Duramed Pharms., Inc. v. Paddock Labs., Inc., No. 2010-1419 (Fed. Cir. 2011)
CENESTIN is a conjugated estrogen pharmaceutical composition used to reduce the symptoms of menopause. In a 3-0 decision last week, the Federal Circuit affirmed that Paddock's generic version of CENESTIN would not infringe U.S. Patent No. 5,908,638, directed to conjugated estrogen compositions, under the Doctrine of Equivalents.
Claim 1 of the '638 patent recites:
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.
In 2008, Paddock filed an ANDA for a generic version of CENESTIN, after which Duramed filed suit for infringement of the '638 patent. Duramed asserted infringement of independent claim 1 and dependent claims 4 and 6-8 under the doctrine of equivalents only.
In an opinion last year, District Judge Sand (S.D.N.Y.) concluded on summary judgment that the four asserted claims were not infringed under the doctrine of equivalents due to prosecution history estoppel. During prosecution, claim 1 originally recited a conjugated estrogen pharmaceutical composition "coated with a moisture barrier coating" (MBC). Original dependent claim 7 limited "said moisture barrier coating" to one that "comprises ethylcellulose." After initially rejecting both claims as obvious, the examiner later advised that he would allow the application if Duramed amended claim 1 to include the limitations of claim 7. In response, Duramed amended claim 1 to recite pharmaceutical compositions with "a moisture barrier coating comprising ethylcellulose."
Judge Sand concluded that the amendment adding the ethylcellulose limitation was substantially related to patentability and narrowed the claim scope, thus triggering the Festo presumption that Duramed had surrendered all territory between the original and amended claim scope (i.e., between "coated with a moisture barrier coating" and coated with a moisture barrier coating "comprising ethylcellulose"). Judge Sand also concluded that Duramed had failed to rebut the Festo presumption based on an argument of the unforeseeability of the use of polyvinyl alcohol (PVA) MBC, used in Paddock's proposed generic product and marketed as Opadry AMB. Judge Sand concluded that PVA MBCs were foreseeable at the time of Duramed's narrowing amendment (December 1998) because, among other things: (1) a Colorcon PCT application published in January 1996 described PVA as "a moisture barrier coating for pharmaceutical tablets and the like"; (2) pre-September 1996 invoices existed for the sale (by Colorcon) of Opadry AMB; and (3) a 1976 patent to Groppenbächer disclosed the use of PVA in moisture-tight tablets.
In affirming, the Federal Circuit noted that Duramed could rebut the presumption of prosecution history estoppel by showing that the alleged equivalent would have been unforeseeable at the time of the amendment and was thus beyond a fair interpretation of what was surrendered. Duramed argued that the district court applied the wrong legal test for foreseeability, and that an equivalent is not foreseeable unless it was understood by one of ordinary skill to be suitable for use in the invention as originally claimed. But the Federal Circuit rejected Duramed's arguments.
Duramed argued that foreseeability requires that PVA must have been known as an MBC for moisture-sensitive pharmaceutical compounds, like the claimed conjugated estrogens. Relying on Schwarz Pharma, Inc. v. Paddock Labs., Inc., 504 F.3d 1371, 1377 (Fed. Cir. 2007), the Federal Circuit stated that when the language of the original and issued claims begins with the words "[a] pharmaceutical composition," that language (and not merely the specifically-claimed constituent ingredient (here, conjugated estrogens)) defines the field of the invention for purposes of determining foreseeability. Accordingly, PVA MBCs need only to have been known in the field of pharmaceutical compositions, as of the time of Duramed's narrowing amendment. Because the Colorcon PCT discloses PVA MBCs, including Opadry AMB, in the field of pharmaceutical compositions, such PVA MBCs were "known in the field of the invention," and thus foreseeable. Thus, the Federal Circuit held that the Colorcon PCT established foreseeability as a matter of law.
The Federal Circuit also explained that "foreseeability does not require . . . precise evidence of suitability. . . . Foreseeability does not require flawless perfection to create an estoppel." Thus, the Federal Circuit rejected Duramed's arguments that the Colorcon PCT did not establish foreseeability due to its inclusion of (1) technical drawbacks, and (2) conclusory statements, rather than test data showing precise characteristics or precise suitability.
Finally, the Federal Circuit held that no genuine issue of fact precluded a finding that a December 1995 article in the scientific journal "Manufacturing Chemist" was publicly available to assess foreseeability. In reaching this conclusion, the Federal Circuit emphasized that the amendment date (December 1998), not the application date (July 1995), was the pertinent time for determining foreseeability.
Comments