By Kevin E. Noonan --
The doctrine of equivalents, and the extent to which prosecution history estoppel limits application of the doctrine, was perhaps the issue that prompted the Supreme Court to start its decade-long review (and, generally, reversal) of Federal Circuit precedent (in cases like eBay Inc. v. MercExchange, L.L.C., KSR Int'l Co. v. Teleflex Inc., MedImmune, Inc. v. Genentech, Inc., Microsoft Corp. v. AT&T Corp., and Quanta Computer, Inc. v. LG Electronics, Inc.). The Supreme Court and the Federal Circuit used the Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co. case to set rough contours of how these two legal doctrines interact. The Supreme Court's last word, in Festo VIII, established three grounds for rebutting a presumption of estoppel for amendments submitted during patent prosecution for reasons "substantially related to patentability." These are: 1) that the equivalent was unforeseeable, 2) that the amendment had only a tangential relation to the equivalent, or 3) that there was "some other reason" that suggested the patentee would not have reasonably been expected to describe the equivalent. The Federal Circuit, tasked with establishing the extent to which these exceptions apply, last spoke in Festo X, where the Court held that "an alternative is foreseeable if it is disclosed in the pertinent prior art in the field of the invention. In other words, an alternative is foreseeable if it is known in the field of the invention as reflected in the claim scope before amendment." Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 493 F.3d 1368, 1379 (Fed. Cir. 2007).
However, as in other areas of patent law where the Federal Circuit must labor to flesh out rather broad, general directives from the Supreme Court (such as obviousness under KSR), development in the lower courts occurs on a case-by-case basis. The latest case in which the Court assessed the scope of foreseeability for rebutting prosecution history estoppel, Duramed Pharmaceuticals, Inc. v. Paddock Laboratories, Inc., followed a trend started in Festo X and applied in several other doctrine of equivalents decisions by the Federal Circuit in the nine years since the Supreme Court established foreseeability as a basis for rebutting the presumption of prosecution history estoppel. The Court affirmed a District Court finding that the presumption of prosecution history estoppel applied to the claim limitation at issue (relating to ethyl cellulose used as a moisture barrier coating element in a pharmaceutical formulation of conjugated estrogens) because the patentee, Duramed, narrowed the scope of that claim element to response to a rejection over prior art. The Federal Circuit rejected Duramed's assertion that the alleged equivalent used by accused infringer Paddock Labs (polyvinyl alcohol) was not foreseeable, because polyvinyl alcohol was known in the pharmaceutical arts as a moisture barrier coating for pharmaceuticals, and that the failure of the art to teach this use specifically in combination with conjugated estrogens did not make its use unforeseeable.
This decision is consistent with how the Federal Circuit has consistently applied unforeseeability as a basis for rebutting the presumption of prosecution history estoppel. In Festo X, the Court held that "foreseeability does not require that the accused infringing product or process be foreseeable, nor that any equivalent exist at the time; rather foreseeability only requires that one of ordinary skill in the art would have reasonably foreseen the proposed equivalent at the pertinent time." Festo X, 493 F.3d at 1382. Further:
This criterion presents an objective inquiry, asking whether the alleged equivalent would have been unforeseeable to one of ordinary skill in the art at the time of the amendment. Usually, if the alleged equivalent represents later-developed technology (e.g., transistors in relation to vacuum tubes, or Velcro® in relation to fasteners) or technology that was not known in the relevant art, then it would not have been foreseeable. In contrast, old technology, while not always foreseeable, would more likely have been foreseeable. Indeed, if the alleged equivalent were known in the prior art in the field of the invention, it certainly should have been foreseeable at the time of the amendment. By its very nature, objective unforeseeability depends on underlying factual issues relating to, for example, the state of the art and the understanding of a hypothetical person of ordinary skill in the art at the time of the amendment. Therefore, in determining whether an alleged equivalent would have been unforeseeable, a district court may hear expert testimony and consider other extrinsic evidence relating to the relevant factual inquiries.
Festo IX, 344 F.3d at 1369. The theoretical underpinnings of this standard were enunciated by the Federal Circuit in Honeywell Int'l, Inc. v. Hamilton Sundstrand Corp., 523 F.3d 1304, 1312-13 (Fed. Cir. 2008):
The principle of foreseeability ties patent enforcement appropriately to patent acquisition. In making this connection, foreseeability reconciles the preeminent notice function of patent claims with the protective function of the doctrine of equivalents. Thus, foreseeability in this context ensures that the doctrine does not capture subject matter that the patent drafter could have foreseen during prosecution and included in the claims. The goal of the principle is to ensure that the claims continue to define patent scope in all foreseeable circumstances, while protecting patent owners against insubstantial variations from a claimed element in unforeseeable circumstances. The foreseeability principle thus relegates the doctrine of equivalents to its appropriate exceptional place in patent enforcement.
