prosecution history estoppel : CAFC Alert

Prosecution history estoppel applies to narrowing amendment for a purpose, but not for all purposes

| September 25, 2020

Bio-Rad Laboratories, Inc., Et Al. v. 10X Genomics Inc.

August 3, 2020

Newman, O’Malley (Opinion author), and Taranto


The Federal Circuit held that 10X infringes Bio-Rad’s ‘083 patent under the doctrine of equivalents because a tangential exception to the prosecution history estoppel applies in this case.


Bio-Rad Laboratories, Inc. and the University of Chicago (collectively, “Bio-Rad”) accused 10X Genomics Inc. (“10X”) of infringing three patents: U.S. Patent Nos. 8,888,083 (“083 patent”); 8,304,193 (“193 patent”); and 8,329,407 (“407 patent”). The United States District Court for the District of Delaware held that 10X willfully infringed all three patents and awarded damages in an amount of $23,930,716.

The patents-in-suit are directed to systems and methods for forming microscopic droplets (also called “plugs”) of fluids to perform biochemical reactions. Claim 1 of the ‘083 patent, as below, is representative:

A microfluidic system comprising:

a non-fluorinated microchannel;

a carrier fluid comprising a fluorinated oil and a fluorinated surfactant comprising a hydrophilic head group in the microchannel;

at least one plug comprising an aqueous plug-fluid in the microchannel and substantially encased by the carrier-fluid, wherein the fluorinated surfactant is present at a concentration such that surface tension at the plug-fluid/microchannel wall interface is higher than surface tension at the plug-fluid/carrier fluid interface.

During prosecution, the inventors amended the claims, as underlined above, to distinguish from a prior art, U.S. Patent No. 7,294,503 (“Quake”). Quake disclosed microchannels formed or coated with Teflon (a fluorinated polymer) or other fluorinated oils. Furthermore, the inventors argued that their invention attempts to prevent droplets from sticking to the walls of microchannels and requires that the “surfactant should be chemically similar to the carrier fluid and chemically different from the channel walls.” That is, the non-fluorinated microchannels and the fluorinated surfactant are required not to react with each other. This is the purpose of the amendment. In contrast, Quake did not teach that microchannels and carriers fluids were chemically distinct, and the fluorinated microchannels and surfactants could, therefore, react with each other.

After the litigation was filed, 10X modified its products to add 0.02% Kynar-a non-reactive amount of a fluorine-containing resin-to its microchannels. 10X concedes that the addition of this amount of Kynar is irrelevant to the functioning of its products. In the District Court, the jury found that 10X’s accused products, as modified, do not literally satisfy the “non-fluorinated microchannels” limitation, but meet the limitation under the doctrine of equivalents. On appeal, among other issues, 10X argued that prosecution history estoppel and claim vitiation barred Bio-Rad’s theory of equivalence. The District Court held that prosecution history estoppel does not apply in this case because the amendment at issue was only tangentially related to the accused equivalent.

On appeal, 10X continued to argue that prosecution history estoppel applies because the inventors’ amendment narrowed the claims to recite a “non-fluorinated microchannel” to overcome Quake, which taught “fluorinated” microchannels. As such, the inventors surrendered the right to expand their monopoly to cover microchannels containing fluorine, “for whatever purpose.” In response, Bio-Rad counter argued that the reason for narrowing the claims was peripheral, or not directly relevant to the alleged equivalent. Bio-Rad contends that the patentees amended the claims to make clear that the carrier fluid and the microchannel wall should be chemically distinct, which bears no more than a tangential relation to the alleged equivalent-microchannel walls containing a nominal amount of fluorine that is not chemically distinct from the carrier fluid. The Federal Circuit agreed with Bio-Rad, and reasoned that inventors surrendered microchannels coated with fluorine that reacted with carrier fluids, not those containing de minimis amounts of fluorine that have no effect on how the microchannel functions in the system. The narrowing amendment can only be said to have a tangential relation to the equivalent at issue-negligibly fluorinated microchannels, or microchannels with non-fluorinated properties. That is, the inventors surrendered microchannels coated with fluorine for a purpose, but not for all purposes.

