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What Does “Stable” Mean in a Composition Claim? – Clearly Defining Claimed Parameters

August 3, 2021by Jacob Doughty

Ex parte Ratcliff, is a recent decision of the Patent Trial and Appeal Board (PTAB) addressing whether the requirement that a component of a claimed composition “remains stable in the composition” was indefinite.

In Ex parte Ratcliff, the claim at issue was directed to an oral rinse composition. The relevant claim recited:

An oral rinse composition for enhancing tooth remineralization, comprising:

stabilized chlorine dioxide that remains stable in the composition, the stabilized chlorine dioxide capable of reacting with acidic elements of oral biofilms to produce chlorine dioxide gas;

sodium fluoride; and

a pharmaceutically acceptable buffer effective at establishing an effective pH range of the composition from about 6.0 to about 7.4 for maintaining the stability of the chlorine dioxide in the composition;

wherein the stabilized chlorine dioxide and the sodium fluoride in combination are more effective at enhancing tooth remineralization and reducing tooth demineralization than either of the stabilized chlorine dioxide or the sodium fluoride alone.

In this case, the examiner took issue with the above-emphasized phrase “stabilized chlorine dioxide that remains stable in the composition.” Particularly, the examiner asserted that “… the claim does not provide a discernable boundary on what provides the functional characteristic to the stabilized chlorine dioxide (SCD),” wondering whether stabilized chlorine dioxide is stable in the composition:

… due to the addition of some other structure (such as pH modifiers, stabilizers, etc.), absence of destabilizing agents (such as stannous chloride), other features of the composition (such as specific pH ranges)… due to a sequence of steps by which it is made or by some other means, or a certain combination of these.

Applicant argued that “stability” was adequately defined in the specification as the “ability to maintain levels of the… chlorine dioxide source… within the levels specified by the present invention when the final composition is placed under…” specified storage conditions. However, the PTAB noted that the “levels specified by the present invention” were not defined in the claim or specification (or identified by applicant in its appeal briefing).

The PTAB searched the specification for further guidance and found a general disclosure of amounts of the chlorine dioxide source (0.005% w/w to 0.800% w/w) and disclosure that a reduction in the amount of stabilized chlorine dioxide after storage (0.125% w/w >> 0.04% w/w) indicated that stability was achievable. However, the PTAB found that there was insufficient guidance in the specification regarding “how much stabilized chlorine dioxide must remain in the composition after being stored under the specified conditions, in order to be stable according to the definition of stability provided in [the specification].” Thus, the PTAB affirmed the examiner, finding the claim so ambiguous that it failed to inform a skilled artisan about the scope of the claimed invention with reasonable certainty.

The PTAB reversed the only other rejection on appeal – an obviousness rejection. However, this was a pyrrhic victory. The PTAB stated that “the scope of the claimed subject matter is so uncertain that we cannot meaningfully perform the required comparison between the composition recited in [the claim] and the compositions of the cited prior art.”

Takeaway: It was apparent in this case that the PTAB was looking for a number – how much stabilized chlorine dioxide would need to remain in the composition after storing under specified conditions for the stabilized chlorine dioxide to be deemed “stable in the composition”? For claims as in this case, it can be helpful to consider how the difference between “stable” and “not stable” will be explained to a lay jury. If it will be hard to show a lay jury the line between infringing and not infringing, it may be preferable to claim the composition differently (maybe product-by-process).

In this case, both the examiner and the PTAB relied on their own judgment of how a skilled artisan would have viewed the meaning of stability. While applicant provided experimental evidence to show that certain prior art compositions did not include stabilized chlorine dioxide that remains stable, a succinct statement from a skilled artisan regarding how to determine whether stabilized chlorine dioxide “remains stable in the composition” may have framed the issue of indefiniteness in a more favorable manner.

Judges: Adams, Prats, Townsend

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PTAB Reverses Obviousness Rejection Based on Optimization of Different Property

November 20, 2020by Matthew Barnet

Patent claims often recite structural limitations in combination with one or more properties. In the chemical arts, for example, a claim might recite a copolymer comprising certain monomer components, where the copolymer has certain rheological properties (e.g., melt flow rate, die swell).

In such cases, U.S. examiners often rely on the theory of inherency to fill gaps in the prior art. If the prior art describes the claimed structural limitations, but not the claimed properties, examiners often take the position that the claimed properties would be inherent in the structure of the prior art, even though the properties are not explicitly described in the prior art (see, e.g., here and here).

Alternatively, U.S. examiners sometimes take the position that the claimed properties would result from an obvious optimization of a different property in the prior art. This issue is illustrated in the recent Patent Trial and Appeal Board (“Board”) case of Ex parte Isaka.