The Court specifically rejected the argument (raised again by Duramed) that the equivalent must be foreseeable for the specific use for which it is applied in the allegedly infringing article in Schwarz Pharma, Inc. v. Paddock Labs., Inc., 504 F.3d 1371 (Fed. Cir. 2007). There, the accused infringing article contained MgO as an equivalent to an alkali or alkaline earth metal carbonate in a pharmaceutical formulation of moexipil hydrochloride (and ACE inhibitor).
The Court came to the same conclusion in Glaxo Wellcome, Inc. v. Impax Laboratories, Inc., 356 F.3d 1348 (Fed. Cir. 2004), which involved sustained release formulations of bupropion hydrochloride sold by Glaxo as Wellbutrin®SR for treatment of depression and as Zyban® for smoking cessation. The limitation added by amendment was that the formulation comprised hydroxypropyl methylcellulose (HPMC, a partly O-methylated and O-(2-hydroxypropylated) cellulose), where the accused infringing article contained hydroxypropyl cellulose (HPC). The Federal Circuit affirmed the District Court's finding that "anyone skilled in the art [at the relevant time] would have known that HPC and HPMC were substantially equivalent," and that the Supreme Court required that a patent "must show that at the time of the amendment [that] one skilled in the art could not reasonably be expected to have drafted a claim that would have literally encompassed the alleged equivalent." Festo VIII, 535 U.S. at 741. "The Supreme Court ties foreseeability to whether the applicant would have been expected to know of, and thus properly claim, the proposed equivalent at the time of amendment." The "quintessential example of an unforeseeable equivalent" according to the Court, is after-arising technology, and unforeseeability as a basis for rebutting the presumption of prosecution history estoppel "compensates for the patentee's inability to claim" the unforeseeable.
In Glaxo, the Federal Circuit expressly uncoupled the existence (and hence foreseeability) of an equivalent from whether it was known to be an equivalent, citing this language from the Supreme Court's Festo VIII opinion:
The Supreme Court's passage addresses the time of amendment only and does not address the instance where the applicant could not properly claim a known equivalent because it had purposely left that known substitute out of its disclosure at the time of filing. In such an instance, the applicant should have foreseen and included the proposed equivalent in its claims at the time of filing. The Supreme Court states clearly in Festo: "The patentee, as the author of the claim language, may be expected to draft claims encompassing readily known equivalents." 535 U.S. at 740.
Viewed in this light, the result in Duramed is unremarkable, but points out once again that the Federal Circuit will seek (under the appropriate evidentiary circumstances) to use prosecution history estoppel to limit the scope of equivalents available to patentees. This is particularly important in technologies, such as the biotech and especially the pharmaceutical industries, where salts, excipients, and other components of commercially valuable formulations and dosage forms can be substituted to provide substantially the same active pharmaceutical agent in alternative forms. These alternative excipients will thus always exist in the pharmaceutical arts and thus presumptively be foreseeable at the time an estoppel-raising amendment is made. Moreover, the argument regarding unforeseeability supporting the rebuttal of prosecution history estoppel is in conflict with the assertion that the accused infringing article comprises an equivalent: the same factors (interchangeability, insubstantial differences) that support infringement under the doctrine of equivalents also support the argument that the equivalent was foreseeable. See Ranbaxy Pharms. Inc. v. Apotex, Inc., 350 F.3d 1235 (Fed. Cir. 2003). The availability of these choices suggests that claims useful and sufficient to protect pharmaceutical and biotech drugs should be pursued with the minimum of amendment, either by crafting several claims of narrow scope or including in claims only the minimum required ingredients to provide operable embodiments of the invention. The commercial and pharmaceutical "equivalence" of PVA and ethyl cellulose-containing excipients as moisture barrier agents was established by Paddock's successful incorporation of PVAs into it commercial embodiments. The legal equivalence as evidenced by the cited art suggests that the patentees could profitably have either included PVAs (and any other promising, or not so promising, moisture barrier coatings) in their specification, or avoided reciting these excipients in the claims of the '638 patent. In either case, because only hindsight is 20-20, it will remain a challenge to appropriately protect pharmaceutical and biologic drugs in view of the Federal Circuit's parsimonious application of the doctrine of equivalents.