Take away

  1. During prosecution, inventors should also explain in detail the purpose of the amendment of claims in order to narrow the scope surrendered by the amendment.

One correct way of reciting a Markush group in the claim

| January 24, 2020

Amgen Inc. v. Amneal Pharmaceuticals LLC

January 7, 2020

Lourie (Opinion author), Newman, and Taranto


The Federal Circuit reversed the district court’s claim construction of the Markush groups as being closed to unrecited elements because the claim recites “comprising” as the transitional phrase and “at least one” in front of each of the Markush groups. Furthermore, the Federal Circuit affirmed the district court’s holding of noninfringement under the doctrine of equivalents by one of the Defendants’ products due to prosecution history estoppel.


Amneal, Piramal, and Zydus each filed an Abbreviated New Drug Application (ANDA), seeking approval of a generic version of Sensipar®, a formulation of cinacalcet hydrochloride used to treat secondary hyperparathyroidism in adult patients with chronic kidney disease who are on dialysis and to treat hypercalcemia in patients with parathyroid cancer and primary and secondary hyperparathyroidism. Amgen holds the approved New Drug Application for Sensipar®, and sued them for infringing U.S. Patent No. 9,375,405 (the ‘405 patent).

The ‘405 patent is directed to a rapid dissolution formulation of cinacalcet. Claim 1 of the ‘405 patent is as follows:

A pharmaceutical composition comprising:

(a) from about 10% to about 40% by weight of cinacalcet HCl in an amount of from about 20 mg to about 100 mg;

(b) from about 45% to about 85% by weight of a diluent selected from the group consisting of microcrystalline cellulose, starch, dicalcium phosphate, lactose, sorbitol, mannitol, sucrose, methyl dextrins, and mixtures thereof,

(c) from about 1% to about 5% by weight of at least one binder selected from the group consisting of povidone, hydroxypropyl methylcellulose, hydroxypropyl cellulose, sodium carboxymethylcellulose, and mixtures thereof; and

(d) from about 1% to 10% by weight of at least one disintegrant selected from the group consisting of crospovid[o]ne, sodium starch glycolate, croscarmellose sodium, and mixtures thereof,

wherein the percentage by weight is relative to the total weight of the composition, and wherein the composition is for the treatment of at least one of hyperparathyroidism, hyperphosphonia, hypercalcemia, and elevated calcium phosphorus product.

The ‘405 patent issued from U.S. Patent Application 12/942,646 (the ‘646 application). The original ‘646 application contained only one claim, which recited a “pharmaceutical composition comprising an effective dosage amount of a calcium receptor-active compound and at least one pharmaceutically acceptable excipient, wherein” the composition achieved a specific dissolution profile. Later, Amgen filed a Preliminary Amendment, which cancelled claim 1 and added new claims 2-24. The newly filed claim 2, which ultimately issued as claim 1, is as follows:

A pharmaceutical composition comprising:

(a) from about 10% to about 40% by weight of cinacalcet HCl;

(b) from about 45% to about 85% by weight of a diluent selected from the group consisting of microcrystalline cellulose, starch, dicalcium phosphate, lactose, sorbitol, mannitol, sucrose, methyl dextrins, and mixtures thereof,

(c) from about 1% to about 5% by weight of at least one binder; and

(d) from about 1% to 10% by weight of at least one disintegrant,

wherein the percentage by weight is relative to the total weight of the composition.

The Examiner rejected the new claims. Then, Amgen filed an amendment of the independent claim 2, reciting “from about 10% to about 40% by weight of cinacalcet HCl in an amount of from about 20 mg to about 100mg.” Then, Amgen conducted a phone interview with the Examiner. During the interview, the Examiner proposed an Examiner’s Amendment of the independent claim 2, and Amgen accepted the Examiner’s Amendment. Specifically, the Examiner’s Amendment revised the binder and the disintegrant limitations into their current, Markush group format. Then, the claims are allowed. After the Notice of Allowance was issued, Amgen filed a number of RCE Requests with new IDS submission. In one of the RCE Requests, with regard to the previous Examiner’s Amendments, Amgen remarked that “[t]hese amendments have not been made in response to a prior art rejection but rather to place the claims in proper format and to better define the claimed subject matter, including equivalents.” The Examiner issued a Notice of Allowance after each RCE Request.