Claim 1 recited (in part):

A tetrafluoroethylene/hexafluoropropylene copolymer having a melt flow rate measured at 372°C of 35.0 to 45.0 g/10 minutes and a die swell of -8.0% to 5.0%…

Claim 1 also recited a detailed method by which die swell was measured.

The examiner rejected claim 1 as obvious over a combination of two references. The primary reference (“Burch”) described a tetrafluoroethylene/hexafluoropropylene copolymer having a melt flow rate overlapping the claimed range. However, Burch was silent regarding the die swell of its copolymer.

The examiner relied on a second, evidentiary reference (“Krevelen”) for the property of die swell. The examiner found that Krevelen taught a correlation between the molecular weight of a polymer and its swelling properties. The examiner found that it would have been obvious to modify the molecular weight of the copolymer in Burch to optimize the melt flow properties of the copolymer. The examiner took the position that “[i]n modifying the melt flow properties…one would also be optimizing the die swell properties, as these properties are related through the polymer weight average molecular weight.” Thus, the examiner concluded that the die swell in claim 1 would result from an obvious optimization of melt flow properties in the prior art.

The Board disagreed with the examiner. Instead, the Board agreed with the applicant that “optimizing melt flow rate and molecular weight is not equivalent to optimizing die swell properties.”

In particular, the Board found that Krevelen taught that “die swell is modified by both molecular weight and molecular weight distribution.” The Board was not convinced that modifying the molecular weight by itself (i.e., without also accounting for the molecular weight distribution) would result in optimized die swell properties reading on claim 1.

The Board concluded that the examiner “did not sufficiently explain why a person of skill in the art would have had reason to adjust molecular weight distribution or why a person of skill in the art would otherwise have reason to adjust process variables in a manner that would reach claim 1’s recited die swell of -8.0% to 5.0%.” Accordingly, the Board reversed the obviousness rejection.

Takeaway: If an examiner takes the position that a claimed property would result from an obvious optimization of a different property in the prior art, it can be helpful to argue that optimizing the property in the prior art would not necessarily optimize the claimed property. As with arguments against inherency rejections, arguments in this situation are strengthened by technical explanations, optionally supported by experimental data.

Judges: Owens, Baumeister, Range

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PTAB Reverses Examiner’s Inherency Rejection Due to Conflicting Evidence

October 30, 2020by Matthew Barnet1

U.S. patent examiners sometimes rely on the theory of inherency to fill gaps in the prior art. This usually occurs when patent claims recite structural limitations in combination with one or more properties. If the prior art describes the claimed structural limitations, but not the claimed properties, examiners often take the position that the claimed properties would be inherent in the structure of the prior art, even though the properties are not explicitly described in the prior art.

Under U.S. law, however, the mere possibility that the prior art possesses the claimed properties is insufficient to establish inherent anticipation or obviousness. Instead, to establish inherency, the examiner must provide a rationale that the claimed properties are necessarily present in the prior art.

This issue is illustrated in the recent Patent Trial and Appeal Board (“Board”) case of Ex parte Liu. The claims at issue recited:

A polymer composite composition comprising:

an eggshell component, wherein the eggshell component possesses a lipid-protein structure substantially similar to that of the eggshell from which the eggshell component is derived, and wherein the eggshell component is substantially free of eggshell inner membrane material; and

a polymer component.

The inventors discovered that an improved polymer composite could be produced by using an eggshell component possessing its original lipid-protein structure and being free of the inner membrane of the original eggshell. The original lipid-protein structure was thought to maintain the hydrophobicity of the eggshell component when dispersing the eggshell component as a powder into the polymer component.

The examiner rejected the claims as obvious over a combination of references. The primary reference (“New”) described separating pulverized eggshells from their attached membranes using airflow. A secondary reference (“Minagoshi”) described combining eggshell powders in polymeric rubber compositions. The examiner took the position that it would have been obvious to use the pulverized eggshells from New as the powder in Minagoshi, to obtain the claimed polymer composite composition.

The references did not specifically describe that the eggshell component possessed a lipid-protein structure substantially similar to that of the eggshell from which the eggshell component was derived, as recited in the claims. To fill this gap in the prior art, the examiner took the position that the eggshell powder produced in New would inherently retain the original lipid-protein structure. This position was based on New allegedly “using airflow without harsh chemicals or high temperatures” to separate the membrane from the eggshells. Since the reference was silent with respect to its processing temperature, the examiner took the position that it was performed at room temperature.

