Noted with Interest: Breaking the Chain: Section 112-Based Priority Arguments

Breaking the Chain: Section 112-Based Priority Arguments

An inter partes review (IPR) is a legal process in the United States that allows any party to challenge the validity of an issued patent before the United States Patent and Trademark Office (USPTO).  In an IPR, a patent challenger is allowed only to set forth invalidity arguments rooted in 35 U.S.C. § 102 (anticipation) and/or 35 U.S.C. § 103 (obviousness).  However, in recent years, patent challengers have successfully used 35 U.S.C. § 112 (written description or enablement) in their IPR petitions to prevent a patent from claiming the benefit of the filing date of earlier parent applications or patents, and then using those very same parents or other intervening art as the bases for a challenger’s Section 102 or Section 103 invalidity grounds.  If factually feasible, the use of 35 U.S.C. § 112 to break the chain of priority can be another tool a challenger may use as part of its IPR strategy.

1. Background
2. Inter Partes Review

An IPR is an administrative trial procedure for challenging the validity of a U.S. patent before the Patent Trial & Appeal Board (PTAB) of the USPTO.  Any person who is not the owner of a patent can file an IPR petition against an issued U.S. patent.  This person is often referred to as the petitioner or patent challenger.  In contrast to district court patent litigations, which can involve a wide range of substantive issues, including, for example, infringement, enforceability (e.g., inequitable conduct), other equitable defenses (e.g., unclean hands, laches), damages, injunctions and more, IPR petitioners are only permitted to set forth invalidity challenges (or grounds) based on anticipation under 35 U.S.C. § 102 and/or obviousness under 35 U.S.C. § 103.  As a result, a petitioner may only use prior art references such as other patents or printed publications to challenge the patent that is the subject of the IPR petition.  Notably absent from the IPR process is the ability to challenge a patent under 35 U.S.C. § 112.  As discussed herein, however, this statutory ground still has an important role to play.

After a petition is filed with the USPTO, a patent owner may file a preliminary response to the petition.  The PTAB then determines whether there is a reasonable likelihood that the petitioner would prevail with respect to at least one claim challenged.  If the PTAB determines there is a reasonable likelihood, then it institutes a trial.  A final determination by the PTAB is typically issued within one year from the institution date.  Like district court judgments in patent cases, IPRs may be appealed to the U.S. Court of Appeals for the Federal Circuit.

2. Priority Date: Breaking the Chain

A key consideration in patent validity, both in district courts and at the PTAB, is the determination of what qualifies as prior art for a challenged patent.  In order to determine which references will qualify, it is necessary first to determine the “priority date” of the challenged patent—that is, the earliest filing date in a family of patent applications.  It is generally most desirable for a patent owner to claim priority to the earliest possible filing date in order to limit the scope of references that can be used to challenge its patent.

For a patent owner to claim entitlement to an earlier priority date based on an earlier-filed application, several requirements must generally be met, including that the earlier-filed application discloses the invention claimed in the later-filed application sufficient to satisfy the written description and enablement requirements of 35 U.S.C. § 112.  See 35 U.S.C. § 120; In re NTP, Inc., 654 F.3d 1268, 1277 (Fed. Cir. 2011); see also 35 U.S.C. § 119(e).  Priority is typically determined on a claim-by-claim basis.  When a link in the chain of priority fails, i.e., when any of the priority requirements are not satisfied for each of the applications leading to the challenged patent, the challenged patent is unable to claim priority to the earlier parent application.  The later priority date expands the pool of possible prior art that can be used as a ground in a validity challenge.  A patent challenger could even assert as invalidating prior art patents and/or patent publications stemming from the very same parent applications that the challenged patent claimed priority to.

