Infringement Under Doctrine of Equivalents Barred by Prosecution History Estoppel in CENESTIN Estrogen Therapy Case
The U.S. Court of Appeals affirmed a district court’s grant of summary judgment of noninfringement of an estrogen replacement drug patent, finding infringement under the doctrine of equivalents was barred by prosecution history estoppel.
Moisture Barrier Coating Amendment
Duramed Pharmaceuticals, Inc. (“Duramed”) is the owner of U.S. Patent No. 5,908,638 (the ’638 patent), relating to estrogen pharmaceutical compositions coated with a moisture barrier coating (“MBA”) for use in hormone replacement therapies. During prosecution, Duramed overcame an obviousness rejection by amending claim 1 to limit the MBA to “ethylcellulose.” Duramed markets its estrogen hormone replacement therapy product as CENESTIN. Paddock Laboratories, Inc. (“Paddock”) filed an Abbreviated New Drug Application (“ANDA”), seeking FDA approval to market a generic version of CENESTIN. Paddock’s proposed generic formulation, marketed as Opadry AMB, comprises a polyvinyl alcohol (“PVA”) MBA instead of ethylcellulose. In response, Duramed brought suit in the U.S. District Court for the Southern District of New York against Paddock, alleging infringement of claims 1, 4, and 6-8 of the ’638 patent under the doctrine of equivalents. Paddock moved for summary judgment of noninfringement, asserting that Duramed was barred by prosecution history estoppel from alleging that PVA met the ethylcellulose MBA limitation of the asserted claims.
The district court granted Paddock’s noninfringement summary judgment motion, finding that the amendment adding the ethylcellulose limitation was substantially related to patentability and narrowed the scope of the asserted claims, thus triggering the presumption of surrender for all equivalents under Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 344 F.3d 1359 (Fed. Cir. 2003) (en banc). The district court also held that Duramed failed to rebut the Festo presumption, finding that use of PVA as a MBA in a pharmaceutical composition was foreseeable at the time of the amendment.
Prosecution History Estoppel Bars Equivalence Infringement
The Federal Circuit affirmed the noninfringement summary judgment, finding prosecution history estoppel barred Duramed from asserting infringement under the doctrine of equivalents. The court noted that since Duramed narrowed the scope of claim 1 in response to a prior art rejection, a presumption of prosecution history estoppel applied. Additionally, the Federal Circuit found that Duramed failed to rebut the presumption by showing that the alleged equivalent would have been unforeseeable at the time of the amendment. Rejecting Duramed’s definition of the field of the invention restricting the suitability of PVA or Opadry AMB for use with conjugated estrogens, the Federal Circuit stated that when both original and issued claims begin “with the words ‘[a] pharmaceutical composition,’ that language defines the field of the invention for purposes of determining foreseeability.” Duramed at 7-8 (citing Schwarz Pharma, Inc. v. Paddock Labs., Inc., 504 F.3d 1371, 1377 (Fed. Cir. 2007)). Finding that an international patent application filed prior to the amendment pursuant to the Patent Cooperation Treaty (“PCT”) disclosed formulations of PVA MBAs, including Opadry AMB, the Federal Circuit concluded that such PVA MBAs were known in the field of the invention, and, thus foreseeable. The Federal Circuit clarified that “even 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.” Id. at 9. The court held that Duramed failed to rebut the presumption of prosecution history estoppel by showing that PVA MBCs would have been unforeseeable at the time of its narrowing amendment. Accordingly, the Federal Circuit affirmed the district court’s grant of summary judgment of noninfringement.
This document and any discussions set forth herein are for informational purposes only, and should not be construed as legal advice, which has to be addressed to particular facts and circumstances involved in any given situation. Review or use of the document and any discussions does not create an attorney-client relationship with the author or publisher. To the extent that this document may contain suggested provisions, they will require modification to suit a particular transaction, jurisdiction or situation. Please consult with an attorney with the appropriate level of experience if you have any questions. Any tax information contained in the document or discussions is not intended to be used, and cannot be used, for purposes of avoiding penalties imposed under the United States Internal Revenue Code. Any opinions expressed are those of the author. Bloomberg Finance L.P. and its affiliated entities do not take responsibility for the content in this document or discussions and do not make any representation or warranty as to their completeness or accuracy.
© 2011 Bloomberg Finance L.P. All rights reserved. Bloomberg Law Reports ® is a registered trademark and service mark of Bloomberg Finance L.P.