Federal Circuit Again Rules Equivalent Foreseeable in Duramed

Back in the “good ol’ days,” the Supreme Court rarely granted review of a Federal Circuit case involving patent law doctrines.  One such “rare” instance where the Supreme Court did review (and partially affirmed and partially overturned the Federal Circuit) was the 2002 case of Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. involving when the doctrine of prosecution history estoppel barred an assertion of patent infringement based on the doctrine of equivalents when there was any amendment that narrowed the patent claim at issue.”  See When Patent Doctrines Collide:  Supreme Court Rules Claim Amendments Do Not Necessarily Preclude Assertion of Infringing Equivalents.

Like the most recent run of decisions overturning Federal Circuit patent jurisprudence, the Supreme Court found, in Festo, that the Federal Circuit’s rule that, whenever prosecution history estoppel applied, there would be no range of equivalents for the amended element, was too “inflexible” for the High Court’s taste.

Instead, the Supreme Court found there were two exceptions to “prosecution history estoppel is a bar to the doctrine of equivalents” rule:  (1) the equivalents asserted are “unforeseeable at the time of the amendment and beyond a fair interpretation of what was surrendered;” or (2) the aspect of the invention in question has “only a peripheral relation to the reason the amendment” was made.  The first exception (“unforseeability of the equivalent”) has always astonished and annoyed me.  How can an equivalent which is “unforeseeable” (and thus in conflict with the requirements of 35 U.S.C. § 112, first paragraph and potentially sixth paragraph) be an equivalent for the purposes of avoiding prosecution history estoppel?  But as patentees have found out, this “unforseeability” exception has proved to be an unavailing canard, as witnessed (again) in Duramed Pharmaceuticals, Inc. v. Paddock Laboratories, Inc.


In Duramed, the invention claimed in U.S. Pat. No. 5,908,638 (the “’638 patent”) involved a conjugated estrogen pharmaceutical compositions for use in hormone replacement therapies. The critical aspect of the claimed invention was the moisture barrier coating (MBC) which surrounded the composition. Claim 7 (which depended from independent Claim 1) specified that this MBC “comprises ethylcellulose.”  During patent prosecution, the examiner rejected both Claims 1 and 7 for obviousness under 35 U.S.C. § 103.  As a result of an interview with the examiner, Claim 1 was amended to include the recitation in Claim 7, and in due course, the ‘638 patent issued. Sounds to me like a classical instance of prosecution history estoppel coming into play and barring any application of the doctrine of equivalents.

In March 2009, Duramed (the patentee) filee suit against Paddock (the alleged infringer) under 35 U.S.C. § 271(e)(2), alleging infringement of the ’638 patent based on Paddock’s Abbreviated New Drug Application (“ANDA”) for a generic version of Duramed’s hormone replacement therapy product, Cenestin®.

Instead of ethylcellulose, Paddock used a very different compound, polyvinyl alcohol (PVA), in the MBC of its generic drug, Opadry AMB.  Not surprisingly, Paddock moved for summary judgment of noninfringement, arguing that Duramed was barred by amendment-based prosecution history estoppel from alleging that PVA met the “moisture barrier coating comprising ethylcellulose” limitation of the asserted claims, including amended Claim 1.  Even less surprising to me, the district court granted summary judgment of noninfringement in favor of Paddock.

On appeal to the Federal Circuit, Duramed argued that the district court “applied the wrong legal test for foreseeability” based on the principle that “any mention of an alleged equivalent in the prior art makes that equivalent foreseeable as a matter of law.”  Instead, Duramed asserted that an equivalent isn’t foreseeable “if it was not understood by one of ordinary skill in the art to be suitable for use in the invention as originally claimed.”  Duramed further asserted that “the relevant art did not disclose either PVA or Opadry AMB as suitable MBCs for moisture-sensitive pharmaceutical compounds, like conjugated estrogens.”

Judge Lourie, writing for the Federal Circuit panel, didn’t buy Duramed’s assertions or argument.  Instead, Lourie’s opinion rejected Duramed’s assertion that “foreseeability requires that PVA must have been known as an MBC for use with conjugated estrogens (emphasis in the original),” noting that “we have previously rejected such a restrictive definition of the field of invention,” citing the 2007 case of Schwarz Pharma, Inc. v. Paddock Labs., Inc.  Specifically, Lourie said that, like in Schwarz, “when the language of both original and issued claims begins with the words ‘[a] pharmaceutical composition’, that language defines the field of the invention for purposes of determining foreseeability,” and that “PVA MBCs need only to have been known in the field of pharmaceutical compositions as of the time of Duramed’s narrowing amendment.” That was established by the Coloron PCT reference, which disclosed PVA MBCs for use in pharmaceutical compositions “as a matter of law.”

What the Duramed case should tell patentees is that asserting “unforeseeability of the equivalent” to rebut an otherwise clear instance of prosecution history estoppel (e.g., claim amendment to gain allowance) is almost certain to be a losing argument.  In fact, I’m unaware of any instance where asserting “unforeseeability of the equivalent” has been successful in rebutting prosecution history estoppel.  With regard to the second exception (known commonly as the “amendment tangential to patentability” exception), I’m aware of only one instance where it was successfully asserted in the 2010 case of Funai Electric Company, Inc. v. Daewoo Electronics Corp. authored by Judge Newman.  So patentees should now be forewarned:  whatever “flexibility” the Supreme Court may have created in Festo with these two exceptions to prosecution history estoppel being a bar to the doctrine of equivalents, it’s pretty much a mirage.

*© 2011 Eric W. Guttag


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2 comments so far.

  • [Avatar for EG]
    July 27, 2011 06:53 am

    “actually winning a suit on DOE is rarer than winning the lottery.”


    Or successfully arguing that an “on sale” bar is an “experimental use.” Like arguing “experimenta use” to rebut an “on sale” bar, arguing that the equivalent is “unforeseeable” to avoid PHE is an argument born of desperation. Thanks for the comments.

  • [Avatar for Paul F. Morgan]
    Paul F. Morgan
    July 26, 2011 08:53 pm

    Yes indeed this article nicely confirms the view that actually winning a suit on DOE is rarer than winning the lottery. Parts of KSR also do not help non-analgous-art “forseeability” arguments. The very poor odds of actually winning discourages most conceincious patent owners from bringing suit without infringement.
    However, did not failing to FULLY kill DOE have a significant unintened consequence? I.e., cannot DOE still be argued by trolls and others to confuse and resist pre-trial D.J. motions or sanctions that might othewise prevent their getting the usual defendant’s trial and discovery cost avoidance “settlements” for suits on claims that are not even broadly literally infringed?