In the district court proceeding, one key issue is the construction of the binder and disintegrant Markush groups. The district court held that the Markush groups for the binder and disintegrant elements are closed to unrecited binders and disintegrants, relying on Multilayer Stretch Cling Film Holdings, Inc. v. Berry Plastics Corp., 831 F.3d 1350 (Fed. Cir. 2016). Furthermore, the district court held that Amneal does not infringe the ‘405 patent because Amneal uses Opadry Clear YS-1-7006 as the binder, a product that contains PEG 400 and PEG 8000 in addition to hydroxypropyl methylcellulose, which is a listed binder in claim 2. Furthermore, the district court held that Piramal does not infringe the ‘405 patent under the doctrine of equivalents because prosecution history estoppel barred Amgen’s argument that the cold-water soluble fraction of the preglatinized starch used by Piramal is equivalent to providone, a listed binder in claim 2.

On appeal, first, the Federal Circuit reversed the district court’s claim construction regarding the binder and disintegrant Markush groups. Specifically, contrary to the district court’s interpretation, because claim 1 uses “comprising” as the transitional phrase and “at least one” in front of each Markush group, the binder and disintegrant Markush groups do not preclude other binders and disintegrants in the claimed composition. Without more, such language is satisfied when an accused product contains a component that is from the Markush group and that meets the limitation’s other requirements such as concentration requirement for the component. Furthermore, the Federal Circuit held that Opadry used as a binder by Amneal contains HPMC, which is a listed binder in claim 1. Thus, irrespective of whether other components such as PEG are present, provided that Amneal’s formulation contains from about 1 to about 5% HPMC, the formulation literally infringes. Accordingly, the Federal Circuit vacates and remands those findings by the district court.

Next, the Federal Circuit held that Amgen’s doctrine of equivalents argument is barred by prosecution history estoppel. During the prosecution, Amgen accepted the Examiner’s Amendment that revised the claim’s disintegrant and binder limitations to be in Markush group format. Such an amendment narrows the scope of the claim, and Amgen failed to carry its burden to demonstrate that the Examiner’s Amendment was made for a reason unrelated to patentability. The Amgen’s statement in the later RCE Request was made over eight months after the Examiner’s Amendment was accepted, and accordingly does not provide any insight on the reasons for the Examiner’s Amendment. Furthermore, the tangential exception to prosecution history estoppel does not apply here because the use of pregelatinized starch as a binder is taught in the cited prior art. An amendment made to avoid prior art that contains the equivalent in question is not tangential.

Accordingly, the Federal Circuit vacated and remanded the district court’s judgment that Amneal does not infringe the ‘405 patent, and affirmed the district court’s judgment that Piramal does not infringe the ‘405 patent.

Take away

  1. The claims should recite “comprising” as the transitional phrase and “at least one” in front of the Markush groups to avoid being constructed to be closed to unrecited elements in the Markush groups.
  2. The original specification should contain a complete set of claims instead of one claim because later amendments may inevitably invoke prosecution history estoppel, which would bar most of the doctrine of equivalents arguments.
  3. The patent drafter should be mindful of an independent claim with an overly broad scope. Any later amendments during the patent prosecution may invoke prosecution history estoppel. Accordingly, the applicants have the risk of losing any protection afforded by patent infringement under the doctrine of equivalents.

Presenting multiple arguments in prosecution risks prosecution history estoppel on each of them

| November 8, 2019

Amgen Inc. v. Coherus BioSciences Inc.

July 29, 2019

Before Reyna, Hughes, and Stoll. Opinion by Stoll.