The applicant provided a declaration explaining that “[e]ggshell can be denatured at a relatively low temperature” and “temperatures above 41°C will break the interactions of many proteins and denature them.” The applicant acknowledged that New did not specifically disclose the temperature used in its process, but argued that the high-speed airflow in this process would result in a temperature above 41°C. Such a temperature would denature the eggshell, such that it would not possess the lipid-protein structure recited in the claim.

Thus, the examiner argued that New used a temperature below 41°C (resulting in a product meeting the claimed limitation), whereas the applicant argued that New used a temperature above 41°C (resulting in a product not meeting the claimed limitation).

Considering these conflicting arguments and evidence, the Board found the examiner’s inherency position untenable. The Board found that “it is uncertain what temperature New’s process suggests. The preponderance of the evidence of record, therefore, does not support a finding that New’s process inherently takes place at a temperature of less than 41°C.” The Board concluded that “[t]he evidence, therefore, also does not support a finding that New’s process necessarily results in an eggshell composition which possesses a lipid-protein structure substantially similar to that of the eggshell from which the eggshell component is derived,” as recited in the claims. Accordingly, the Board reversed the obviousness rejections.

To be clear, the Board did not find that New’s process was inherently performed at a temperature above 41°C, as applicant argued. Instead, the Board found that the evidence was inconclusive as to what temperature the process occurred. This uncertainty in temperature was the key to the Board’s decision on inherency. As the Board noted, “[i]nherency…may not be established by probabilities or possibilities. The mere fact that a certain thing may result from a given set of circumstances is not sufficient” (citing In re Robertson, 169 F.3d 743, 745 (Fed. Cir. 1999)). Even though it was possible that New’s process was performed at a temperature below 41°C, as alleged by the examiner, this possibility was insufficient to establish that the temperature inherently was below 41°C.

Takeaway: Inherency requires necessity, not merely possibility. That is, just because it might be possible for the prior art to satisfy a claimed property, that does not mean that the prior art necessarily satisfies the property. If the prior art does not necessarily satisfy the claimed property, then inherency has not been established. When there is conflicting evidence, some in support of a claimed property being present and some in support of a claimed property being absent, this conflict itself can support an argument against inherency.

Judges: Gaudette, Wilson, Range

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Inherency Requires Reference Unavoidably Teach Claimed Property

September 4, 2020by Beau Burton

On August 19, 2020, the Patent Trial and Appeal Board (“Board”) issued a decision in Ex parte Boutillier (Appeal No. 2020-000348) reversing an Examiner’s obviousness rejection for failing to establish that the prior art inherently taught a claimed property.

The independent claim in Boutillier required a composition that included an elastomeric phase formed of a block copolymer, where the block copolymer had “a water solubility of less than 0.5 g/l.”

The prior art cited by the Examiner disclosed water soluble block copolymers that could be formed from the same monomers and in the same proportions recited in the Applicant’s dependent claims (e.g., acrylic and/or methacrylic monomers). Although the prior art did not disclose the water solubility of the block copolymer, the Examiner reasoned that “[the] instantly claimed water solubility can be made from the disclosure of [the prior art]” because the copolymer of the prior art “can include the same monomers as instantly claimed, within the same weight ranges as instantly claimed.”

The Applicant disagreed with the Examiner’s reasoning because the block copolymers of the prior art were characterized as being water soluble, and thus, would not be expected to have a water solubility less than 0.5 g/l.

The Board sided with the Applicant. The Board found that even though it was undisputed that the prior art taught block copolymers that could be prepared from the same monomers claimed by the Applicant, the prior art expressly taught its block copolymers were water soluble. The mere fact that it might be possible to prepare a block copolymer with a water solubility of less than 0.5 g/l with the monomers disclosed in the prior art was insufficient to establish the inherency of this feature.

The Board emphasized that the “very essence of inherency is that one of ordinary skill in the art would recognize that a reference unavoidably teaches the property in question.” Agilent Technologies, Inc. v. Affymetrix, Inc., 567 F.3d 1366, 1383 (Fed. Cir. 2009). And, in this case, the water solubility of less than 0.5 g/l was not “unavoidable or the natural result following [the prior art’s] teaching.”

Takeaway: Examiners often rely on the rationale that “if the prior art teaches the identical chemical structure, the properties applicant discloses and/or claims are necessarily present.” In re Spada 911 F.2d 705 (Fed. Cir. 1990). However, this rationale breaks down in two situations. The first is where there is a broader teaching in the prior art, as in this case, that suggests the property would not necessarily be present despite similarities in the chemical structures. The second is where there is a generic disclosure in the prior art that encompasses–but does not specifically teach–the identical structure claimed. In this situation, a presumption of inherency can be rebutted by showing that one or more species falling within the generic disclosure do not exhibit the claimed property.

Judges: E. Grimes, F. Prats, L. Ren

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