3. 35 U.S.C. §112—Written Description and Enablement

Section 112(a) provides two separate avenues to attack a claim of priority: inadequate written description and lack of enablement.  To gain the benefit of the filing date of an earlier application, each application in the chain leading back to the earlier application must comply with the written description requirement.  See 35 U.S.C. § 120; Arthrex, Inc. v. Smith & Nephew, Inc., 35 F.4th 1328, 1343 (Fed. Cir. 2022).  In other words, the disclosure of each application relied upon for priority must reasonably convey to those skilled in the art that the inventor had possession of the claimed subject matter as of the filing date sought.  Id.; see also Tronzo v. Biomet, Inc., 950 F. Supp. 1149, 1154-55 (S.D. Fla. 1996), aff'd in part, 156 F.3d 1154 (Fed. Cir. 1998).  And earlier applications satisfy the enablement requirement only if one skilled in the art, after reading their disclosures, could practice the invention (make and use the full scope of the invention) claimed in the later-filed patent without undue experimentation.  See Genentech, Inc. v. Novo Nordisk, A/S, 108 F.3d 1361, 1365 (Fed. Cir. 1997).

2. Successful Use of Priority Chain-Breaking

In recent years, patent challengers have been successful in invalidating challenged patents before the PTAB by breaking the chain of priority for lack of Section 112 support and using parent patents or publications as invalidating prior art.  And the Federal Circuit has affirmed such challenges.  See, e.g., Indivior UK Ltd. v. Dr. Reddy's Lab’ys S.A., 18 F.4th 1323, 1330 (Fed. Cir. 2021); Arthrex, Inc. v. Smith & Nephew, Inc., 35 F.4th 1328 (Fed. Cir. 2022); Reckitt Benckiser v. Ansell Healthcare, IPR2017-00063 Paper 38 and IPR2017-00066 Paper 35.

1. Parent Patents as Prior Art

If a patent (whether a continuation or continuation in part) is unable to claim priority back to an earlier filed application in the family, then a patent challenger may use intervening parent patents or patent publications as prior art to invalidate the child patent.  Although breaking priority through lack of enablement is possible, there are more examples in the case law of breaking priority because of insufficient written description.

This strategy has been used successfully in IPRs and has been affirmed by the Federal Circuit.  In Indivior UK Ltd. v. Dr. Reddy's Labys S.A., the ’454 patent at issue issued from a series of continuation applications from the parent ’571 application.  18 F.4th 1323, 1325 (Fed. Cir. 2021).  In its IPR petition, Dr. Reddy’s alleged that the claims of the ’454 patent lacked written description support in the ’571 application, and hence were not entitled to the benefit of its filing date.  Id.  Dr. Reddy’s then argued that, without the benefit of the earlier priority date, the asserted claims were anticipated by the ’571 application publication.  Id.  The claims at issue in Indivior related to an orally dissolvable film for delivery of therapeutic agents, and listed ranges of weight percentages (and in one instance not discussed here, a specific weight percent of polymer.  Id.  Regarding the range claims, the PTAB found that the claims lacked written description support in the ’571 application.  Id.  Accordingly, the PTAB held that these claims were anticipated by the parent ’571 application publication.  Id.  The Federal Circuit affirmed the PTAB’s decision.  Id. at 1330. 

Even as recently as last year, the Federal Circuit in Arthrex, Inc. v. Smith & Nephew, Inc. upheld the PTAB’s holding that a patent was invalid based on the publication of a parent application as a result of lack of written description in a parent priority application.  35 F.4th 1328 (Fed. Cir. 2022).  In this case, the ’907 patent at issue claimed the benefit of priority to the earlier parent application through a series of continuation, continuation-in-part (CIP), and divisional applications, including the relevant ’707 application.  Id. at 1342.  The Court, however, found that the intervening ’707 application lacked written description support of an element of the invention claimed in the patent at issue.  As a result, the chain of priority for the asserted patent was broken and the PTAB concluded that the patent at issue was not entitled to an earlier priority date.  Id. at 1343-44.  The PTAB thus held, and the Federal Circuit upheld, that a parent application publication was prior art to the patent at issue and anticipated the claimed invention.  Id.

This strategy has also been used successfully in district court litigations, and again, has been affirmed by the Federal Circuit.  For example, in Tronzo v. Biomet, Inc., the Federal Circuit reversed a district court’s judgment that two claims were not invalid, finding that the claims at issue were not entitled to the filing date of the parent application and were therefore anticipated by intervening prior art, including Tronzo's British application, which was the counterpart to the U.S. application that yielded the '589 patent.  156 F.3d 1154, 1155-58 (Fed. Cir. 1998).  Similarly, in Zenon Envtl., Inc. v. United States Filter Corp., the Federal Circuit reversed the district court’s holding that the ’319 patent at issue was not invalid because it found that the patent at issue was not entitled to the earlier filing date of the grandparent ’373 patent, and instead was anticipated by the same.  506 F.3d 1370, 1378 (Fed. Cir. 2007).  The Federal Circuit found the intervening applications in the chain leading back to the ’373 patent at issue did not comply with the written description requirement and “[t]hus, the chain of continuity was broken.”  Id. at 1381. As such, the Federal Circuit held that the patent at issue was not entitled to the earlier priority date and was therefore anticipated by the ’373 patent.  Id. at 1382.