The CAFC affirmed a district court decision holding that Amgen had failed to state a claim and dismissed Amgen’s suit against Coherus for patent infringement under the doctrine of equivalents, in view of Amgen’s clear and unmistakable disclaimer of claim scope during prosecution.


Amgen Inc. and Amgen Manufacturing Ltd. (“Amgen”) sued Coherus BioSciences Inc. for infringement of U.S. Patent No. 8,273,707 (the ‘707 patent). The patent relates to methods of purifying proteins using hydrophobic interaction chromatography (“HIC”), in which a buffered salt solution containing the desired protein is poured into a HIC column and the proteins are bound to a column matrix while the impurities are washed out. However, only a limited amount of protein can bind to the matrix. If too much protein is loaded on the column, some of the protein will be lost to the solution phase before elution.

Conventionally, a higher salt concentration in a buffer solution is provided to increase the dynamic capacity of the HIC column, but the higher salt concentration causes protein instability. Amgen’s ‘707 patent discloses a process that increases the dynamic capacity of a HIC column by providing combinations of salts instead of using a single salt.

According to the ‘707 patent, any one of the three combinations of salts – citrate and sulfate, citrate and acetate, or sulfate and acetate – allows for a decreased concentration of at least one of the salts to achieve a greater dynamic capacity without compromising the quality of the protein separation.

During prosecution, the Examiner rejected the claims as being obvious in view of U.S. Patent No. 5,231,178 (“Holtz”). In reply to the Examiner’s rejection, Amgen argued that:

(1) The pending claims recite a particular combination of salts. No combinations of salts are taught nor suggested in Holtz;

(2) No particular combinations of salts recited in the pending claims are taught or suggested in Holtz; and

(3) Holtz does not teach dynamic capacity at all.

Amgen also attached a declaration from the inventor. The declaration stated that the use of the three salt combinations leads to substantial increases in the dynamic capacity of a HIC column and “[use] of this particular combination of salts greatly improves the cost-effectiveness of commercial manufacturing by reducing the number of cycles required for each harvest and reducing the processing time for each harvest.”

The Examiner again rejected Amgen’s argument and took the position that the prior art does disclose salts used in a method of purification and that adjustment of conditions was within the skill of an ordinary artisan.  This time, in response to the Examiner’s position, Amgen replied that Holtz does not disclose any combination of salts and does not mention the dynamic capacity of a HIC column. In particular, Amgen stated that it was a “lengthy development path” when choosing a working salt combination and that merely adding a second salt would not have been expected to result in the invention. The Examiner allowed the claims.

In 2016, Coherus sought FDA approval to market a biosimilar version of Amgen’s pegfilgrastim product. In 2017, Amgen sued Coherus for infringing the ‘707 patent under the doctrine of equivalents because Coherus’s process did not match any of the three explicitly recited salt combinations in the ‘707 patent. Coherus moved to dismiss Amgen’s complaint for failure to state a claim.

The district court agreed to dismiss the complaint. The district court noted that during prosecution, Amgen had distinguished Holtz by repeatedly arguing that Holtz did not disclose “one of the particular, recited combinations of salts” in the two responses and in the declaration. The district court held that “[t]he prosecution history, namely, the patentee’s correspondence in response to two office actions and a final rejection, shows a clear and unmistakable surrender of claim scope by the patentee.”  In addition, the district court held that “by disclosing but not claiming the salt combination used by Coherus, Amgen had dedicated that particular combination to the public.”

Amgen appealed.

The CAFC affirmed the district Court’s dismissal and found that the “prosecution history estoppel has barred Amgen from succeeding on its infringement claim under the doctrine of equivalents.”

In the appeal, Amgen argued that it only had distinguished Holtz by stating that Holtz does not disclose increasing any dynamic capacity or mention any salt combination. Amgen also argued that the prosecution history should not apply here because the last response filed prior to allowance did not make the argument that Holtz failed to disclose the particular salt combinations.

