polyvinyl alcohol (PVA) MBC, marketed as Opadry AMB, instead of ethylcellulose). Paddock then moved for summary judgment of noninfringement, asserting that Duramed was barred by prosecution estoppel from alleging that PVA met the "moisture barrier coating comprising ethylcellulose" limitation of the asserted claims. In its motion for summary judgment, Paddock relied, in part, on an International publication (the Colorcon PCT) disclosing formulations of PVA-based MBCs, including Opadry AMB. The District Court granted Paddock's motion, holding that the amendment adding the ethylcellulose limitation was substantially related to patentability, this amendment narrowed the scope of the asserted claims, and that Duramed had surrendered all subject matter between the original and amended claim scope. The District Court also held that PVA MBCs were foreseeable at the time of the narrowing amendment based on, inter alia, the prior art disclosure of both PVA as "a moisture barrier coating for pharmaceutical tablets" and the Opadry AMB formulation used by Paddock.
In an opinion authored by Judge Lourie and joined by Judges Gajarsa and Dyk, the Federal Circuit noted that because Duramed narrowed the scope of claim 1 in response to a prior art rejection, a presumption of prosecution history estoppel applied. The Court also noted that Duramed could attempt to rebut this presumption by showing that the alleged equivalent would have been unforeseeable at the time of the amendment. Duramed argued on appeal that PVA MBCs were not foreseeable because the relevant art did not disclose either PVA or Opadry AMB as suitable MBCs for moisture-sensitive pharmaceutical compounds, such as conjugated estrogens. The Court noted, however, that "to the extent that Duramed argues that foreseeability requires that PVA must have been known as an MBC for use with conjugated estrogens, we have previously rejected such a restrictive definition of the field of invention." The Court then determined that "the Colorcon PCT discloses PVA MBCs, including Opadry AMB, in the field of pharmaceutical compositions, rendering such PVA MBCs 'known in the field of the invention,' and thus foreseeable."
In response to Duramed's argument that the Colorcon PCT fails to establish that PVA-based Opadry AMB was suitable as an MBC because it provides only conclusory statements that the inventors had solved the technical drawbacks of PVA MBCs, the Federal Circuit noted that "foreseeability does not require such precise evidence of suitability," adding that:
[E]ven if the PCT disclosure indicates that PVA is less than ideal in some pharmaceutical uses as an MBC, it is still disclosed to be useful as such, and that renders it foreseeable for purposes of prosecution history estoppel. Foreseeability does not require flawless perfection to create an estoppel.
Finding that Duramed had failed to show that PVA MBCs would have been unforeseeable at the time of its narrowing amendment, the Federal Circuit affirmed the District Court's grant of summary judgment of noninfringement.
Duramed Pharmaceuticals, Inc. v. Paddock Laboratories, Inc. (Fed. Cir. 2011)
Panel: Circuit Judges Lourie, Gajarsa, and Dyk
Opinion by Circuit Judge Lourie