2. CIPs and Continuations

The possibility of priority chain-breaking arguments may be heightened where the patent at issue is, or has descended from, a CIP application.  In this situation, a challenger may draw an inference that the material in the patent at issue cannot be found in a single source.  This is particularly compelling where any claims of the patent at issue recite subject matter from more than one patent family.  The Federal Circuit has held that applicants must satisfy Section 112 requirements in a single parent application in order to claim the benefit of an earlier filing date for individual claims.  Studiengesellschaft Kohle, M.B.H. v. Shell Oil Co., 112 F.3d 1561 (Fed. Cir. 1997) (affirming district court’s holding that Section 120 does not permit the combination of two earlier disclosures to acquire an earlier filing date).  As discussed above, priority is determined on a claim-by-claim basis.  Thus, in such a situation, each claim must be analyzed individually to determine whether it could have been added to either of the two priority applications without introducing new matter. 

However, priority chain-breaking is not limited to CIPs.  Breaking priority is also possible in continuation applications, typically where a nonprovisional application discloses new matter that was not included in the provisional application.  For example, in Purdue Pharma L.P. v. Iancu, the Federal Circuit affirmed the PTAB’s finding that the ’376 patent at issue was not entitled to claim priority to its related provisional application, and that the claims were therefore obvious over an intervening reference that qualified as prior art as a result of the later priority date.  767 Fed. Appx 918 (Fed. Cir. 2019); see also discussion of Indivior, supra.

3. Looking Ahead

Patentees and challengers alike should consider priority chain-breaking arguments based on Section 112 priority arguments when evaluating strategy for a patent case, particularly in the context of IPRs.  A petitioner may attempt to invalidate the patent at issue using Section 112 bases to break the chain of priority, and then use intervening prior art, including patents that have published or issued earlier from the same family, as Section 102 or Section 103 prior art against the challenged patent claims.  As seen above, there have been several cases recently where this was successfully done.

In the IPR context, this strategy could be useful to patent challengers.  Given the complexity of most invalidity arguments, arguments concerning breaking priority may have a higher likelihood of success as part of an IPR proceeding based on the aforementioned precedent. 

Section 112 also offers an alternative priority chain-breaking invalidity argument in district court actions.  For the same claims, a petitioner can argue as independent challenges that (1) the claims are invalid for lack of written description support under Section 112; and (2) the claims are not entitled to priority to the earlier applications because they lack written description support in the earlier application, and without the benefit of the priority claim the claims are anticipated by the parent patents and/or publications.

Both IPRs and district court litigations also provide opportunities to raise other prior art-based challenges.  A petitioner or litigant could, for example, also assert Section 103 grounds in the same action.  However, this strategy creates a specific tension: by arguing there is no support for the claims of an asserted patent in a single parent application, assuming challengers are successful in breaking priority, they could become limited to Section 103 obviousness invalidity arguments with respect to parent publications or patents.  In other words, by arguing it is necessary to combine disclosures from two applications to satisfy the written description requirement for certain claims of the asserted patents, it could then become difficult to argue that a single parent publication teaches every element of the same claims.  Nevertheless, if properly managed, such tensions can be overcome and even advantageous.

Finally, a future Section 112 challenge to the chain of priority is something for patent applicants to consider during prosecution.  As discussed above, choices made in prosecution, such as the decision to pursue a CIP, may play a role in the strength of a patent’s chain of priority if challenged in district court or at the PTAB.  Using this lens, patentees should focus on what is new and what is truly within the claim scope, before facing a priority challenge.

Although chain of priority is a highly fact-based inquiry, it may be a worthwhile strategy consideration in the context of IPRs, district court litigations, and even patent prosecution.