Regarding Amgen’s first point – that during prosecution, only dynamic capacity had been used to distinguish Holtz – the CAFC noted the three grounds on which Amgen has relied for distinguishing Holtz, and the fact that Amgen had quoted the declaration in support of the particular combination of salts recited in the claims.  The CAFC explained that “separate arguments create separate estoppels as long as the prior art was not distinguished based on the combination of these various grounds.”

The CAFC also disagreed with Amgen’s second point (that prosecution history estoppel should not apply because of their last response), commenting that “there is no requirement that argument-based estoppel apply only to arguments made in the most recent submission before allowance…  We see nothing in Amgen’s final submission that disavows the clear and unmistakable surrender of unclaimed salt combinations made in Amgen’s response.”

The CAFC held that the prosecution history estoppel applied and affirmed the District Court’s order dismissing Amgen’s complaint for failure to state a claim. The CAFC did not discuss whether Amgen dedicated unclaimed salt combinations to the public.


  • Prosecution history estoppel can be triggered, not only by narrowing amendments, but also by arguments, even without any amendments.
  • Presenting multiple arguments does not eliminate the risk of triggering estoppel for each of them.
  • When writing an argument, avoid using expressions that are not recited in the claims (when discussing the claimed invention) or the cited documents (when discussing the state of the art).

Be Mindful that the Potential Reach of Claimed Components under the Doctrine of Equivalents Can Be Affected by Amendments to Claimed Sub-Components.

| October 9, 2014

EMD Millipore Corporation v. Allpure Technologies, Inc. (Precedential Opinion).

September 29, 2014

Panel:  Prost, O’Malley and Hughes.  Opinion by Prost.


EMD Millipore Corporation (Millipore) appeals the District of Massachusetts decision that the accused infringer, Allpure Technologies, Inc. (Allpure) does not infringe its U.S. Patent No. 6,032,543 entitled a Device for Introduction and/or Withdrawal of a Medium into/from a Container, either literally or under the doctrine of equivalents.   The Federal Circuit affirmed that there was no literal infringement because the claims required a removable transfer member having a two part seal connected after removal, while the Allpure device had two parts of a seal separated after disassembly.   In addition, the Federal Circuit held that Allpure did not infringe under the doctrine of equivalents due to prosecution history estoppel  based on narrowing amendments limiting the transfer member to such a two part seal, along with a lack of any argument that the reasons for such amendments was not a substantial one related to patentability.

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In case of first impression, the CAFC determines that the principles of prosecution history estoppel apply to design patents.

| January 31, 2014

Pacific Coast Marine v. Malibu Boats, LLC

Decided January 8, 2014

Before Dyk, Mayer, and Chen. Opinion by Dyk.


Bach’s original design patent application included multiple embodiments of a marine windshield.  The Examiner issued a restriction requirement, in response to which Bach elected the first embodiment, canceled the other four, and filed a divisional for the third embodiment only.  After the patent issued, Bach assigned it to Pacific Coast, which sued Malibu Boats for infringement.  The Malibu Boats windshield differed slightly from the patented embodiment, as well as the non-elected embodiments.  The district court granted Malibu Boats’ motion for partial summary judgment of non-infringement on the grounds of prosecution history estoppel, finding that “that, during prosecution, the applicant had surrendered the designs reflected in the canceled figures and amended the claim ‘in order to obtain the patent.’”  The CAFC reversed, holding that although “there was a surrender of claim scope during prosecution,” the accused design was not “within the scope of the surrender.”

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Don’t Keep Limitations Not Needed To Distinguish the Prior Art

| November 6, 2013

Integrated Technology Corporation v. Rudolph Technologies, Inc.

November 4, 2013

Moore (author), Rader, and Clevenger


The CAFC reversed the denial of Rudolph’s motion for JMOL that its accused no-touch products do not infringe under the doctrine of equivalents.  The CAFC found that prosecution history estoppel (preventing ITC from recapturing through the doctrine of equivalents the subject matter that ITC surrendered during prosecution) presumptively applies, and that ITC failed to rebut the presumption because it failed to establish one of three exceptions by a preponderance of the evidence.

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Disavowal of Claim Terms is a Stringent Hurdle to Overcome, which must be “Clear and Unmistakable” Disavowal to Limit the Scope of Claims

| August 14, 2013

Plantronics, Inc. v. Aliph, inc. and Aliphcom, Inc.

July 31, 2013

Panel:  Rader, O’Malley and Wallach.  Opinion by Wallach.


This is a patent infringement suit by Plantronics against Aliph.  Plantronics is owner of US Patent 5,712,453 (‘453 patent) entitled, “Concha Headset Stabilizer.”  This is a concha-type headset to anchor in a user’s ear for use in a telephone receiver.

The district court granted-in-part summary judgment for Aliph, for noninfringement and invalidity.  After appeal, the Federal Circuit reversed-in-part, vacated in part and remanded for further proceedings.  More specifically, the Federal Circuit reversed the summary judgment of noninfringement and invalidity.  The discussion below will focus on the issue of noninfringement.

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Clear and Unmistakeable Evidence of a Disclaimer Found in Response to Enablement Rejection

| April 24, 2013

Biogen Idec, Inc., et al. v. GlaxoSmithKline LLC, et al.

April 16, 2013

Panel: Dyk, Plager, Reyna.  Opinion by Reyna.  Dissent by Plager.


During prosecution of the patent, applicants responded to the examiner’s enablement rejection, wherein they failed to challenge the examiner’s understanding of the crucial terms, and limited their invention to what the examiner believed their specification enabled.  The CAFC affirmed the district court’s narrow claim interpretation of the term “anti-CD20 antibody” based on prosecution history disclaimer.

実施可能要件を満たしていないとして発せられた拒絶通知に対して、出願人は、審査官の理解に対して反論することなく、明細書により実施可能であると審査官が判断したものに発明を限定するような主張を行った。よって、「anti-CD20 antibody」という用語について、狭いクレーム解釈を容認した地裁の判断は誤りでなかったとCAFCは判示した。

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Divided Claim Construction Leads to Reversal of Jury Verdict Against Alleged Infringer

| April 17, 2013

Saffran v. Johnson & Johnson

April 4, 2013

Panel: Lourie, Moore, and O’Malley.  Opinion by Lourie. Concurrence Opinions by Moore and O’Malley.


The Federal Circuit reversed a $482 million jury verdict against Cordis, a member of the Johnson & Johnson family. The reversal came as a result of the Federal Circuit’s significant narrowing of the district court’s construction of two key claim limitations. One claim term was narrowed because the Federal Circuit found that the patentee’s arguments made during prosecution of the asserted patent, for the purpose of distinguishing over cited prior art, amounted to prosecution disclaimer. Meanwhile, a structure identified in the specification by the patentee as the corresponding structure to a means-plus-function limitation was disregarded as such, because the specification failed to link the identified structure to the recited function with sufficient specificity.

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Prosecution Argument Bars Later Recapture Through Broadening Reissue

| August 29, 2012

Greenliant Systems, Inc. v. Xicor LLC

August 22, 2012

Panel:  Linn, Plager and Dyk.  Opinion by Dyk


Xicor obtained a patent claiming a semiconductor device with a tunneling layer formed by low pressure chemical vapor (CVD) deposition using tetraethylorthosilicate (TEOS).   Xicor sought and obtained reissue of the patent with device claims that did not recite the use of TEOS.   Subsequently, Greenliant sued Xicor for declaratory judgment of invalidity of the reissue claims based on recapture rule, which prohibits recapture via reissue of subject matter surrendered in order to overcome prior art during prosecution of the original patent.  The District Court held the reissue claims invalid, and the Federal Circuit affirms.  Xicor had repeatedly argued during prosecution of the original patent that the product-by-process limitation of using TEOS imparted structural limitations to the final product.  This is sufficient for the recapture rule to apply, even if Xicor now recognizes that the structure of the tunneling layer does not actually depend on the material used for the CVD process, but on deposition conditions such as temperature and pressure.

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